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ADDIS ABABA UNIVERSITY ADDIS ABABA INSTITUTE OF TECHNOLOGY SCHOOL OF CIVIL AND ENVIRONMENTAL ENGINEERING
THE DESIGN OF A ROADWAY SECTION FROM ADAMA TO AWASH USING RIGID PAVEMENT AND ITS IMPLICATION IN ETHIOPIAN ROAD CONSTRUCTION By Elias Yilma Kaleab Woldeyohannes Kidus Ayalneh Yonathan Bekele
A Thesis Submitted to the School of Civil and Environmental Engineering in Partial Fulfillment of the Requirement for Degree of Bachelor of Science In Civil Engineering
Advisor Ato Asres Simeneh
June 2014 Addis Ababa, Ethiopia
THE DESIGN OF A ROADWAY SECTION FROM ADAMA TO AWASH USING RIGID PAVEMENT AND ITS IMPLICATION IN ETHIOPIAN ROAD CONSTRUCTION By Elias Yilma Kaleab Woldeyohannes Kidus Ayalneh Yonathan Bekele
A Thesis Submitted to the School of Civil and Environmental Engineering in Partial Fulfillment of the Requirement for Degree of Bachelor of Science In Civil Engineering
Approved by Board of Examiners:
____________________ ________________ _______________ Advisor
Signature
Date
____________________ ________________ _______________ Examiner
Signature
Date
____________________ ________________ _______________ Chair Person
Signature
Date
We, the undersigned, declare that this thesis is our original work performed under the supervision of our research advisor Ato Asres Simeneh. This paperwork has not been presented as a thesis for a degree in any other university. All sources of materials used for this thesis have also been duly acknowledged. Name
Signature
Elias Yilma
_____________
Kaleab Woldeyohannes
_____________
Kidus Ayalneh
_____________
Yonathan Bekele
_____________
Place: Addis Ababa Institute of Technology Addis Ababa University, Addis Ababa, Ethiopia Date: June 16, 2014
Acronyms AACC
Addis Ababa Chamber of Commerce
AADT
Annual Average Daily Traffic
AASHO
American Association of State Highway Officials
AASHTO
American Association of State Highway and Transport Officials
AI
Artificial Intelligence
ASTM
American Standard for Testing Materials
CBR
Californian Bearing Ratio
CI
Construction Industry
DOT
Department of Transportation
ERA
Ethiopian Roads Authority
ESA
Equivalent Single Axle
ESAL
Equivalent Single Axle Load
GTP
Growth and Transformation Plan
IRC
Indian Road Congress
JCP
Jointed Concrete Pavement
JRCP
Jointed Reinforced Concrete Pavement
LISP
LISt Processing
MSA
Million Standard Axles
NCHRP
National Cooperative for Highway
PCA
Portland Cement Association
PCC
Portland Cement Concrete
PROLOG
PROgramming in LOGic
PSI
Present Serviceability Index
RSDP
Road Sector Development Plan
i
Executive Summary This study which is entitled “The Design of a Roadway Section from Adama to Awash using Rigid Pavement and Its Implication in Ethiopian Road Construction” focuses on the actual economic and structural feasibility of constructing rigid pavements instead of the widely popular flexible pavements here in Ethiopia. The Road Sector Development Plan IV has scheduled an excessively large amount of budget for the maintenance and rehabilitation of existing trunk links on the nation’s road network. This thesis tries to prove rigid pavements are actually better in the long run for such major trunk roads that exhibit ever increasing traffic. In the research, the roadway linking Adama and Awash has been designed using both rigid and flexible pavements. Historical traffic count and processed axle load survey have been incorporated to arrive at a realistic number of equivalent standard axles for the years between 2017 and 2057. The rigid pavement design is based on ERA Pavement Design Manual and AASHTO Guide for Design of Pavement Structures. Design periods include twenty, twenty five, thirty, thirty five and forty years whereas subgrade CBR values range from 2% to 90%. In the mean time, major drawbacks of the ERA Pavement Design Manual in terms of design inputs and performance criteria have been pointed out based on the much detailed AASHTO Guide for Design of Pavement Structures. The flexible counterpart has been designed using the The Indian Road Congress Design Manual (IRC 37-2001) for a base period of 17 years. CBR values range from 2% to 30% and then beyond. The remaining 23 years will be addressed through yearly overlay, periodic maintenance and major maintenance. The life cycle cost analysis results based on 1km length show that rigid pavements are by far more economical in designing major trunk roads for periods exceeding 20 years when compared to their flexible counterparts. The advantage doesn’t only lie in saving huge future rehabilitation cost, but also in fast completion of construction, reduced fuel consumption of heavy vehicles and reduced inconvenience to road users due to the absence of regular maintenance operations. For the rigid pavement where subgrade CBR values are less than 30%, a thickness of 150mm subbase beneath PCC slab has proven to be economical. For subgrade CBR value exceeding 30%, a combination of sub-base and capping layer resulting in an equivalent 400mm sub-base thickness is more viable. For subgrade CBR 30%, both approaches can be used interchangeably. Generally speaking, Ethiopia, with the right construction technique and mindset, should consider shifting to rigid pavement in scenarios where such choice offers huge economical and structural advantage.
ii
Acknowledgment We would like to begin by expressing our heartfelt thanks to the Almighty God for all His provision throughout our academic years. Second in line, we thank our advisor Ato Asres Simeneh for his wonderful guidance and advice. It was quite exciting. Lastly, we would like to take this opportunity to mention a few people such as Ato Alemayehu (ERA Research Directorate Director), Ato Melaku Gizachew, Ato Micheal Asseged and Ato Raeed Ali whose cooperation made this thesis possible.
iii
Table of Contents Acronyms ----------------------------------------------------------------------------------------------- i Executive Summary ---------------------------------------------------------------------------------- ii Acknowledgement ------------------------------------------------------------------------------------ iii Chapter 1: Introduction ----------------------------------------------------------------------------- 1 1.1 Introduction -------------------------------------------------------------------------------- 1 1.2 Statement of the Problem ---------------------------------------------------------------- 5 1.3 Objectives and Scope of the Study ----------------------------------------------------- 7 References -------------------------------------------------------------------------------------- 8 Chapter 2: Literature Review ---------------------------------------------------------------------- 9 2.1 Introduction -------------------------------------------------------------------------------- 9 2.2 Design Considerations ------------------------------------------------------------------- 9 2.2.1 Pavement Performance ------------------------------------------------------------ 11 2.2.2 Traffic ------------------------------------------------------------------------------- 12 2.2.2.1 Evaluation of Traffic ------------------------------------------------------- 12 2.2.2.2 Design Traffic Loading ---------------------------------------------------- 13 2.2.3 Roadbed Soil ----------------------------------------------------------------------- 13 2.2.4 Materials of Construction --------------------------------------------------------- 14 2.2.4.1 Sub-base ---------------------------------------------------------------------- 14 2.2.4.2 Pavement Slab --------------------------------------------------------------- 14 2.2.5 Environment ------------------------------------------------------------------------ 16 2.2.6 Drainage ----------------------------------------------------------------------------- 16 2.2.7 Shoulder Design -------------------------------------------------------------------- 16 2.3 Design Requirements--------------------------------------------------------------------- 17 2.3.1 Design Variables ------------------------------------------------------------------- 17 2.3.1.1 Time Constraints ------------------------------------------------------------ 17 2.3.1.2Traffic ------------------------------------------------------------------------- 19 2.3.1.3 Reliability -------------------------------------------------------------------- 20 2.3.1.4 Environmental Impacts ----------------------------------------------------- 22
2.3.2 Performance Criteria -------------------------------------------------------------- 23 2.3.2.1 Serviceability --------------------------------------------------------------- 23 2.3.2.2 Allowable Rutting ---------------------------------------------------------- 24 2.3.2.3 Aggregate Loss ------------------------------------------------------------- 24 2.3.3 Material Properties for Structural Design -------------------------------------- 25 2.3.3.1 Effective Roadbed Soil Resilient Modulus ----------------------------- 25 2.3.3.2 Effective Modulus of Subgrade Reaction ------------------------------- 25 2.3.3.3 Pavement Layer Materials Characterization ---------------------------- 25 2.3.3.4 PCC Modulus of Rupture ------------------------------------------------- 26 2.3.3.5 Layer Coefficients ---------------------------------------------------------- 26 2.3.4 Pavement Structural Characteristics -------------------------------------------- 26 2.3.4.1 Drainage ---------------------------------------------------------------------- 26 2.3.4.2 Load Transfer --------------------------------------------------------------- 27 2.3.4.3 Loss of Support (LS) ------------------------------------------------------- 28 2.3.5 Reinforcement Variables---------------------------------------------------------- 28 2.3.5.1 Jointed Concrete Pavements ---------------------------------------------- 29 2.3.5.2 Continuously Reinforced Concrete Pavements ------------------------ 29 2.4 Economic Analysis ----------------------------------------------------------------------- 31 2.4.1 Economical Implications of Using Rigid Pavement -------------------------- 31 2.4.1.1 Initial Cost-------------------------------------------------------------------- 31 2.4.1.2 Future Maintenance Expenditure Prediction ---------------------------- 32 2.4.1.3 Rolling Resistance and Fuel Consumption ------------------------------ 32 2.4.1.4 Early Completion ----------------------------------------------------------- 32 2.4.2 How to Analyze Pavement Costs ------------------------------------------------ 33 2.4.3 Factors Involved in Pavement Costs and Benefits ---------------------------- 33 2.4.4 Economic Comparison of Rigid and Flexible Pavements ------------------- 35 2.4.5 Cautions in Using LCCA --------------------------------------------------------- 36 2.4.6 Methods of Economic Analysis ------------------------------------------------- 37 References --------------------------------------------------------------------------------- 38
Chapter 3: Research Methodology & Procedures --------------------------------------------- 40 3.1 Introduction -------------------------------------------------------------------------------- 40 3.2 AASHTO Design Procedure for Rigid Pavement Design -------------------------- 41 3.2.1 Subgrade Reaction: k-value ------------------------------------------------------ 41 3.2.2 Slab Thickness --------------------------------------------------------------------- 46 3.2.3 Joint Design ------------------------------------------------------------------------- 50 3.2.3.1 Joint Types ------------------------------------------------------------------- 50 3.2.3.2 Joint Geometry -------------------------------------------------------------- 50 3.2.4 Rigid Pavement Reinforcement Design ---------------------------------------- 51 3.3 ERA Design Procedures for Rigid Pavement ----------------------------------------- 52 3.3.1 Design life -------------------------------------------------------------------------- 52 3.3.2 Design Traffic Loading ----------------------------------------------------------- 53 3.3.3 Thickness Design ------------------------------------------------------------------ 53 3.3.3.1 Capping and Sub-base ------------------------------------------------------ 53 3.3.3.2 Concrete Slab Thickness and Reinforcement --------------------------- 54 3.3.4 Design for Movement ------------------------------------------------------------- 56 3.3.4.1 Transverse Joint Spacing --------------------------------------------------- 56 3.3.4.2 Longitudinal Joint Spacing ------------------------------------------------ 56 3.3.5 Design Detailing ------------------------------------------------------------------- 56 3.4 Unit Rate Estimation Procedures ------------------------------------------------------- 57 3.4.1 Preliminary Works of Pavement Alternatives --------------------------------- 57 3.4.1.1 Site Clearance --------------------------------------------------------------- 57 3.4.1.2 Earthwork -------------------------------------------------------------------- 58 3.4.1.3 Sub base Works ------------------------------------------------------------- 58 3.4.1.4 Structures --------------------------------------------------------------------- 58 3.4.1.5 Drainage Provisions -------------------------------------------------------- 58 3.4.1.6 Miscellaneous and Ancillary Works ------------------------------------- 58 3.4.2 Base course and AC Works [For Flexible Pavements] ----------------------- 59 3.4.2.1 Base course------------------------------------------------------------------- 59
3.4.2.2Asphalt Concrete ------------------------------------------------------------- 59 3.4.3 Cement Concrete Slab Works [For Rigid Pavements] ------------------- 59 3.5 Programming ------------------------------------------------------------------------------ 59 References -------------------------------------------------------------------------------------- 61 Chapter 4: Research Data --------------------------------------------------------------------------- 62 4.1Acquired Secondary Data ---------------------------------------------------------------- 62 4.2 Reasonably Justified Complementary Data ------------------------------------------- 70 References -------------------------------------------------------------------------------------- 71 Chapter 5: Analysis and Discussion--------------------------------------------------------------- 72 5.1 Introduction -------------------------------------------------------------------------------- 72 5.2 Traffic Analysis --------------------------------------------------------------------------- 73 5.2.1 Design Period ----------------------------------------------------------------------- 73 5.2.2Traffic Volume ---------------------------------------------------------------------- 74 5.2.2.1 Traffic Growth, g ------------------------------------------------------------ 75 5.2.2.2 Directional Distribution Factor, DD -------------------------------------- 77 5.2.2.3 Lane Distribution Factor, DL ---------------------------------------------- 77 5.2.2.4 Determination of Annual Average Daily Traffic and Cumulative Number of Traffic -------------------------------------------------------------------- 78 5.2.2.5 Axle Loads ------------------------------------------------------------------- 82 5.2.2.6 Determination of Truck Factors ------------------------------------------ 88 5.2.2.7 Cumulative Equivalent Standard Axles ---------------------------------- 96 5.3 Subgrade Soil CBR ----------------------------------------------------------------------- 100 5.4 Rigid Pavement Design (JRCP) According to ERA, 2002 ------------------------- 101 5.4.1 20 years Design Period ------------------------------------------------------------ 101 5.4.2 25, 30, 35 and 40 years Design Period ------------------------------------------ 104 5.5 Rigid Pavement Design (JRCP) as per AASHTO, 1993 ---------------------------- 110 5.5.1 Effective Modulus of Subgrade Reaction (k-value) -------------------------- 110 5.5.1.1 Input Variables -------------------------------------------------------------- 110 5.5.1.2 Seasonal Resilient Roadbed Modulus ------------------------------------ 111
5.5.1.3 Sub-base Elastic Resilient Modulus, ESB -------------------------------- 112 5.5.1.4 Composite Modulus of Subgrade Reaction, k ------------------------- 113 5.5.2 Thickness Design ------------------------------------------------------------------ 116 5.5.3 PCC Slab Thickness Design with Revised Sub-base Thickness of 400 mm – 15.75 inches – Which also Includes Capping Layer --------------------------------- 120 5.5.4 Joint Design ------------------------------------------------------------------------- 124 5.5.4.1 Joint Types ------------------------------------------------------------------- 124 5.5.4.2 Joint Geometry -------------------------------------------------------------- 124 5.5.5 Rigid Pavement Reinforcement Design ---------------------------------------- 124 5.5.5.1 Slab Reinforcement --------------------------------------------------------- 124 5.5.5.2 Tie Bars ----------------------------------------------------------------------- 133 5.5.5.3 Dowel Bars ------------------------------------------------------------------- 134 5.6 Comparison of the Rigid Pavement Design using ERA Manual and AASHTO Guide ------------------------------------------------------------------------------- 134 5.7 Flexible Pavement Design as per IRC Design Manual ------------------------------ 139 5.7.1 Flexible Pavement Design Adjustment ----------------------------------------- 145 5.7.2 Pavement Materials Specification ----------------------------------------------- 145 5.8 Alternative Design ------------------------------------------------------------------------ 145 5.8.1 Rigid Pavement Alternative ------------------------------------------------------ 146 5.8.1.1 Thickness Design ----------------------------------------------------------- 147 5.8.1.2 Slab Reinforcement Design------------------------------------------------ 150 5.8.2 Flexible Pavement Alternative Design------------------------------------------ 157 5.9 Unit Rate Analysis ------------------------------------------------------------------------ 161 5.9.1 Labor Rates ------------------------------------------------------------------------ 161 5.9.2 Material Rates ---------------------------------------------------------------------- 162 5.9.3 Equipment Rates ------------------------------------------------------------------- 163 5.10 Economic Analysis---------------------------------------------------------------------- 163 5.10.1 Rigid Pavement ------------------------------------------------------------------ 163 5.10.1.1 Initial Investment ---------------------------------------------------------- 163
5.10.1.2 Maintenance and Rehabilitation Costs --------------------------------- 171 5.10.1.3 Total Cost (Initial + Maintenance) -------------------------------------- 174 5.10.2 Flexible Pavement ---------------------------------------------------------------- 178 5.10.2.1 Initial Investment ---------------------------------------------------------- 178 5.10.2.2 Future Incurred Costs ----------------------------------------------------- 180 5.10.2.3 Total Incurred Costs ------------------------------------------------------- 181 5.10.3 Comparison between Flexible and Rigid Pavements ----------------------- 185 References ------------------------------------------------------------------------------------- 188 Chapter 6: Implication in Ethiopian Road Construction ------------------------------------ 190 6.1 Introduction -------------------------------------------------------------------------------- 190 6.2 Economic Feasibility --------------------------------------------------------------------- 190 6.2.1 Initial Investment Expenditure --------------------------------------------------- 190 6.2.1.1 High Volume Roads (The Case Study Picked) ------------------------- 190 6.2.1.2 Low Volume Roads --------------------------------------------------------- 191 6.2.2 Life Cycle Cost --------------------------------------------------------------------- 191 6.2.3 Total Cost --------------------------------------------------------------------------- 191 6.3 Ease and Quality of Construction ------------------------------------------------------ 191 6.4 Conclusion and Recommendations ---------------------------------------------------- 192 Appendix A: Program Description and Organization -------------------------------------------- 193 Appendix B: Program Structure --------------------------------------------------------------------- 195 Appendix C: Algorithms ----------------------------------------------------------------------------- 199 Appendix D: User Manual --------------------------------------------------------------------------- 207 Appendix E: An Implementation in Common Lisp ---------------------------------------------- 210 Appendix F: Cost Breakdown, Takeoff and BOQ ------------------------------------------------ 233 Appendix G: Economic Detail of Flexible Pavement -------------------------------------------- 239 Appendix H: Typical Flexible Pavement Section ------------------------------------------------ 250 Appendix I: Typical Rigid Pavement Section ----------------------------------------------------- 251
List of Tables Table 1.1: Comparison of Rigid Pavement with Flexible Pavement ---------------------- 4 Table 2.1: Equivalency Factors for Axle Loads, Rigid Pavements ------------------------ 13 Table 2.2: Guide lines for Analysis Period ---------------------------------------------------- 19 Table 2.3: Guide lines for Lane Distribution Factor, DL ------------------------------------ 20 Table 2.4: Suggested Levels of Reliability for Various Functional Classifications ----- 22 Table 2.5: General Guidelines for minimum levels of pt ----------------------------------- 23 Table 2.6: different drainage levels from the pavement structure -------------------------- 27 Table 2.7: Recommended Values of Drainage Coefficient, Cd, for Rigid Pavement Design --------------------------------------------------------------------------- 27 Table 2.8: Costs Typically Considered in Life-Cycle Cost Analysis ---------------------- 33 Table 3.1: Recommended Values for Sub-base and Subgrade Materials ----------------- 51 Table 4.1: Annual Average Daily Traffic of the paved Trunk Road from Adama (Nazareth) to Awash------------------------------------------------------------------------------- 62 Table 4.2: Summary of Daily Traffic on ERA Network (1994–2004) -------------------- 62 Table 4.3: Traffic Growth Rate Considered in Re-alignment of Beseka Crossing ------ 63 Table 4.4: Truck Factors based on actual Vehicles on the Design Lane ------------------ 67 Table 4.5: Comparison of Truck Factors (Source: Consultancy Service for the Detailed Engineering Design for Beseka Crossing ------------------------------------------------------ 67 Table 4.6: Values of Truck Factors Employed ----------------------------------------------- 68 Table 4.7: Summary of Test Results for Natural Gravel Course --------------------------- 68 Table 4.8: Unit Rates of Pavement Structure Component Materials of Rigid Pavements and Flexible Pavements --------------------------------------------------------------------------- 69 Table 4.9: Factors to be used for estimation of AADT in the opening year and cumulative traffic at the end of design period --------------------------------------------------------------- 70 Table 4.10: Values of design inputs used for the design of Rigid Pavement ------------- 70 Table 5.1: Annual Average Daily Traffic of the paved Trunk Road from Adama (Nazareth) to Awash ------------------------------------------------------------------------------ 74 Table 5.2: Summary of Daily Traffic on ERA Network (1994–2004) -------------------- 76 Table 5.3: Traffic Growth Rate Considered in Re-alignment of Beseka Crossing ------ 77
Table 5.4: Factors to be used for estimation of AADT in the opening year and cumulative traffic at the end of design period --------------------------------------------------------------- 78 Table 5.5: Estimation of AADT in the opening year and cumulative traffic at the end of the design period ----------------------------------------------------------------------------------- 79 Table 5.6: AADT and Cumulative number of cars exhibited on the segment during the base period ------------------------------------------------------------------------------------------ 79 Table 5.7: AADT and Cumulative number of Buses exhibited on the segment during the base period ------------------------------------------------------------------------------------------ 80 Table 5.8: AADT and Cumulative number of Trucks exhibited on the segment during the base period ------------------------------------------------------------------------------------------ 81 Table 5.9: AADT and Cumulative number of Articulated Trucks exhibited on the segment during the base period ------------------------------------------------------------------ 81 Table 5.10: Front and Rear Axle Load Distribution of Different Vehicle Categories with their Percentage Probability of Occurrence ---------------------------------------------------- 86 Table 5.11: Traffic Survey Result Acquired in the Re-alignment of Beseka Crossing - 87 Table 5.12: Truck Factors based on actual Vehicles on the Design Lane (Use in combination with Figure 5.2 to understand the axle configuration) ------------------------ 89 Table 5.13: Comparison of Truck Factors of Different Road Projects ------------------- 89 Table 5.14: Values of Truck Factors Employed ---------------------------------------------- 90 Table 5.15: Comparison of Flexible and Rigid Pavement Equivalency Factors of ERA ------------------------------------------------------------------------------------ 91 Table 5.16: Comparison of Flexible and Rigid Pavement Equivalency Factors of AASHTO ------------------------------------------------------------------------------------------- 94 Table 5.17: Cumulative Standard Axles of the Roadway at the 20th year Base Period of Rigid Pavements ----------------------------------------------------------------------------------- 96 Table 5.18: Equivalent Number of Single Axles for Bus along the years of the Base Period ------------------------------------------------------------------------------------------------ 97 Table 5.19: Equivalent Number of Single Axles for Trucks along the years of the Base Period ------------------------------------------------------------------------------------------------ 97 Table 5.20: Equivalent Number of Single Axles for Truck-Trailers along the years of the Base Period ----------------------------------------------------------------------------------------- 98 Table 5.21: Total Number of Equivalent Single Axles for all vehicles along the years of the Base Period ------------------------------------------------------------------------------------- 99 Table 5.22: Summary of Total Number of Equivalent Single Axles for all vehicles along the years of the Base Period ---------------------------------------------------------------------- 99
Table 5.23: Subgrade CBR at Lake Beseka and Metehara ---------------------------------- 100 Table 5.24: Capping Layer, Sub-base and Slab thicknesses as well as longitudinal reinforcement (175 msa) -------------------------------------------------------------------------- 102 Table 5.25: Additional thicknesses where there is no lateral Support (175 msa) -------- 104 Table 5.26: Cumulative Number of Vehicles for the Design Periods of 25, 30, 35 and 40 years ------------------------------------------------------------------------------------------------- 105 Table 5.27: Cumulative Million Standard Axles in the Design Periods of 25, 30, 35 and 40 years ---------------------------------------------------------------------------------------------- 105 Table 5.28: Capping Layer, Sub-base and Slab thicknesses and as well as longitudinal reinforcement (198 msa) -------------------------------------------------------------------------- 106 Table 5.29: Additional Thicknesses where there is no lateral support (198 msa) ------- 106 Table 5.30: Capping Layer, Sub-base and Slab thicknesses and as well as longitudinal reinforcement (251 msa) -------------------------------------------------------------------------- 107 Table 5.31: Additional Thicknesses where there is no lateral support (251 msa) ------- 107 Table 5.32: Capping Layer, Sub-base and Slab thicknesses and as well as longitudinal reinforcement (310 msa) -------------------------------------------------------------------------- 108 Table 5.33: Additional Thicknesses where there is no lateral support (310 msa) ------- 108 Table 5.34: Capping Layer, Sub-base and Slab thicknesses and as well as longitudinal reinforcement (374 msa) -------------------------------------------------------------------------- 109 Table 5.35: Additional Thicknesses where there is no lateral support (374 msa) ------- 109 Table 5.36: Road Bed Resilient Modulus and relative Damage for Dry and Wet Seasons ------------------------------------------------------------------------------ 112 Table 5.37: Composite (Effec.) k-value, relative damage and corrected k-value for LS = 1.5 -------------------------------------------------------------------------------------------------- 116 Table 5.38: The Estimated Future Traffic, W18, in the Design Period --------------------- 116 Table 5.39: Slab Thicknesses for different Design Periods but for Constant Small Subbase Thickness of 150mm and no Capping Layer -------------------------------------------- 119 Table 5.40: Composite (Effec.) k-value, relative damage and corrected k-value for LS = 1.5 ---------------------------------------------------------------------------------------------------- 122 Table 5.41: Slab Thicknesses for different Design Periods for Constant Sub-base Thickness of 400mm with Capping Layer ----------------------------------------------------- 123 Table 5.42: Recommended Values for Sub-base and Subgrade ---------------------------- 125 Tables 5.43: Reinforcement Computation of The PCC Slabs for 400 mm Sub-base Thickness Longitudinal (Short) and Transverse (Long) Directions – 175 msa ----------- 126
Tables 5.44: Reinforcement Computation of The PCC Slabs for 400 mm Sub-base Thickness Longitudinal (Short) and Transverse (Long) Directions – 198 msa ----------- 126 Tables 5.45: Reinforcement Computation of The PCC Slabs for 400 mm Sub-base Thickness Longitudinal (Short) and Transverse (Long) Directions – 251 msa ----------- 127 Tables 5.46: Reinforcement Computation of The PCC Slabs for 400 mm Sub-base Thickness Longitudinal (Short) and Transverse (Long) Directions – 310 msa ----------- 128 Tables 5.47: Reinforcement Computation of The PCC Slabs for 400 mm Sub-base Thickness Longitudinal (Short) and Transverse (Long) Directions – 374 msa ----------- 128 Tables 5.48: Reinforcement Computation of The PCC Slabs for 150 mm Sub-base Thickness Longitudinal (Short) and Transverse (Long) Directions – 175 msa ----------- 129 Tables 5.49: Reinforcement Computation of The PCC Slabs for 150 mm Sub-base Thickness Longitudinal (Short) and Transverse (Long) Directions – 198 msa ----------- 130 Tables 5.50: Reinforcement Computation of The PCC Slabs for 150 mm Sub-base Thickness Longitudinal (Short) and Transverse (Long) Directions – 251 msa ----------- 130 Tables 5.51: Reinforcement Computation of The PCC Slabs for 150 mm Sub-base Thickness Longitudinal (Short) and Transverse (Long) Directions – 310 msa ----------- 131 Tables 5.52: Reinforcement Computation of The PCC Slabs for 150 mm Sub-base Thickness Longitudinal (Short) and Transverse (Long) Directions – 374 msa ----------- 132 Table 5.53: Comparison of Rigid Pavement Design using ERA and AASHTO --------- 135 Table 5.54: Flexible Pavement Design for CBR 2 % and 17 Years Design Period ----- 140 Table 5.55: Flexible Pavement Design for CBR 3 % and 17 Years Design Period ----- 141 Table 5.56: Flexible Pavement Design for CBR 4 % and 17 Years Design Period ----- 141 Table 5.57: Flexible Pavement Design for CBR 5 % and 17 Years Design Period ----- 142 Table 5.58: Flexible Pavement Design for CBR 6 % and 17 Years Design Period ----- 142 Table 5.59: Flexible Pavement Design for CBR 7 % and 17 Years Design Period ----- 143 Table 5.60: Flexible Pavement Design for CBR 8 % and 17 Years Design Period ----- 143 Table 5.61: Flexible Pavement Design for CBR 9 % and 17 Years Design Period ----- 144 Table 5.62: Flexible Pavement Design for CBR 10 % and 17 Years Design Period ---- 144 Table 5.63: Cumulative Number of Standard Axles for Different Design Years of the Four-Lane, Two-Way Proposed Road ---------------------------------------------------------- 146 Table 5.64: Cumulative Number of Standard Axles of the Four-Lane, Two-Way Proposed Road (150 mm sub-base thickness) ------------------------------------------------- 148 Table 5.65: Cumulative Number of Standard Axles of the Four-Lane, Two-Way Proposed Road (400 mm combined sub-base thickness) ------------------------------------ 149
Tables 5.66: Reinforcement Computation of the PCC Slabs for 400 mm Sub-base Thickness in Longitudinal (Short) and Transverse (Long) Directions – 140 msa -------- 150 Tables 5.67: Reinforcement Computation of the PCC Slabs for 400 mm Sub-base Thickness in Longitudinal (Short) and Transverse (Long) Directions – 159 msa -------- 151 Tables 5.68: Reinforcement Computation of the PCC Slabs for 400 mm Sub-base Thickness in Longitudinal (Short) and Transverse (Long) Directions – 201 msa -------- 151 Tables 5.69: Reinforcement Computation of the PCC Slabs for 400 mm Sub-base Thickness in Longitudinal (Short) and Transverse (Long) Directions – 247 msa -------- 152 Tables 5.70: Reinforcement Computation of the PCC Slabs for 400 mm Sub-base Thickness in Longitudinal (Short) and Transverse (Long) Directions – 299 msa -------- 153 Tables 5.71: Reinforcement Computation of the PCC Slabs for 150 mm Sub-base Thickness in Longitudinal (Short) and Transverse (Long) Directions – 140 msa -------- 153 Tables 5.72: Reinforcement Computation of the PCC Slabs for 150 mm Sub-base Thickness in Longitudinal (Short) and Transverse (Long) Directions – 159 msa -------- 154 Tables 5.73: Reinforcement Computation of the PCC Slabs for 150 mm Sub-base Thickness in Longitudinal (Short) and Transverse (Long) Directions – 201 msa -------- 155 Tables 5.74: Reinforcement Computation of the PCC Slabs for 150 mm Sub-base Thickness in Longitudinal (Short) and Transverse (Long) Directions – 247 msa -------- 155 Tables 5.75: Reinforcement Computation of the PCC Slabs for 150 mm Sub-base Thickness in Longitudinal (Short) and Transverse (Long) Directions – 299 msa -------- 156 Table 5.76: Flexible Pavement Design for CBR 2% and 20 Years Design Period ------ 157 Table 5.77: Flexible Pavement Design for CBR 3% and 20 Years Design Period ------ 157 Table 5.78: Flexible Pavement Design for CBR 4% and 20 Years Design Period ------ 158 Table 5.79: Flexible Pavement Design for CBR 5% and 20 Years Design Period ------ 158 Table 5.80: Flexible Pavement Design for CBR 6% and 20 Years Design Period ------ 159 Table 5.81: Flexible Pavement Design for CBR 7% and 20 Years Design Period ------ 159 Table 5.82: Flexible Pavement Design for CBR 8% and 20 Years Design Period ------ 160 Table 5.83: Flexible Pavement Design for CBR 9% and 20 Years Design Period ------ 160 Table 5.84: Flexible Pavement Design for CBR 10% and 20 Years Design Period ---- 161 Table 5.85: Initial Investment costs of Rigid Pavements for 2014 and 2017 ------------- 164 Table 5.86: Initial Investment costs of Rigid Pavements for 2014 and 2017------------- 164 Table 5.87: Initial Investment costs of Rigid Pavements for 2014 and 2017 ------------- 165 Table 5.88: Initial Investment costs of Rigid Pavements for 2014 and 2017 ------------- 166 Table 5.89: Initial Investment costs of Rigid Pavements for 2014 and 2017 ------------- 166
Tables 5.90 and 5.91: Past and forecasted inflation values of Ethiopia ------------------ 170 Table 5.92: Maintenance and Rehabilitation Methods that shall be considered for Rigid Pavements and their Expected Life ------------------------------------------------------------- 171 Table 5.93: Maintenance Costs of the Rigid Pavement at Different Intervals Until 2057 (40 years design Period (as of 2017) ------------------------------------------------------------ 172 Table 5.94: Total Maintenance and Rehabilitation Costs at 20, 25, 30, 35 and 40 Years of Design Periods (in Birr) --------------------------------------------------------------------------- 173 Table 5.95 to 5.99: Total Cost (Construction + Maintenance) of Rigid Pavements for different design periods --------------------------------------------------------------------------- 175 Table 5.100: Trend in thickness variation as CBR value varies ---------------------------- 179 Table 5.101: Initial Investment for different CBR values ---------------------------------- 179 Table 5.102: Different Recurring Costs (Source: ERA, Procurement Division) --------- 180 Table 5.103: Expenditure in Future Value with respect to 2017 at selected years ------ 181 Table 5.104: Expenditure in Future Value with respect to 2017 at selected years ------ 181 Table 5.105: Expenditure in Future Value with respect to 2017 at selected years ------- 181 Table 5.106: Expenditure in Future Value with respect to 2017 at selected years ------ 182 Table 5.107: Expenditure in Future Value with respect to 2017 at selected years ------ 182 Table 5.108: Expenditure in Future Value with respect to 2017 at selected years ------ 182 Table 5.109: Expenditure in Future Value with respect to 2017 at selected years ------ 183 Table 5.110: Expenditure in Future Value with respect to 2017 at selected years ------ 183 Table 5.111: Expenditure in Future Value with respect to 2017 at selected years ------ 183 Table 5.112: Expenditure in Future Value with respect to 2017 at selected years ------ 184 Table 5.113: Expenditure in Future Value with respect to 2017 at selected years ------ 184 Table 5.114: Expenditure in Future Value with respect to 2017 at selected years ------ 184
List of Figures Figure 1.1: Layers with in a Typical Flexible Pavement ---------------------------------------- 2 Figure 1.2: Layers with in a Typical Rigid Pavement ------------------------------------------- 3 Figure 1.3: Load Distribution of Wheel Load to Pavement Layers ---------------------------- 4 Figure 3.1: Chart for Composite Modulus of Subgrade Reaction, k ------------------------- 43 Figure 3.2: Chart to Modify Modulus of Subgrade Reaction to Consider Effects of Rigid Foundation near Surface ------------------------------------------------------------------------------ 44 Figure 3.3: Chart for Estimating Relative Damage to Rigid Pavements Based on Slab Thickness and underlying Support ------------------------------------------------------------------------------- 45 Figure 3.4: Chart for Correction of Effective Modulus of Subgrade Reaction for Potential Loss of Sub-base Support ----------------------------------------------------------------------------------- 46 Figure 3.5: Design Chart for Rigid Pavement, Segment 1 -------------------------------------- 48 Figure 3.6: Design Chart for Rigid Pavement, Segment 2 -------------------------------------- 49 Figure 3.7: Reinforcement Design Chart for Jointed Reinforced Concrete Pavements ---- 52 Figure 3.8: Capping Layer and Sub-base Thickness (mm) design ---------------------------- 54 Figure 3.9: Concrete Slab Thickness design ------------------------------------------------------ 55 Figure 3.10: Additional Concrete Slab Thickness without Lateral Support ------------------ 56 Figure 4.1: Front Axle Load distribution of Buses ---------------------------------------------- 63 Figure 4.2: Rear Axle Load distribution of Buses ------------------------------------------------ 63 Figure 4.3: Front Axle Load distribution of Trucks ---------------------------------------------- 64 Figure 4.4: Rear Axle Load distribution of Trucks ----------------------------------------------- 64 Figure 4.5: Axle Load distribution of Truck Trailers (Articulated Type) --------------------- 65 Figure 4.6: Load Composition of Vehicles on the Design Lane -------------------------------- 65 Figure 4.7: Nomenclature of Articulated Trucks ------------------------------------------------- 66 Figure 5.1: Map depicting the Road Segment ---------------------------------------------------- 84 Figure 5.2: Nomenclature of Articulated Trucks ------------------------------------------------- 85 Figure 5.3: Load Composition of Vehicles on the Design Lane Measured in Re-alignment of Beseka Crossing --------------------------------------------------------------------------------------- 87
Figure 5.4: Plot of the Equivalency Factors of Flexible & Rigid Pavements vs. their Respective Axle Loads (ERA, 2002) ------------------------------------------------------------------------------ 93 Figure 5.5: Plot of the Ratio of Equivalency Factors Rigid & Flexible Pavements vs. Axle Loads (ERA, 2002) -------------------------------------------------------------------------------------------- 93 Figure 5.6: Plot of the Equivalency Factors of Flexible & Rigid Pavements vs. their Respective Axle Loads (AASHTO, 1993) ------------------------------------------------------------------------ 95 Figure 5.7: Plot of the Ratio of Equivalency Factors Rigid & Flexible Pavements vs. Axle Loads (AASHTO, 1993) -------------------------------------------------------------------------------------- 95 Figure 5.8: Capping Layer, Sub-base and Slab thicknesses as well as longitudinal reinforcement --------------------------------------------------------------- 103 Figure 5.9: Obtaining Composite Subgrade Modulus of Reaction ----------------------------- 113 Figure 5.10: Graphical Determination of Relative Damage, Uf, from the Corresponding Composite Subgrade Reaction ----------------------------------------------------------------------- 114 Figure 5.11: Corrected k-value of LS = 1.5 (Unbound Granular Material of No Swelling Subbase) --------------------------------------------------------------------------------------------------- 115 Figure 5.12: Determination of Composite Subgrade Modulus of Reaction ------------------- 120 Figure 5.13: Corrected k-value for LS = 1.5 (Unbound Granular Material of Non Swelling Subbase) --------------------------------------------------------------------------------------------------- 121 Figure 5.14: Reinforcement Design Chart for Jointed Reinforced Concrete Pavements --- 125 Figure 5.15: Recommended Maximum Tie Bar Spacing for PCC Pavements assuming ½ inch Diameter Tie Bars, Grade 40 Steel, and Subgrade Friction Factor of 1.5 --------------------- 133 Figure 5.16: Plot of Cumulative Equivalent Standard Axle Loads vs. Year ------------------ 140 Figure 5.17: Initial Investment costs of Rigid Pavements for 2014 in Birr/km -------------- 168 Figure 5.18: Initial Investment costs of Rigid Pavements for 2017 in Birr/km -------------- 169 Figure 5.19: Maintenance Costs (as of 2017) of the Rigid Pavement in different Design Periods ------------------------------------------------------------------------------------------ 174 Figure 5.20: Total Costs (as of 2017) of the Rigid Pavement in different Design Periods - 178 Figure 5.21: CBR VS Initial Investment Graph (Investment at 2014) ------------------------- 180 Figure 5.22: Comparison of Different Costs of the two Pavement Alternatives (as of 2017) for 20 years Design Period ------------------------------------------------------------------------------- 185 Figure 5.23: Comparison of Different Costs of the two Pavement Alternatives (as of 2017) for 25 years Design Period -------------------------------------------------------------------------------- 185
Figure 5.24: Comparison of Different Costs of the two Pavement Alternatives (as of 2017) for 30 years Design Period -------------------------------------------------------------------------------- 186 Figure 5.25: Comparison of Different Costs of the two Pavement Alternatives (as of 2017) for 35 years Design Period -------------------------------------------------------------------------------- 186 Figure 5.26: Comparison of Different Costs of the two Pavement Alternatives (as of 2017) for 40 years Design Period -------------------------------------------------------------------------------- 187
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
CHAPTER ONE INTRODUCTION 1.1 Introduction The formation of any nation’s transportation system is not at all the result of some master grand plan but rather an evolutionary one. A typical system, now in place, is the synergy of many individual decisions that have been passed on regarding how to connect two or more places of importance. The decisions made include extensive construction of different structures such as: bridges, highways, tunnels, harbors, railway stations and airport runways. According to Nicholas J. Garber & Lester A. Hoel (2009), the transportation planning process comprises seven basic elements, which are interrelated but not necessarily carried out sequentially. The information acquired in one phase of the process may be helpful in earlier or later phases, so there is a continuity of effort that should eventually result in a decision. The elements in the process are: Situation definition, Problem definition, Search for solutions, Analysis of performance, Evaluation of alternatives, Choice of project, Specification and Construction. Furthermore, other factors may rightfully justify a transportation project. Some include prospective improvements in traffic flow and safety, energy consumption, travel time, economic growth and accessibility. [1] And Road transportation is of paramount importance among transportation means because of reasons related to: lower energy consumption, accessibility, affordability, linkage to light industries and lower physical constraints. Once any roadway proves to be an absolute necessity, its approval will be followed by the relevant route investigation, route selection, design, construction and procurement for use. Of course, future maintenance and rehabilitation, if ruled necessary by professionals, come into the picture. Highway design involves putting certain geometrics and pavement structures of any specific project into a realistic perspective. The design stage naturally succeeds the transportation planning stage but precedes construction. A highway pavement is composed of a system of overlaid strata of chosen processed materials that is positioned on the in situ soil, termed the subgrade (Martin Rogers, 2003). Its basic requirement is the provision of a uniform skid resistant running surface with adequate life and requiring minimum maintenance. The chief structural purpose of the pavement is the support of vehicle wheel loads applied to the carriageway and their distribution to the subgrade immediately underneath. If the road is in cut, the subgrade will 1 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
consist of the in-situ soil. If it is constructed on fill, the top layers of the embankment structure are collectively termed as subgrade. The pavement designer must develop the most economical combination of layers that will guarantee the adequate dispersion of incident wheel stresses so that each layer in the pavement does not become overstressed during the design life of the highway. The major variables in the design of a highway pavement are: The thickness of each layer, The material contained within each layer, The type of vehicles in the traffic stream, The volume of traffic predicted to use the highway over its design life and The strength of the underlying subgrade soil. There are three basic components of a highway pavement: Foundation: Consists of the native subgrade soil and the layer of graded stone (sub-base and possibly capping). The function of the sub-base and capping is to provide a platform on which road base can be placed and insulate the subgrade below it against the effects of weather. These layers can form a temporarily usable road surface during construction. Road base: The main structural layer basically required in flexible pavements (Figure 1.1), whose main function is to withstand the applied wheel stresses and distribute them in such a manner that the materials beneath it do not become overloaded.
Figure 1.1: Layers with in a Typical Flexible Pavement (Source: Martin Rogers, 2003) Surfacing: It combines good riding quality with adequate skid resistance. In the meantime, it also minimizes the infiltration of water into the pavement structure, thus preventing associated consequent surface cracks. Texture and durability are vital requirements of a good pavement surface as are surface regularity and flexibility. For flexible pavements, it is normally applied in two layers – base course and wearing course – with the base course being an extension of the road base layer (Figure 1.1) but providing a regulating course on which the final layer (wearing course) is applied. In the case of rigid pavements, the
2 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
structural functions of both the road base and surfacing layers are integrated within the concrete slab (Figure 1.2). [2]
Figure 1.2: Layers with in a Typical Rigid Pavement (Source: Martin Rogers, 2003) Comparison between Flexible and Rigid Pavements Pavement alternatives differ in many aspects when comes to design parameters, strength, load transfer, performance, surface condition, life cycle, weather resistance, initial & maintenance cost etc. But by default, without due investigation and assessment, flexible pavements are used almost all the time, especially in countries like ours despite inevitable doubts about their suitability and cost implications under different conditions. The two most important parameters governing the design of flexible pavement happen to be soil subgrade California Bearing Ratio (CBR) and traffic loading in terms of million standard axles (msa). For the design of rigid pavements, modulus of sub-grade reaction, k will replace the CBR term in flexible pavements (of course with a number of additional design requirements other than these (see Chapters 2 & 3)). Rigid pavements: commonly distribute wheel loads over a wide area of the subgrade as shown on the left side of Figure 1.3 and consist generally of cement concrete and may be reinforced with steel. Reinforcement may be absent in plain concrete pavement. Important factors about rigid type are: Design life typically 30+ years Higher equivalent unit cost Lower maintenance costs High flexural strength Strength of road less dependent on strength of sub-grade Low ability to expand & contract with temperature and therefore need expansion joint High ability to bridge imperfections in sub-grade Flexible pavements typically distribute wheel loads to lower layers of the pavement section as shown on the right side Figure 1.3 and consist generally of bituminous material. Flexible pavement characteristics include: Design life typically 10 – 20 years Lower equivalent unit cost 3 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Costs tied closely to price of oil Higher maintenance costs Low flexural strength Strength of road highly dependent on strength of sub-grade High ability to expand and contract with temperature and do not need expansion joints Low ability to bridge imperfections in sub-grade
Figure 1.3: Load Distribution of Wheel Load to Pavement Layers
Table 1.1: Comparison of Rigid Pavement with Flexible Pavement
1. 2. 3. 4.
Flexible Pavements Deformation in the sub grade is transferred to the upper layers Design is based on load distributing characteristics of the component layers Have low flexural strength Load is transferred by grain to grain contact
5. Have low completion cost but repairing cost is high 6. Have low life span (High Maintenance Cost) 7. Surfacing cannot be laid directly on the sub grade but a sub base is needed 8. No thermal stresses are induced as the pavement have the ability to contract and expand freely 9. Joints are not needed 10. Strength of the road is highly dependent on the strength of the sub grade 11. Rolling of the surfacing is needed 12. Road can be used for traffic within 24 hrs 13. Force of friction is low 14. Damaged by Oils and Certain Chemicals
Rigid Pavements 1. Deformation in the subgrade is not transferred to subsequent layers 2. Design is mainly based on flexural strength or slab action 3. Have high flexural strength 4. No such phenomenon of grain to grain load transfer exists 5. Have low repairing cost but completion cost is high 6. Life span is more as compare to flexible (Low Maintenance Cost) 7. Surfacing can be directly laid on the sub grade 8. Thermal stresses are more vulnerable to be induced as the ability to contract and expand is very less in concrete 9. Joints are needed 10. Strength of the road is less dependent on the strength of the sub grade 11. Rolling of the surfacing in not needed 12. Road can’t be used until 14 curing days 13. Force of friction is high 14. No Damage by Oils and Greases 4
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 1.1 can be enough to designate the basic differences between the two universally recognized pavement alternatives. But in the mean time, further comments can be made on the economical implications of each. For instance, the findings of Grameen Sampark (200?) justify that the initial cost of concrete pavement is 28 % higher over that of the flexible counterpart. But putting the Life Cycle Cost (see Section 2.5.2) in mind, we may observe 19 % less cost in reverse. Apart from Life Cycle Cost Analysis (LCCA), there are scenarios that definitely necessitate rigid pavements without any doubt like: locations with water logged/ areas of heavy rainfall, subgrade of lower CBR value, sites in which cement and fly ash are in close proximity, heavy trafficked segments, curved portions & heavy gradients of a roadway section, etc. These cases greatly discourage choosing flexible pavements. [3] Additionally, as the research of Atakilti G. Bezabih & Satish Chandra (2009) showed, flexible pavements exhibit wider range of variation in cost with respect to design parameters of traffic and soil CBR but the overall variation in cost of rigid pavements is comparatively small. The design of a rigid pavement is highly influenced by the occurrence of a small number of heavy axle loads while its fatigue life is prone to small changes in the stress ratio which can happen with a small increase of the loading along the axle load axis. In the above cited research, it was observed that flexible pavements are more economical for low volumes of traffic whereas rigid pavements are economical for higher volumes. For intermediate cases, both appear to be good competitors.[4] Furthermore, several researches conducted in the area of approving long life cement concrete pavements have actually shown that rigid pavements encompass considerable advantages over their flexible counterparts. As of Wouter Gulden (2009), informed approach towards selecting features such as: subgrade, dowels, treated or stabilized subbase, tiebars, joint sealant, joint spacing etc can, to our surprise, make rigid pavements more economical in terms of initial investment. [5]
1.2 Statement of the Problem Transportation is crucial for a nation’s development and growth. And in a developing country like ours, the transportation infrastructure has undeniable contribution to the welfare of the public and private sectors. However, the road infrastructure of Ethiopia has been characterized by nothing except insufficiency and unacceptable quality. This has recently necessitated a desperate means to come up with a well developed road transport sector in order to fuel up the growth process of the nation. In Ethiopia, road transport is apparently the most dominant mode and accounts for 90 to 95 percent of motorized inter urban freight and passenger movements. However, because of its limited road network, the provision of transportation means remains one of the formidable challenges for Ethiopia in its endeavor towards socio-economic development and poverty reduction. [6] The current standard and condition of the road network is a constraint to the development of an efficient road transport system. This is being addressed through major road building 5 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
and rehabilitation projects by the title Road Sector Development Program (RSDP). Unfortunately, this pace of change can lead to other road transport problems if action is not taken now on new enforceable laws and resources to implement them. [7] The Road Sector Development Plan (RSDP) was formulated in three phases to address the constraints related to restricted road network coverage and low standards. The first phase of RSDP (1997 – 2002) focused on the rehabilitation of the road network to an acceptable condition. Specifically, the program put emphasis on (1) rehabilitation of main roads; (2) upgrading main roads; (3) construction of new roads; and (4) regular maintenance on the network. Side by side, the program also considered major policy and institutional reforms. The second phase (2002 – 2007) was signified by its encouraging outcomes with a total disbursement rate of 125 % and 73 % investment on federal and regional roads respectively. Within the ten-year period of the program, the total estimated expenditure amounted to 25.4 billion Birr (US$ 2.9 billion). [6] The last phase being shortest among the three (2007 – 2010) saw the construction of additional road ways. By the end of 2010, a total of 39965 km long roads were finalized as a result of the thirteen-year RSDP. By the end of the three-phase RSDP, the RSDP IV was prepared as part of the Government’s overall Growth and Transformation Plan (GTP). This is a major strategic pillar of the GTP consisting of: Rehabilitation of 728Km of trunk roads, Upgrading of 5,023 Km of trunk and link roads, Construction of 4,331 Km of new link roads, Heavy maintenance of 4,700 Km of paved and gravel roads and Routine maintenance of 84,649 Km of road network. The program also consists of the construction of new rural roads through the Rural Road Authorities (RRAs); and Construction of Woreda roads through the Woreda road offices. The total cost estimate for implementing RSDP IV happens to be 125.277 billion ETB. However, a staggering 60 to 75 percent of this budget has been scheduled to be expended on maintenance and upgrading of the existing roadway network. This signifies an even greater amount of maintenance cost let alone the initial investment needed to construct new flexible road pavements. Rigid pavements are popularly opposed by many for a couple of associated setbacks, i.e. more initial investment compared to their flexible counterparts and difficulty of repair in cases of wrong design. Despite these factors, rigid pavements have their own irresistibly strong set of advantages such as: prolonged design life, less maintenance, early completion of construction, reduced fuel consumption etc…. But on the contrary, with shorter design period like 20 years, flexible pavements (especially on large nationwide cases) call for ridiculously expensive maintenance and rehabilitation operations as the RSDP IV is a living witness. This scenario leads us to the question why alternative pavement construction techniques cannot be explored. The manipulation of knowledge led road construction along with adoption of rigid pavements serve as an alternative to flexible pavements. Its economical analysis yields precise results when thinking of long term (30 to 60 years) conditions on matters related to maintenance and upgrading. Furthermore, as mentioned in Section 1.1, it could also be economical in terms of initial investment provided that we work on selecting appropriate features. [5] In addition to this, direct and indirect advantages may be mentioned with regards to performance and foreign currency saving (expended on bituminous binders).
6 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
However, this paper is not advocating the use of rigid pavements on all road networks. Circumstances that will suit flexible pavements will always continue to exist. To ascertain the implications of rigid pavement employment as an alternative to flexible pavements in Ethiopian Road Construction, this research picked a segment that is among the most trafficked corners of the nation’s road network for analysis, i.e. ‘Adama’ (Nazareth) to ‘Awash’. And in addition to intense traffic, other reasons of selection include: the occurrence of heavy accidents due to surface conditions, different considerable road surface failures, poor subgrade conditions in some points along the alignment (Black Cotton), ground water conditions (especially around Lake ‘Beseka’), its geological formation, the environment etc.
1.3 Objectives and Scope of the Study In order to ease the transition from flexible to rigid pavement, it is appropriate to make researches in seeking the potential prospects. However, studying Rigid Pavements to the required level and depth will consume considerable resource and time. Therefore, for this research purpose, we have limited the case study to a certain alignment to conquer the set of outlined objectives. The title of this thesis is “The Design of a Roadway Section from Adama to Awash using Rigid Pavement and Its Implication in Ethiopian Road Construction”. As an end goal, we will try to come up with suitable conditions of preference. In the meantime, the project will dedicate a great portion to the design and economic analysis of rigid pavements. Last but not least, the thesis will be accompanied by a demonstrative design program using the LISP Programming Software. Unless stated otherwise, the analysis, design and detailing will be strictly carried out using the AASHTO Guide for Design of Pavement Structures, 1993, Volume I. The general objectives aim to tell about the significance of the study to the nation’s overall practice and the specifics focus on those findings and conclusions regarding the segment picked and analyzed. Generally speaking, the following are the major objectives that are set to be met by the completion of this thesis: To demonstrate the feasibility of rigid pavement construction in Ethiopia. To assess the conditions and areas of suitability that proves rigid pavements to be more economical over flexible pavements. To optimize design options with regards to thickness, mix proportions and base layer types from different concrete pavement options. To build demonstrative design templates, design catalogs and a computer program.
7 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
References TO CHAPTER ONE [1]
Garber, Nicholas J. & Hoel, Lester A. (2009), Traffic and Highway Engineering, 4th Edition, Cengage Learning Toronto, Canada, (Pp. 551 - 553)
[2]
Rogers, Martin (2003), Highway Engineering, Blackwell Publishing Ltd, Dublin Institute of Technology – Ireland (Pp. 192 – 194)
[3]
Sampark, Grameen (200?), Cement Concrete Roads Vs Bituminous Roads – Cost Analysis, Cement Manufacturer’s Association, India (Pp. 1 – 4)
[4]
Bezabih, Atakilti G. & Chandra, Satish (2009), Comparative Study of Flexible and Rigid Pavements for Different Soil and Traffic Conditions, Journal of the Indian Roads Congress – Paper No. 554, India (Pp. 1 – 6)
[5]
Gulden P.E., Wouter (2009), Designing PCC Pavement for Economy and Longevity, American Concrete Pavement Association – Southeast Chapter, Atlanta, Georgia (Pp. 48 – 50 & 121)
[6]
Worku, Ibrahim (2011), Road Sector Development and Economic Growth in Ethiopia, EDRI Working Paper 4, Addis Ababa, Ethiopia: Ethiopian Development Research Institute (Pp. 9 – 12)
[7]
AACC & Sectoral Associations (2009), The Management of Commercial Road Transport in Ethiopia, Addis Ababa Chamber of Commerce – Private Sector Development Hub, Addis Ababa, Ethiopia (Pp. 16 – 18)
8 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
CHAPTER TWO LITERATURE REVIEW 2.1 Introduction The development of design methods for rigid pavements is not as dramatic as that of flexible pavements because the flexural stress of concrete has long been considered as a major, if not the only, design factor. It has evolved through three major stages of development in the past century only and these are: Analytical Solutions, Numerical Methods and Other Miscellaneous Developments. The Analytical Solutions range from simple closed form formulae to complex derivations for determining the stresses and deflections in concrete pavements. Different people have contributed a lot and among them, Goldbeck (1919) developed a simple equation for the design of rigid pavements while Westergaard (1926 – 1948), based on Liquid Foundations, developed equations relevant to temperature curling as well as three cases of loading: load applied near the corner, near the edge and at the interior of a large slab. Apparently, the works of Pickett et al. (1951), by assuming Solid Foundations, implied theoretical solutions for cement concrete slabs on an elastic half space. The complexities of the mathematics in Analytical Solutions and the assumption that the slab and the subgrade are in full contact necessitated Numerical Solutions. It is well known that due to pumping, temperature curling and moisture warping, the slab and subgrade are usually not in contact. With the advent of computers and numerical methods, some analyses based on partial contact were developed. Hudson and Matlock (1966) applied the discrete element method (similar to the finite difference method) by assuming the subgrade to be a dense liquid and the slab is seen as an assembly of elastic joints, rigid bars and torsion bars. Later on the method was extended by Saxena (1973) towards Finite Element Method in order to analyze slabs on an elastic solid foundation. [1] Even though Other Developments have their own theoretical methods which are helpful in improving and extrapolating design procedures, pavement performance is of paramount importance. This resulted present day design methods to be supplemented with probabilistic approaches and dynamic analyses for better performance of Rigid Pavement. For instance, Fatigue of Concrete and Pumping, caused by traffic and environmental factors respectively, are the two major areas of concern affecting performance. As of J. Silverio Larralde (1985), pumping causes premature failure while fatigue promotes long term deterioration. [2] According to Darestani et al(2006), investigation of the recorded time history responses of test sections undertaken indicates the importance of dynamic analysis 9 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
in pavement design. Results also indicate that dowel position can strongly influence pavement responses. [3] In addition, for better performance under fatigue loading, the results of Suresh Kumar et al (2012) implied the employment of high performance cement concrete of appropriate mix proportion to be a good contribution. [4] The application of probabilistic concepts to rigid pavement design was initially presented by Kher & Darter (1973), and the concepts were incorporated into the AASHTO design guide (AASHTO, 1986). For the purpose of this research, we have put emphasis on the design concepts and numerical solutions employed in AASHTO Design Guide, 1993. Accordingly, the design of rigid pavement structures needs to take into account different considerations and requirements to ascertain design procedures that potentially lead to the required design parameters. To do so, one is likely to handle several factors at the initial stage to come up with a more realistic analysis and design. In the mean time, all of the factors to be considered may not be significant in proportioning slab thickness, reinforcement and slab dimensions but rather give some information on performance criterion, cost and durability of the designed system. Therefore, we say certain design considerations, in addition to other requirements, will be used for obtaining the required design parameters. We call these design requirements. Many design manuals, more or less, reflect similarity with regard to the above cases. As per the listing of AASHTO, Guide for Design of Pavement Structures, 1993, the design considerations to be taken are: pavement performance, traffic, roadbed soil, materials of construction, environment, drainage, reliability, life-cycle costs, and shoulder design. Of these, pavement performance, environment, reliability, drainage, material of construction and traffic are coupled with others such as reinforcement variables and time constraints to constitute design requirements. These design requirements are investigated to yield appropriate design parameters by following a certain set of procedures. [5]
2.2 Design Considerations AASHTO (1993) includes the design considerations listed above in its method of design and Equation (2.1) is generally used for the design of rigid pavements. ∆PSI ] 4.5-1.5 log 10 (W18 )= ZR x So + 7.35 x log10 (D+1)- 0.06 + + 1.624 x 107 1+ (D+1)8.46 log10 [
Sc' x Cd x (D0.75 - 1.132)
(4.22 - 0.32 x pt ) x log10
215.63x J x [D0.75[
. . . . . . (2.1)
18.42 ] Ec 0.25 ( ) ] k 10
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Where: W18 = Predicted number of 18 kip equivalent single axle load applications, ZR = Standard normal deviate, So = Combined standard error of the traffic and performance prediction, D = Thickness (inches) of pavement slab, ΔPSI = Difference between the design serviceability indexes, (initial & terminal) S’C = Modulus of rupture in psi for Portland Cement Concrete used on specific, J = Load transfer coefficient to adjust load transfer characteristics, Cd = Drainage coefficient, Ec = Modulus of elasticity (psi) for Portland cement concrete, and K = Modulus of subgrade reaction (pci).
2.2.1 Pavement Performance It includes some considerations of functional performance, structural performance and safety. One important aspect of safety is the frictional resistance provided at the pavementtire interface. The structural performance is related to its physical condition; i.e., occurrence of cracking, faulting, raveling, or other conditions which would adversely affect the load carrying capability of the pavement structure or would require maintenance. And the functional performance of a pavement concerns how well the pavement serves the user. In this context, riding comfort or ride quality is dominant. The serviceability of a pavement is expressed in terms of the present serviceability index (PSI). The PSI is obtained from measurements of roughness and distress, e.g., cracking, patching etc, at a particular time during the service life of the pavement. Roughness is the dominant factor in estimating the PSI of a pavement. Thus, a reliable method for measuring roughness is important in monitoring the performance history of pavements. The scale for PSI ranges from 0 through 5, with a value of 5 representing the highest index of serviceability. For design it is necessary to select both an initial and terminal serviceability index. The initial serviceability index (po) is an estimate by the user of what the PSI will be immediately after construction. Values of po established for AASHO Road Test conditions were 4.2 for flexible pavements and 4.5 for rigid pavements. The terminal serviceability index (pt) is the lowest acceptable level before resurfacing or reconstruction becomes necessary for the particular class of highway. An index of 2.5 or 3.0 is often suggested for use in the design of major highways, and 2.0 for highways with a lower classification. For relatively minor highways, where economic considerations dictate that initial expenditures needs to be kept low, at pt of 1.5 may be used. Expenditures may also be minimized by reducing the performance period. Such a low value of pt should only be used in special cases. The major factors influencing the loss of serviceability are traffic, age, and environment. Equation (2.2) gives total loss of serviceability taking into account traffic and environment along a certain design life. ΔPSI = ΔPSI Traffic + ΔPSI Swell/Frost Heave . . . . . . . . . (2.2) 11 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Where: ΔPSI = total loss of serviceability, ΔPSI Traffic = loss due to traffic (ESAL's), and ΔPSI Swell/frost heave = loss due to swelling and/or frost heave of roadbed soil. It can be noted that the effect of swelling soils or frost heave is to reduce the predicted service life of the pavement. And it is not recommended to increase pavement structural thickness to offset the serviceability loss due to swelling soils; but it is feasible, however, to control frost heave by increasing the thickness of non frost susceptible material. In many swelling situations, it may be possible to reduce the effect of swelling soil by stabilization of the expansive soil or by replacement of these soils with non expansive material. When experience indicates this is a viable procedure, it is not necessary to estimate the effect of swelling soil on the life cycle. [5]
2.2.2 Traffic Traffic information required by the design equation includes axle loads, axle configuration, and number of applications. The results of the AASHO Road Test have shown that the damaging effect of the passage of an axle of any load can be represented by a number of 18 kip equivalent single axle loads or ESAL's. The determination of design ESAL's is a very important consideration for the design of pavement structures. 2.2.2.1 Evaluation of Traffic There are four key considerations which influence the accuracy of traffic estimates and which can significantly influence the life cycle of a pavement: the correctness of the load equivalency values used to estimate the relative damage induced by axle loads of different mass and configurations, the accuracy of traffic volume and weight information used to represent the actual loading projections, the prediction of ESAL's over the design period, and the interaction of age and traffic as it affects changes in PSI. The ESAL's for the performance period represent the cumulative number from the time the roadway is opened to traffic to that when it is reduced to a terminal value, pt equal to 2.5 or 2.0. If the traffic is underestimated, the actual time to pt will probably be less than the predicted performance period, thereby resulting in increased maintenance and rehabilitation costs. Performance period and corresponding design traffic should reflect real life experience. The performance period should not be confused with pavement life. The pavement life may be extended by periodic rehabilitation of the surface or pavement structure. The load equivalency factor increases approximately as a function of the ratio of any given axle load to the standard 18 kip single axle load raised to the fourth power. This relationship will vary depending on the structural number and terminal serviceability; however, it is generally indicative of load effects. Thus, it is important to obtain reliable truck weight information for class and especially for multi axle trucks since these vehicles will constitute a high percentage of the total ESAL's on most projects. [5] 12 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
2.2.2.2 Design Traffic Loading The method for computing Cumulative Equivalent Axle Load over the design life is described in ERA (Pavement Design Manual 2002, Volume II). The same method is used for rigid pavement but the equivalency factors to be used are those given in Table 2.1. Table 2.1: Equivalency Factors for Axle Loads, Rigid Pavements (Source: ERA Manual) Wheel Load (103 kg) (Single & Dual)
Axle Load (103 kg)
Equivalency Factor
1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0
3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0 20.0
0.02 0.05 0.13 0.28 0.53 0.93 1.53 2.40 3.63 5.25 7.33 9.92 13.1 17.0 21.6 27.1 33.7 41.4
These factors are marginally higher when compared with the corresponding values from ERA Pavement Design Manual, Volume I (2002), for loads up to the standard axle load. However, for heavier loads, the equivalency factors for rigid pavements are lower and the difference increases exponentially. This reflects the fact that rigid pavements are more resistant to heavy loads since they spread loads over a large surface of sub-base. [6]
2.2.3 Roadbed Soil The definitive material property mostly used to characterize roadbed soil for pavement design is the resilient modulus (MR). The resilient modulus is a measure of the elastic property of soil recognizing certain nonlinear characteristics. The resilient modulus can be used directly for the design of flexible pavements but must be converted to subgrade reaction modulus (k-value) for the design of rigid pavements. Direct measurement of subgrade reaction can be made if such procedures are considered preferable.[5] Heukelom and Klomp (Corps of Engineers) have reported correlations between the CBR value, using dynamic compaction, and the in situ soil modulus. It is given by: MR (psi)= 1500 X CBR . . . . . . . . . . . . . (2.3)
13 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Similarly, a relationship developed by The Asphalt Institute which relates R-value (Reliability (see section 2.3.1.3)) to MR is: MR (psi) = A + B x (R value) . . . . . . . . . (2.4) Where: A =772 to 1,155 and B = 369 to 555. The following correlation may be used for fine-grained soils (R value less than or equal to 20) until designers develop their own approach: MR = 1,000 + 555 x (R value). . . . . . . . . (2.5)
2.2.4 Materials of Construction Rigid pavements generally consist of a prepared roadbed underlying a layer of sub base and a pavement slab. The sub-base may be stabilized or unstabilized. In cases of low volume road design where truck traffic is low, a sub-base layer may not be necessary between the prepared roadbed and the pavement slab. A drainage layer can be included in rigid pavements in much the same manner described for, flexible pavements. [5] 2.2.4.1 Sub-base It consists of one or more compacted layers of selected material placed between the subgrade and the rigid slab for the following purposes: to provide uniform, stable, and permanent support, to increase the modulus of subgrade reaction (k), to minimize the damaging effects of frost action, to prevent pumping of fine-grained soils at joints, cracks, and edges of the rigid slab, and to provide a working platform for construction equipment. 2.2.4.2 Pavement Slab The basic materials in the pavement slab are Portland cement concrete, reinforcing steel, load transfer devices, and joint sealing materials that should conform to specifications. i. Portland Cement Concrete Under the given specific conditions, the minimum cement factor should be determined on the basis of laboratory tests and prior experience of strength and durability. Air entrained concrete should be used whenever it is necessary to provide resistance to surface deterioration from freezing and thawing or from salt or to improve the workability. ii. Reinforcing Steel The reinforcing steel used in the slab should have surface deformations adequate to bond and develop the working stresses in the steel. For smooth wire mesh, this bond is developed through the welded cross wires. For deformed wire fabric, the bond is developed by deformations on the wire and at the welded intersections. The reinforcing steel will be placed at a depth of ¼ h+ 1 inch from the surface of the reinforced slab. This will place the steel above the neutral axis of the slab and will allow clearance for dowel bars. The wire or bar sizes and spacing should be selected to give, as nearly as possible, the required percentage of steel per foot of pavement width or length. 14 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Two layers of wire fabric or bar mat, one placed directly on top of the other, may be used to obtain the required percent of steel; however, this should only be done when it is impracticable to provide the required steel in one layer. The layers must be fastened together (wired or clipped) to prevent excessive separation during concrete placement. When the reinforcement is installed and concrete is to be placed through the mat or fabric, minimum clear spacing between bars will be 1½ times the maximum aggregate size.[5] As of J. Paul Guyer (2009), deformed bars will be overlapped for at least 24 bar diameters measured from the tip of one bar to the tip of the other bar. The lapped bars will be wired or otherwise securely fastened to prevent separation during concrete placement. Wire fabric will be overlapped for a distance equal at least one spacing of the wire in the fabric or 32 wire diameters, whichever is greater. The length of lap is measured from the tip of one wire to the tip of the other wire normal to the lap. The wires in the lap will be wired or otherwise securely fastened to prevent separation during concrete placement. [7] iii. Joint Sealing Materials Three basic types of sealants are presently used for sealing joints: Liquid sealants include a wide variety of materials including: asphalt, hot poured rubber, elastomeric compounds, silicone, and polymers. The materials are placed in the joint in a liquid form and allowed to set. Preformed elastomeric seals, which are extruded neoprene seals having internal webs that exert an outward force against the joint face. The size and installation width depend on the amount of movement expected at the joint. The last group of sealants is known as Cork expansion joint fillers, which are of two types (standard expansion joint filler and self expanding (SE) type). iv. Longitudinal Joints Longitudinal joints are needed to form cracks at the desired location so that they may be adequately sealed. They may be keyed, butted, or tied joints, or combinations thereof. They should be sawed or formed to a minimum depth of one fourth of the slab thickness. Timing of the saw cutting is critical to the crack formation at the desired location. The maximum recommended longitudinal joint spacing is 16 feet (4.87m). v. Load-Transfer Devices Mechanical load transfer devices for transverse joints should possess the following attributes: they should be simple in design, be practical to install, and permit complete encasement by the concrete and they should properly distribute the load stresses without overstressing the concrete at its contact with the device. They should offer little restraint to longitudinal movement of the joint and they should be mechanically stable under the wheel load weights and frequencies that will prevail in practice. They should also be resistant to corrosion. A commonly used load transfer device is the plain, round steel dowel. Although round dowels are the most commonly used, other mechanical devices that have proven 15 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
satisfactory in field installations may also be used. Consideration may also be given to omitting load transfer devices from transverse weakened plane joints in plain jointed concrete pavement when supported on a treated permeable base. [5] vi. Tie Bars Tie bars are designed to withstand the maximum tensile forces required to overcome subgrade drag. They are not designed to act as load transfer devices.
2.2.5 Environment Two main factors are considered with regard to pavement performance and design. These are temperature and rainfall. Temperature will affect contraction and expansion of Portland cement concrete, and freezing and thawing of the roadbed soil. And in combination, temperature and moisture differential between the top and bottom of concrete slabs in jointed concrete pavements creates an upward curling and warping of the slab ends that result in pumping and structural deterioration of undrained sections. The climatic factors of air temperature, solar radiation received at the surface, wind, and precipitation are major parameters that affect the severity of frost effects in a given geographical area. The first three mainly affect the temperature regime in the pavement structure, including the important parameters of depth of frost penetration, number of freeze-thaw cycles, and duration of the freezing and thawing periods. Precipitation affects mainly the moisture regime but causes changes in the thermal properties of the soil and interacts with the other climatic variables determining ground temperatures as well. [5]
2.2.6 Drainage Drainage of water from pavements has always been an important consideration in road design; however, current methods of design have often resulted in base courses that do not drain well. Generally, water enters the pavement structure in many ways and effects of this water (when trapped within the pavement structure) include: reduced strength of unbounded granular materials, reduced strength of roadbed soils, pumping of concrete pavements with subsequent faulting, cracking, and general shoulder deterioration. For design purposes, drainage effects are directly considered in terms of the effect of moisture on subgrade strength (by reducing the modulus) and on base erodibility of concrete pavements. And the methods for treating water in pavements generally consisted of: preventing water from entering, providing drainage to remove excess water, and building the pavement strong enough to resist the combined effect of load and water. [5]
2.2.7 Shoulder Design As defined by AASHTO (1993), a highway shoulder is the “portion of roadways contiguous with the travel way for accommodation of stopped vehicles for emergency use, and for lateral support of base and sub-base courses.” It is also considered by some agencies as a temporary detour to be used during rehabilitation of the usual travel way. 16 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
No specific design criteria are provided in AASHTO (1993) for the determination of the pavement structure for shoulders but different agencies developed specific design criteria for shoulders. The use of tied shoulders or a widened width of paving in the lane adjacent to the shoulder has proven to be beneficial to overall performance of rigid pavements. [5]
2.3 Design Requirements 2.3.1 Design Variables In the determination of design parameters with in a pavement structure, on which a rigid concrete slab is laid at top; there are different ever changing preconditions governing a certain design called variables. That is, the set of criteria which must be considered for each type of road surface design procedure. And as per the AASHTO (1993), set of criteria or so called design variables like; Time Constraints (Performance and Analysis Period), Traffic, Reliability and Environmental Impacts (Roadbed Swelling and Frost Heave) are the major ones which must be put under consideration. [5] While coming to ERA manual (2002), some of the factors which shall intervene in the design of rigid pavements are: The sub grade quality, the quality of the steel and concrete composing the slabs, the traffic, the environment (moisture and temperature) and the notional design life. [6] And what is different here is that, reliability in AASHTO guide is given a specific notion in ERA manual to be related to the quality with regard to concrete and steel in addition to the sub grade characteristics. And later in this research, we may justify which ones are the critical variables in the design procedures to follow. Apart from the ordinary design procedures specified by the AASHTO design guide and ERA manual, additional variables have their room in design concepts. For example, as the research by Daniel Paul Franta (2012) pointed out, temperature, time of year, weather during construction, mix design, slab thickness and slab dimensions, affect the shape of a slab and the surface of a profile. [8] Different design scenarios may require different variables for computation of relevant parameters. But we only consider the AASHTO (1993) design variables for discussion which are carried out here under and some are as follows: 2.3.1.1 Time Constraints The characteristics and durability of rigid pavement structures greatly depend on the design life. [9, 10] In fact, design life dictates decisions made on the selection of different parameters. Due to such and other relevant reasons, we may infer the notional design life to be categorized as time constraint according to AASHTO (1993). These variables involve the selection of performance and analysis period inputs which affect (or constrain) pavement design from the perspective of time. Consideration of these constraints is required for the design of both highways and low-volume roads. These also permit the designer to select one strategy among many. These strategies range from
17 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
allowing the initial structure to last the entire analysis period (i.e. performance period equals analysis period) to stage construction with planned maintenance and overlays. [5] Some points to consider before deciding design life include functional importance of the road, traffic volume, location and terrain of the project, financial constraint anddifficulty in forecasting traffic. i. Performance Period This refers to the period of time that an initial pavement structure will last before it needs rehabilitation. It also refers to the performance time between rehabilitation operations. According to AASHTO (1993), the performance period is equivalent to the time elapsed as a new, reconstructed, or rehabilitated structure deteriorates from its initial serviceability to its terminal serviceability. It shall be noted that, in actual practice, the performance period can be significantly affected by the type and level of maintenance undertaken. The minimum performance period is the shortest duration of time a given stage should last and the maximum practical duration of time that the user can expect from a given stage. This limiting time period may be the result of Present Serviceability Index (PSI) loss due to environmental factors, disintegration of surface, etc. The selection of longer time periods than can be achieved in the field will result in unrealistic designs. Thus, if lifecycle costs are to be considered accurately, it is important to give some consideration to the maximum practical performance period of a given pavement type. [5] ii. Analysis Period As the report of Portland Cement Association, PCA (1995) indicates, analysis period is sometimes mentioned to be design period rather than saying it is synonymous to pavement life in which the later is of no precise definition. [11] But generally speaking, it is the period of time for which the analysis is to be conducted or the duration any design strategy must cover. Because of the consideration of the maximum performance period, it may be necessary to consider and plan for stage construction (i.e., an initial pavement structure followed by one or more rehabilitation operations) to achieve the desired analysis period. And according to AASHTO (1993), it is recommended that consideration be given to longer analysis periods since these may be better suited for the evaluation of alternative long-term strategies based on life-cycle costs. The manual also recommends the inclusion of at least one rehabilitation process. For high-volume urban freeways, longer analysis periods may be considered. [5] Table 2.2 serves as a general guideline.
18 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 2.2: Guide lines for Analysis Period (Source: AASHTO Guide, 1993) Highway Conditions
Analysis Period (Years)
High Volume Urban
30 to 50
High Volume Rural
20 to 50
Low Volume Paved
15 to 25
Low Volume Aggregate Surface
10 to 20
2.3.1.2Traffic Determining traffic flow or volume is an essential part of pavement design. To do so, three basic variables can be introduced for analysis as per Highway Capacity Manual (2000). They are: volume or flow rate, speed, and density which can be used to describe traffic on any roadway. And of the three, volume or traffic flow is common to both uninterrupted and interrupted flow facilities, but speed and density apply primarily to uninterrupted flow. Some parameters related to flow rate, such as spacing and headway are also used for both types of facilities while others, such as saturation flow or gap are specific to interrupted flow. Coming to its significance in the design of highways, we may discuss multilane highways (urban segments) and two lane highways (rural segments) separately. Studies of the flow characteristics of multilane highways have defined base conditions for developing flow relationships and adjustments to speed. The base conditions for multilane highways consist of: minimum lane widths, minimum total lateral clearance (along the edge and in the median), only passenger cars in the traffic stream, no direct access points along the roadway, division of road way and free flow speed (FFS). These base conditions represent the highest operating level of multilane rural and suburban highways. But when we analyze two lane highways or rural segments, which is our scenario (from ‘Awash’ to ‘Adama’), we need only traffic data, i.e. the two way hourly volume, a peakhour factor (PHF), and the directional distribution of traffic flow. The PHF may be computed from field data or approximate values from manuals may be adopted. Traffic data also include the proportion of trucks and recreational vehicles (RVs) in the traffic stream. [12] As per AASHTO (1993), the design procedures for both highways and low volume roads are all based on cumulative expected 18 kip (80.07 KN) equivalent single axle loads (ESAL) during the analysis period. To do so, the mixed traffic shall be converted into these ESAL units. This is because for any design situation in which the initial pavement structure is expected to last (the analysis period without any rehabilitation or resurfacing) all that is required from traffic data is the total number of equivalent single axles over the analysis period. If, however, stage construction is considered and rehabilitation or resurfacing is 19 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
anticipated, then it is essential to prepare a graph of cumulative ESAL traffic versus time. This will be used to separate the cumulative traffic into the periods during which it is encountered. [5] Equation (2.6) can be used to forecast the traffic to a time t, knowing the growth rate g and cum. ESAL at t = 0 (W18 (to)):
W18 (t) =W18 (to ) [
(1+g)t - 1 g
]. . . . . . . . . . . (2.6)
The predicted traffic is generally the cumulative ESAL expected on the highway, whereas the designer requires the axle applications in the design lane. Thus, unless specifically furnished, it is possible to factor the design traffic by direction and then by lanes (if more than two). Equation (2.7) is used to determine the traffic (W18) in the design lane: W18 =DD x DL x Ŵ18 . . . . . . . . . . . (2.7) Where: DD = a directional distribution factor, expressed as a ratio, that accounts for the distribution of ESAL units by direction, DL = a lane distribution factor, expressed as a ratio, that accounts for distribution of traffic when two or more lanes are available in one direction, and Ŵ18 = the cumulative two directional ESAL units predicted for a specific section of highway during the analysis period. Although the directional distribution factor is generally 50 percent for most roadways, there are instances where more weight may be moving in one direction than the other. Thus, the side with heavier vehicles should be designed for a greater number of ESAL units. As AASHTO (1993) further justifies, DD may vary from 0.3 to 0.7, depending on which direction is loaded and which is unloaded.[5] For the lane distribution factor (DL), the Table 2.3 can be used as a guide when ever exact count is not found (which is the usual case). Table 2.3: Guide lines for Lane Distribution Factor, DL (Source: AASHTO Guide, 1993) Number of Lanes in each Direction
Percent of ESAL in Design Lane
1
100
2
80 to 100
3
60 to 80
4
50 to 75
2.3.1.3 Reliability As per the definition of AASHTO (1993), the reliability of a pavement is the probability that a pavement section will perform satisfactorily over the traffic and environmental 20 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
conditions for the design period. Basically, it is a means of incorporating some degree of certainty into the design process to ensure that the various design alternatives will last the analysis period. It can be well defined in two cases. Firstly, when we are thinking of designed pavement sections and secondly, when we are considering pavement condition, accumulated axle loads, and pavement performance variables. [5] i. Designed Pavement Section For the purpose of this discussion, a designed pavement section is defined to be a section that is designed through the use of a specific design equation. The equation is assumed to be an explicit mathematical formula for predicting the number of ESAL that the section can withstand (Wt) before it reaches a specified terminal level of serviceability (pt). Predictor variables or design factors in the equation can be put in one or another of four categories: Pavement structure factors (PSF), Roadbed soil factors (RSF), Resilient modulus, climate related factors (CRF), and Pavement condition factors (PCF). The design equation may be written in the form: 𝑾𝒕 = 𝒇(𝐏𝐒𝐅, 𝐑𝐒𝐅, 𝐂𝐑𝐅, 𝐏𝐂𝐅) . . . . . . . . . . (2.8) The utilization of Equation 2.8 to arrive at a structural design involves additional steps. That is: use of relevant traffic and load meter data, and specified equivalence factors to predict the total number of ESAL's, wT, that the section will handle over the design period of T years, and multiplication of the traffic prediction, wT, by a reliability design factor, FR, that is greater than or equal to one, and substitution of FR x wT for Wt, in Equation (2.8).[5] 𝑾𝒕 = 𝑭𝑹 𝒙 𝒘𝑻= 𝒇(𝐏𝐒𝐅, 𝐑𝐒𝐅, 𝐂𝐑𝐅, 𝐏𝐂𝐅) . . . . . . . . . . (2.9) ii. Definition of Reliability In this case, we define three types of variables that are essential to the definition of reliability. The variables represent pavement condition, axle load accumulations, and pavement performance. The discussion includes variables that were necessarily introduced previously so that the designed pavement section could be completely defined. Clarifying the significance of the above two cases, the reliability design factor accounts for chance variations in both traffic prediction (w18) and the performance prediction (W18), and therefore provides a predetermined level of assurance (R) that pavement sections will survive the period for which they were designed. Generally, as the volume of traffic, difficulty of diverting traffic, and public expectation of availability increases, the risk of not performing to expectations must be minimized. This is accomplished by selecting higher levels of reliability. [5] Table 2.4 presents recommended levels of reliability for various functional classifications. It is also to be noted that the higher levels correspond to the facilities which are supposed to provide greater service, while the lowest level, 50 percent, corresponds to local roads. 21 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 2.4: Suggested Levels of Reliability for Various Functional Classifications (Source: AASHTO Guide, 1993) Functional Classification
Recommended Level of Reliability Urban
Rural
Interstate and Other Freeways
85 to 99.9
80 to 99.9
Principal Arterials
80 to 99
75 to 95
Collectors
80 to 95
75 to 95
Local
50 to 80
50 to 80
As explained earlier, design performance reliability is controlled through the use of a reliability factor (FR) that is multiplied by the design period traffic prediction (w18) to produce design applications (W18) for the design equation. For a given reliability level (R), the reliability factor is a function of the overall standard deviation (So) that accounts for both chance variation in the traffic prediction and normal variation in pavement performance prediction for a given w18. [5] Rather than assuming conservative values, the designer should use his best estimate of the mean or average value for each input value. The selected level of reliability and overall standard deviation will account for the combined effect of all variation in design variables. Application of the reliability concept requires the following three steps. That is: defining the functional classification of the facility (rural or urban condition), selecting a reliability level from the range given in Table 2.4 and finally, a standard deviation (So) selected which is representative of local conditions should be picked. Total standard deviations of 0.35 and 0.45 for rigid and flexible pavements respectively were the results of AASHO Road Test after correction for traffic error. [5] 2.3.1.4 Environmental Impacts The environment can affect pavement performance in several ways. Temperature and moisture changes can have effect on the strength, durability and load carrying capacity of pavement and road bed materials. On the other hand, major impacts like roadbed swelling, pavement blowups, frost heave, disintegration, etc., have effects on loss of riding quality and serviceability. Again, aging, drying and overall material deterioration due to weathering are considered in terms of their inherent influence on pavement performance prediction models. The actual treatment of the effects of seasonal temperature and moisture changes on material properties are considered as part of economic analysis in concrete pavement type selection. But for design purposes, necessary criteria for quantifying the input requirements are roadbed swelling and frost heave. If either of these can lead to a significant loss in serviceability or ride quality during the analysis period, then it (they) should be considered 22 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
in the design analysis for all pavement structural types except perhaps aggregate surfaced roads. If serviceability based models are developed for factors like pavement blowups, then they may be taken as supplements to the design procedure. To account for the effect of environmental variables on pavement performance, we shall produce a graph of serviceability loss versus time, i.e. the serviceability loss due to environment (swelling and frost heave) must be added to that resulting from cumulative axle loads. [5]
2.3.2 Performance Criteria 2.3.2.1 Serviceability The serviceability of a pavement is defined as its ability to serve the type of traffic which uses it with the primary measure being the Present Serviceability Index (PSI). PSI ranges from 0 (impossible road) to 5 (perfect road). So we shall provide a means of designing a pavement based on a specific total traffic volume and a minimum level of serviceability desired at the end of the performance period. Selection of the lowest allowable PSI or terminal serviceability index (pt) is based on the lowest index that will be tolerated before rehabilitation, resurfacing, or reconstruction becomes necessary. An index of 2.5 or higher is suggested for design of major highways and 2.0 for highways with lesser traffic volumes. [5] One criterion for identifying a minimum level of serviceability may be established on the basis of public acceptance, Table 2.5. Table 2.5: General Guidelines for minimum levels of pt(Source: AASHTO, 1993) Terminal Serviceability Level 3.0 2.5 2.0
Percent of People Stating Unacceptable 12 55 85
For relatively minor highways where initial capital is traditionally kept at a minimum, it is suggested that acceptability be accomplished by reducing the design period or the total traffic volume rather than by designing for a terminal serviceability less than 2.0. Since the time at which a given pavement structure reaches its terminal serviceability depends on traffic volume and the original serviceability (po), some consideration must also be given to the selection of po.[5] The po values observed at the AASHO Road Test were 4.2 for flexible pavements and 4.5 for rigid pavements. Once po and pt are established, Equation 2.10 can be used to define the total change in serviceability index for any road surfacing: ∆𝑷𝑺𝑰 = 𝒑𝒐 − 𝒑𝒕 . . . . . . . . . . . . . . . . . . . (2.10)
23 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
2.3.2.2 Allowable Rutting The rut depth failure predicted by the aggregate surfaced road model does not refer to simple surface rutting (corrected by normal blading operations), but rather to serious rutting associated with deformation of pavement structure and roadbed support. [5] 2.3.2.3 Aggregate Loss For aggregate surfaced roads, an additional concern is the aggregate loss due to traffic and erosion unlike paved roads. When aggregate loss occurs, the pavement structure becomes thinner and the load-carrying capacity is reduced. [5] Down here, two equations are presented. Equation (2.11) can be used for sections experiencing greater than 50 percent truck traffic, and Equation (2.12) for typical rural sections: GL=0.12+0.1223 (LT). . . . . . . . . . . . . . . (2.11) Where: GL = total aggregate loss in inches, LT = number of loaded trucks in thousands. B
GL=
(25.4)
3380.6
(0.0045LADT+ R + 0.467G
. . . . . . . . . . . . . . (2.12)
Where: GL = aggregate loss, in inches, during the period of time being considered, B = number of bladings during the period of time being considered, LADT = average daily traffic in design lane, R = average radius of curves, in ft, and G = absolute value of grade, in percent. Again, Equation (2.13) can be used for sections that exhibit very little truck activity compared to cars.
AGL = [
T2 2
T + 50
] x f (4.2 + 0.092T + 0.889R2 + 1.88VC). . . . . (2.13)
Where: AGL = annual aggregate loss, in inches, T =annual traffic volume in both directions, in thousands of vehicles, R = annual rainfall, in inches, VC = average percentage gradient of the road, f = 0.037 - laterite, 0.043 - quartzite, 0.028 - volcanic & 0.059 - coral gravels. Apart from the above three AASHTO (1993) performance requirements, other research factors in the area also affect design outputs. As of NCHRP (Performance of Pavement Subsurface Drainage, 2002), the use of subsurface drainage features substantially increases the cost of new and rehabilitated pavements and raises the question whether the increased construction cost is offset by a proportional increase in pavement performance. [13] And again Ezgi Yurdakul (2013) suggests the addition of supplementary cementitious materials (SCMs) can help improve workability, long-term strength, and durability in Portland cement concrete (PCC) pavements.[14] 24 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
2.3.3 Material Properties for Structural Design 2.3.3.1 Effective Roadbed Soil Resilient Modulus It is the basis for materials characterization is elastic or resilient modulus. For roadbed materials, laboratory resilient modulus tests (AASHTO T 274) should be performed on representative samples in stress and moisture conditions simulating those of the primary moisture seasons. Alternatively, the seasonal resilient modulus values may be determined by correlations with soil properties, i.e., clay content, moisture, PI, etc for the purpose of quantifying the relative damage a pavement is subjected to during each season of the year and treat it as part of the overall design. An effective roadbed soil resilient modulus is then established which is equivalent to the combined effect of all the seasonal modulus values. Two different procedures for determining the seasonal variation of the modulus are widely known: The first approach is to obtain a laboratory relationship between resilient modulus and moisture content. Alternatively, calculate the resilient modulus for different seasons and with coefficient of variations greater than 0.15 (within a season) should be subdivided into smaller sections. Besides defining the seasonal moduli, it is also necessary to separate the year into various time intervals during which different moduli are effective. This gives the equivalent annual damage obtained by treating each season independently in the performance equation and summing the damage. The effective roadbed soil resilient modulus (MR), then, is the value corresponding to the average relative damage on the MR- uf scale. Part II, Section 2.3 of AASHTO (1993) can be referred for detail. [5] 2.3.3.2 Effective Modulus of Subgrade Reaction Like the effective roadbed soil resilient modulus for flexible pavement design, an effective modulus of subgrade reaction (k-value) will be developed for rigid pavement design. Since the k-value is directly proportional to roadbed soil resilient modulus, the season lengths and seasonal moduli developed in the previous section will be used as inputs to the estimation of an effective design k-value. [5] 2.3.3.3 Pavement Layer Materials Characterization Thus, resilient modulus refers to the material’s stress-strain behavior under normal pavement loading conditions. The strength of the material is important in addition to stiffness, and future mechanistic based procedures may reflect strength as well as stiffness in the materials’ characterization procedures. In addition, stabilized base materials may be subject to cracking under certain conditions and the stiffness may not be an indicator for this distress type. Different notations are used to express the moduli for subbase (ESB), base (EBS), asphalt concrete (EAC), and Portland cement concrete (Ec).[5] Because of the small displacements and brittle nature of the stiffest pavement materials, i.e., Portland cement concrete and those base materials stabilized with high cement content, 25 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
it is difficult to measure the modulus using the indirect tensile apparatus. Thus, it is recommended that the elastic modulus of such highly stiff materials be determined according to the procedure described in ASTM C 469. [5] The elastic modulus correlation recommended by the American Concrete Institute (ACI) for normal weight Portland cement concrete: Ec = 57,000 (fc) 0.5. . . . . . . . . (2.14) Where: Ec = PCC elastic modulus (in psi), and fc = PCC compressive strength (psi) 2.3.3.4 PCC Modulus of Rupture The modulus of rupture (flexural strength) of Portland cement concrete is required only for the design of a rigid pavement. It is the mean value determined after 28 days using thirdpoint loading (AASHTO T 97, ASTM C 78).Because of the treatment of reliability in AASHTO 1993 Guide, it is strongly recommended that the normal construction specification for modulus of rupture (flexural strength) not be used as input, since it represents a value below which only a small percent of the distribution may lie. If it is desirable to use the construction specification, then some adjustment should be applied, based on the standard deviation of modulus of rupture and the percent (PS) of the strength distribution that normally falls below the specification: Sc’ (mean) = Sc + z (SDs). . . . . . . . . (2.15) Where: Sc’ = mean value of rupture modulus (psi), Sc=construction specification on modulus of rupture (psi), SDs = estimated standard deviation of modulus of rupture (psi), z = standard normal variate: = 0.841, for PS = 20 %, = 1.037, for PS = 15 %, = 1.282, for PS = 10 %, = 1.645, for PS = 5 %, and = 2.327, for PS = 1 % 2.3.3.5 Layer Coefficients It describes a method for estimating the AASHTO structural layer coefficients (ai values) required for standard flexible pavement structural design. A value for this coefficient is assigned to each layer material in the pavement structure in order to convert actual layer thicknesses (Di) into structural number (SN). Since our main concern is rigid pavements, we shall leave this section for further reading of AASHTO guide and ASTM standards.[5] 𝑺𝑵 = ∑𝒊=𝟏 𝒂𝒊 𝑫𝒊 . . . . . . . . . (2.16)
2.3.4 Pavement Structural Characteristics 2.3.4.1 Drainage This section describes the selection of inputs to treat the effects of certain levels of drainage on predicted pavement performance. Table 2.6 below contains the general definitions corresponding to different drainage levels based on the duration water requires draining off of pavement structures:
26 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 2.6: different drainage levels from the pavement structure (Source: AASHTO, 1993) Quality of Drainage Excellent Good Fair Poor Very Poor
Water Removed Within 2 Hours 1 Day 1 Week 1 Month Water will not drain
For Rigid Pavements, drainage is quantified by using a drainage coefficient, Cd, in the performance equation of AASHTO, 1993. Table 2.7 provides the recommended Cd values depending on the quality of drainage and the percent of time during the year the pavement structure would normally be exposed to moisture levels approaching saturation. [5] Table 2.7: Recommended Values of Drainage Coefficient, Cd, for Rigid Pavement Design (Source: AASHTO, 1993) Percent of Time Pavement Structure is Exposed to Moisture Levels Approaching Saturation Quality of Drainage Less Than 1% 1 – 5% 5 – 25 % Greater Than 25 % Excellent 1.25-1.20 1.20-1.15 1.15-1.10 1.10 Good 1.20-1.15 1.15-1.10 1.10 - 1.00 1.00 Fair 1.15-1.10 1.10-1.00 1.00 -0.90 0.90 Poor 1.10 – 1.00 1.00-0.90 0.90-0.80 0.80 Very Poor 1.00 – 0. 90 0.90-0.80 0.80-0.70 0.70 2.3.4.2 Load Transfer The load transfer coefficient, J, is a factor used in rigid pavement design to account for the ability of a concrete pavement structure to transfer (distribute) load across discontinuities, such as joints or cracks. Load transfer devices, aggregate interlock, and the presence of tied concrete shoulders all have an effect on this value. As a general guide for the range of J-values, higher ones should be used with low k-values, high thermal coefficients (α), and large variations of temperature (∆T). If dowels are used, the size and spacing should be determined by the local manual procedures and/or experience. As a general guideline, the dowel diameter should be equal to the slab thickness multiplied by 1/8 inch. The dowel spacing and length are normally 12 inches and 18 inches respectively. [5] i. Jointed Pavements The value of J recommended for a plain jointed pavement (JCP) or jointed reinforced concrete pavement (JRCP) with some type of load transfer device (such as dowel bars) at
27 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
the joints is 3.2. This value is indicative of the load transfer of jointed pavements without tied concrete shoulders. For jointed pavements without load transfer devices at the joints, a J-value of 3.8 to 4.4 is recommended. (This basically accounts for the higher bending stresses that develop in undowelled pavements, but also includes some consideration of the increased potential for faulting.) If the concrete has a high thermal coefficient, then the value of J should be increased. On the other hand, if few heavy trucks are anticipated as in the case of a low-volume road, the J-value may be lowered since the loss of aggregate interlock will be less. [5] ii. Continuously Reinforced Pavements The value of J recommended for continuously reinforced concrete pavements (CRCP) without tied concrete shoulders is between 2.9 to 3.2, depending on the capability of aggregate interlock (at future transverse cracks) to transfer load. In the past, a commonly used J-value for CRCP was 3.2. But with better design for crack width control, each agency is advised to develop its own criteria based on local aggregate and temperature ranges. [5] iii. Tied Shoulders or Widened outside Lanes. One of the major advantages of using tied PCC shoulders (or widened outside lanes) is the reduction of slabs tress and increased service life they provide. To account for this, significantly lower J-values may be used for the design of both jointed and continuous pavements. For continuously reinforced concrete pavements with tied concrete shoulders (the minimum bar size and maximum tie bar spacing should be the same as that for tie bars between lanes), the range of J is between 2.3 & 2.9, with a recommended value of 2.6. [5] 2.3.4.3 Loss of Support (LS) This factor, LS, is included in the design of rigid pavements to account for the potential loss of support arising from subbase erosion and/or differential vertical soil movements. It is treated in the actual design by diminishing the effective or composite k-value based on the size of the void that may develop beneath the slab. Obviously, if various types of base or subbase are to be considered for design, then the corresponding values of LS should be determined for each type. The LS factor should also be considered in terms of differential vertical soil movements that may result in voids beneath the pavement. Thus, even though a non erosive subbase is used, a void may still develop, thereby reducing pavement life. Generally, for active swelling clays or excessive frost heave, LS values of 2.0 to 3.0may be considered. [5]
28 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
2.3.5 Reinforcement Variables Because of the difference in the reinforcement design procedures between jointed and continuous pavements, the design requirements for each are separated into two sections. In addition to dimensions, consideration should be given to corrosion resistance of reinforcement, especially in areas where pavements are exposed to variable moisture contents and salt encounters. [5] 2.3.5.1 Jointed Concrete Pavements There are two types of rigid pavement which fall under the “jointed” category: plain jointed pavement (JCP), which is designed not to have steel reinforcement, and jointed reinforced concrete pavement (JRCP), which is designed to have significant steel reinforcement, in terms of either steel bars or welded steel mats. The steel reinforcement is added if the probability of transverse cracking during pavement life is high due to such factors as soil movement and/or temperature/moisture change stresses. For the case of plain jointed concrete pavements (JCP), the joint spacing should be selected at values so that temperature and moisture change stresses do not produce intermediate cracking between joints. The maximum joint spacing will vary, depending on local conditions, subbase types, coarse aggregate types, etc. In addition, the maximum joint spacing may be selected to minimize joint movement and, consequently, maximize load transfer. Each agency’s experience should be relied on for this selection. Following are the criteria needed for the design of jointed reinforced concrete pavements (JRCP). These criteria apply to the design of both longitudinal and transverse steel reinforcement. [5] i. Slab Length This refers to the joint spacing or distance, L (feet or meter), between free (untied) transverse joints. It is an important design consideration since it has a large impact on the maximum concrete tensile stresses and, consequently, the amount of steel reinforcement required. Because of this effect, slab length (joint spacing) is an important factor that must be considered in the design of any reinforced or unreinforced jointed concrete pavement. ii. Steel Working Stress This refers to the allowable working stress, f, in the steel reinforcement. Typically, a value equivalent to 75 percent of the steel yield strength is used for working stress. The minimum wire size should be adequate so that potential corrosion does not have a significant impact on the cross-sectional area. iii. Friction Factor This factor, F, represents the frictional resistance between the bottom of the slab and the top of the underlying subbase or subgrade layer and is basically quantified by coefficient of friction. 29 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
2.3.5.2 Continuously Reinforced Concrete Pavements The principal reinforcement in continuously reinforced concrete pavements (CRCP) is the longitudinal steel which is essentially continuous throughout the length of the pavement. This longitudinal reinforcement is used to control cracks which form in the pavement due to volume change in the concrete. We may be using either reinforcing bars or deformed wire fabric. It is the restraint of the concrete due to the steel reinforcement and subbase friction which causes the concrete to fracture. A balance between the properties of the concrete and the reinforcement must be achieved for the pavement to perform satisfactorily. The evaluation of this interaction forms the basis for longitudinal reinforcement design. The purpose of transverse reinforcement in a CRC pavement is to control the width of longitudinal cracks which may possibly develop. Transverse reinforcement may not be required for CRC pavements in which no longitudinal cracking is likely to occur based on observed experience of concrete pavements with similar conditions. However, if longitudinal cracking does occur, transverse reinforcement will restrain lateral movement and minimize the deleterious effects of a free edge. Transverse reinforcement should be designed based on the same criteria and methodology used for jointed pavements. The following are the requirements for the longitudinal reinforcement design in CRC pavements. [5] i. Concrete Tensile Strength Two measures of concrete tensile strength are available. The modulus of rupture or flexural strength derived from a flexural beam test which is used for determination of the required slab thickness and the indirect tensile test (covered under AASHTO T 198 and ASTM C 496 test specifications) that governs the required steel. The 28th day values should be used for both. Also, these two strengths should be consistent with each other. The indirect tensile strength will normally be about 86 percent of concrete modulus of rupture. ii. Concrete Shrinkage Drying shrinkage in the concrete resulting from water loss is a significant factor in the reinforcement design. Other factors affecting shrinkage include cement content, chemical admixtures, curing method, aggregates, and curing conditions. The value of shrinkage at 28 days is used for the design shrinkage value. Both shrinkage and strength of the concrete are strongly dependent upon the water-cement ratio. As more water is added to a mix, the potential for shrinkage will increase and the strength will decrease. Thus, shrinkage can be considered inversely proportional to strength.
30 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
iii. Concrete Thermal Coefficient The thermal coefficient of expansion for Portland cement concrete varies with such factors as water-cement ratio, concrete age, richness of the mix, relative humidity, and the type of aggregate in the mix. In fact, the type of coarse aggregate has the most significant influence. iv. Bar or Wire Diameter No 5 (15.9 mm) and No 6 (19.1 mm) deformed bars are extensively used for longitudinal reinforcement and No 6 bar is the largest practical size to meet bond requirements and control crack widths. v. Steel Thermal Coefficient Unless specific knowledge of the thermal coefficient of the reinforcing steel is available, a value in AASHTO, 1993 can be referred and used for design purposes. vi. Design Temperature Drop The temperature drop used in the reinforcement design is the difference between the average concrete curing temperature and the design minimum temperature. The average concrete curing temperature may be taken as the average daily high temperature during the month the pavement is expected to be constructed. This average accounts for the heat of hydration. The design minimum temperature is defined here as the average daily low temperature for the coldest month during the pavement life. The design temperature drop which is incorporated in the longitudinal reinforcement design procedure is: 𝑫𝑻𝑫 = 𝑻𝑯 − 𝑻𝑳 . . . . . . . . . (2.17) Where:
DTD =design temperature drop, OF, TH =average daily high temperature during the month of pavement construction, o F, and TL =average daily low temperature during the coldest month of the year, oF.
vii. Friction Factor The criterion for the selection of a slab-base friction factor for CRC pavements is the same as that for jointed pavements. [5]
2.4 Economic Analysis Economic efficiency in pavement design is still just as vital as ever but achieving it now requires a more sophisticated approach. Instead of simply minimizing initial cost, it is also necessary to consider the long term user and maintenance benefits of the various alternatives available. The modern concrete pavement has been improved and now provides significant road user benefits as well as the traditionally recognized advantages of great durability and lower maintenance costs (Cement & Concrete Association of New Zealand, 2002). [15] 31 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
2.4.1 Economical Implications of Using Rigid Pavement 2.4.1.1 Initial Cost Computing the initial cost of construction involves the calculation of material quantities to be provided in each pavement structure and multiplication by their unit prices. Material quantities are generally direct functions of their thicknesses in the structure. They are also functions of thicknesses of other layers and the width of pavement and shoulders. As a general rule of thumb, for large scale projects, concrete pavements are economically most favorable if the subgrade is soft and the traffic volume is high. This is because subgrade stiffness and traffic volumes affect the thickness of a concrete pavement design much less than they do a flexible pavement design. Of course, the initial cost of rigid pavements is likely to outweigh its flexible counterpart. But, as shall be discussed in subsequent sections, initial cost is only one part of the overall decisive factor. At the other end of the scale, minor roads with difficult access for conventional road-making plant, may sometimes be economic to construct in concrete (Cement & Concrete Association of New Zealand, TR12, 2002). [15] 2.4.1.2 Future Maintenance Expenditure Prediction Low future maintenance is one of the principal advantages of concrete pavements. There are examples of well designed and constructed concrete pavements that have required little or no maintenance well beyond their 40 year design lives. As a general rule, the analyst who is comparing the economics of flexible and rigid pavement options should take particular care to correctly identify the future flexible pavement costs. These generally will be considerably higher than the rigid option costs, leading to significantly larger figures. It is easy, especially with heavily trafficked flexible pavements, to underestimate future maintenance necessary to meet designed standards of skid resistance and silence (Cement & Concrete Association of New Zealand, 2002). [15] On heavily trafficked routes, it is essential to consider the mutual interaction between maintenance costs and traffic delay costs. Traffic delays should be considered and costs included in the analysis. This means that by using rigid pavements, future delay costs arising from regular maintenance can be minimized and as well, the travel time and vehicle operating costs associated with maintenance should not be underestimated. 2.4.1.3 Rolling Resistance and Fuel Consumption Fuel consumption is a major factor in the economics of highways. The rolling resistance of the pavement is an important contributor to the fuel consumption and the corresponding CO2 production. The major influences on rolling resistance are the surface macro-texture, the mega-texture, the road roughness and the rigidity of the surface. When a heavy truck travels over flexible pavement, energy is consumed in deflecting the pavement and subgrade, resulting in increased fuel consumption. But it can be used economically on rigid pavements.
32 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
2.4.1.4 Early Completion Rigid pavements are constructed considerably faster than the asphalt option - a single slipform paver being able to lay up to 1.5 km of subbase or base per day (Cement and Concrete Association of New Zealand, 2002). Depending on the position of the pavement construction on the Program, this leads to an accelerated opening to traffic and an earlier benefit flow. Shorter construction duration has its own positive impact on the society. [15] We, as Ethiopians, are no strangers to road constructions taking a very long time to complete. The associated inconvenience imposed on the community is quite frustrating and has negative economical implications.
2.4.2 How to Analyze Pavement Costs It is crucial in economic evaluation to include all costs occurring during the life of the facility under investigation. Life-cycle costs refer to all costs (and, in the complete sense, all benefits) which are involved in the provision of a pavement during its complete life cycle (AASHTO, 1993).These include construction costs, maintenance costs, rehabilitation costs, etc. [5] Mostly, the initial construction cost is the main consideration; the future maintenance and rehabilitation costs may sometimes be forgotten. It would be helpful to make a case of this by an example involving a person who is thinking about purchasing a private vehicle. Once that person decides to acquire one, he will realize that the costs involved in owning a car include (1) purchase price, (2) gasoline and operating costs, such as buying tires,(3) repairs (maintenance), (4) trade in value (salvage), etc. Similar comparison should be recognized for pavements. Also required is consideration of useful life of the car. An inexpensive car may last 5 years while an expensive one, carefully selected, may last 20 years. Since all of these costs do not occur at the same time, it is useful to determine the amount of money which could be invested at a fixed time (usually the beginning) and would earn enough money at a specific interest rate to permit payment of all costs when they occur. Thus, an interest rate or time value of money becomes important in calculation. Life cycle costs then can be expressed as a term that holds together all immediate and recurring costs that a certain pavement type poses throughout its complete life time. Table 2.8: Costs Typically Considered in Life-Cycle Cost Analysis Agency Costs
User Costs Associated With Work Zones
Design and Engineering Land Acquisition Construction Reconstruction/Rehabilitation Preservation/Routine Maintenance
Delays Crashes Vehicle Operating Costs
33 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
2.4.3 Factors Involved in Pavement Costs and Benefits AASHTO, 1993guide provides a detailed list of different cost and benefit categories that need to be considered in order to carry out a successful economical analysis. The major initial and recurring costs that should be considered in the economic evaluation of alternative pavement strategies include the following: Agency costs (Initial & Future construction/rehabilitation cost (overlays, seal coats, reconstruction, etc., Maintenance costs, recurring throughout the design period, Salvage return/residual value at the end of the design period (may be a “negative cost”), Engineering and administration costs), User costs(Travel time, Vehicle operation, Accidents, Discomfort, Time delay & extra vehicle operating costs during resurfacing/major maintenance) and Traffic control costs(if any). i. Agency Costs Initial Construction Costs: direct expenditures related to the materials of construction, equipment acquisition, labor hiring, plant establishment, testing requirements and the like. They are widely known and seem to be the governing factors for pavement selection in underdeveloped countries like Ethiopia. However, agency costs encompass more than just initial construction cost. The cumulative effect of all costs involved shall be the governing factor in choosing pavement type. Maintenance and rehabilitation costs: includes materials, equipment, staff and crew salaries etc. The timing and frequency are also crucial determining factors because they have implications on the resource to be expended during renovation. For example, in the case of our country, Ethiopia, if maintenance of a certain pavement is to be carried out during the rainy season because of coercive conditions, the cost of maintenance would be higher compared to a similar maintenance carried out during one of the drier months. Some agencies do not include maintenance and operation costs in their life cycle cost analysis (LCCA) of pavements, but exclusion of these costs would mean inaccurate results in the end, especially when comparing asphalt and concrete pavements. This is mainly because the difference between asphalt and concrete pavements is primarily due to differences in maintenance and rehabilitation costs (Asta Guciute Scheving, 2011).[16] Sometimes planned maintenance costs can be included when designers purposely decide to elongate the life of a certain newly designed pavement so that it can achieve its full life time. For example, a certain road section may have a life period of 50 years. Engineers may initially design that pavement to perform substantially for 35 years and then complete the remaining 15 years by carrying out major maintenance at the 35th year. Salvage or Residual Value: The pavement worth that the agency has at the end of the LCCA period is called the salvage value (ArvoTinni, 2013). With the depletion of resources all over the world, such materials can become increasingly important in the future, especially when used in a new pavement by reworking or reprocessing. [17] Salvage value of a material depends on several factors, such as volume and position of the material, contamination, age or durability, anticipated use at the end of the design period, 34 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
etc. It is best to represent it as a percentage of the original cost. Salvage value can be relatively easy to calculate; however, the choice of values to be assigned will pose a problem for the analyst (AASHTO, 1993). For example, what value to assign to a 15-yearold base or a moderately damaged asphalt concrete which is 10 years old. [5] ii.
User Costs
By these costs, we can see the impact of road works on road users and they will differ during maintenance and rehabilitation periods in which they can increase dramatically. It is obvious that road works cause delay and increase vehicle operating costs, as well as traffic accidents. In countries like ours, agencies seem to hardly even know the concept of user costs. There is such a poor practice of neglecting user costs during analysis of a pavement to be constructed. User costs can be divided into following categories: Vehicle operating costs: Mostly as a result of increased fuel usage, wear on tires and other parts, and other related factors, vehicle operating costs increase during maintenance periods. In-service vehicle operating costs are a function of pavement serviceability level, which is often difficult to estimate (Tapan, 2002). [18] User delay costs: are connected with road users' time. Usually time saving is mentioned as one of the key benefits in transportation projects. User costs mostly increase during maintenance and rehabilitation periods, when traffic is completely shut down or diverted. Time delay cost is mostly due to changes in speed and are the additional cost of slowing from one speed to another and returning to the original speed (Walls & Smith, 1998). [19] Time value depends on the vehicle type and the purpose of the trip (USDOT, 1997). [20] However, user delay costs are one of the most difficult and controversial LCCA parameters: they are extremely difficult to calculate because it is necessary to put a monetary value on individuals' delay time (Walls & Smith, 1998). [19]And that seems to be the reason why there is still no globally accepted way of calculating them. Crash costs: include damage to the users’ and others’ vehicles and public/private property, as well as injuries (Tapan, 2002). Road accident cost is usually calculated from accident rate and economic costs specified for various of accident types and functional road classes.[18] Sometimes, even in the developed countries, certain LCCA models fail to include vehicle operation costs/crash costs due to lack of properly recorded data.
2.4.4 Economic Comparison of Rigid and Flexible Pavements The steps involved in the LCCA methods are as follows (Walls & Smith, 1998): first define realistic design options, i.e. rigid and flexible pavement for a certain route. For each option, it is important to identify initial construction costs, predict future rehabilitation and maintenance activities and consider the timing of those individual actions. The timing is quite important because some seasons are friendlier than others in construction activities. [19] Hence, a plan of activities must be created for each design option.
35 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
The next step is to estimate costs for all activities. It is recommended to include not only direct agency expenses but also user costs, in order to get a better picture of the impact of maintenance/repair (Hass et. al 2005).[21] This is a key factor that needs to be adopted into the practice of the road construction and decision making organs of our country. After cost is defined for every possible option, then the total life-cycle costs for each competing alternative can be calculated. LCCA uses discounting to convert future costs to present values so that the lifetime costs of different alternatives can be directly compared (Boardman et. al 2006). All costs in LCCA are divided into four groups: construction, agencies, user and environmental costs. [22] The first three are very crucial in determining the type of pavement to be used. In the context of Ethiopia, leaving out the last would be an acceptable option. But we need to start paying attention to the first three. These costs are individually calculated for each competing alternative. If one of the alternatives does not include a certain cost, then the others should also exclude this cost: only then can the alternatives be fairly compared. For example, if one alternative includes road markings into LCCA, then the other alternatives must include road markings too. Some of the costs can be difficult to quantify, so their inclusion in the project can be optional. To be able to fairly compare all opportunities, the discount rate and analysis period should be the same for all alternatives (FHWA, 2002). [23] There are different mathematical methods to compare life cycle costs (see Section 2.4.6). Now, having the overall costs of both the rigid and flexible pavements at hand, the final step would be to pass on a provisional decision as to which one to use. If results differ by more than 10%, then the one with the lower cost appears to be a good choice. However, if results are within 10 % of each other, both should be regarded as comparable (Arvo Tinni 2013). If that occurs, a subsequent stage of comparisons must be carried out to cover political, social and environmental issues like: Speed of construction; Urgency of availability; Disruption to traffic; Disruption to commercial activity; Noise during construction and subsequent traffic noise; Vibration, dust and fumes during construction; Sustainability issues; and Design reliability (uncertainty in traffic estimates, unsuitable in situ construction materials, variations in pavement layer thicknesses &accuracy of design methods for different pavements). [17]
2.4.5 Cautions in Using LCCA As with any kind of analysis or research, it is important to understand which parameters make the biggest contribution to the final results. For example: the pavement subgrade strength and traffic loading have the major impact on the design outcome in the pavement design procedure. For LCCA, many variables can affect the final net present worth (NPW) for a pavement alternative. For instance, the unit price of a material is very important and can cause an alternative to go from the lowest NPW to the highest. Therefore, it is very important to use reasonable unit prices that reflect reality. [16]
36 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Other factors that can greatly influence the LCCA results are the discount rate, analysis period and timing of activities (Buncher, 2004). By changing some parameters, it is relatively easy to find out which inputs have major impacts on the final results. [24]
2.4.6 Methods of Economic Analysis Among those applicable to the evaluation of alternative pavement design strategies, some include: Equivalent uniform annual cost method, or the annual cost method, Rate of return method, Benefit cost ratio method and Cost effectiveness method. A common feature of these methods is the ability to consider future streams of costs and benefits. The following are several basic considerations in selecting the most appropriate (but not necessarily the best) method for economic evaluation of alternative pavement strategies. They may be questions like: How important is the initial capital expenditure in comparison to future expected? What method of analysis is most understandable to the decision maker? What method best suits the requirements of the particular project involved? and Are benefits (such as taxes from additional road users) included in the analysis? Equations for Economic Analysis In this thesis, only the Annual Cost (Equivalent Uniform Annual Cost) method of analysis is presented because of its wide applicability and acceptance. The material has been adapted from (Haas and Hudson), who also present details of the remaining methods of economic analysis for further comparison. The AASHTO Manual on User Benefit Analysis also presents comprehensive details for those desiring more information. Equivalent Uniform Annual Cost Method The equivalent uniform annual cost method combines all initial capital costs and all recurring future expenses into equal annual payments over the analysis period. It can be expressed as in the following equation: ACx1,n = crfx1 (ICC)x1 + (AAMO)x1 + (AAUC)x1 –crf i,n (SV)x1,n . . . . . (2.18) Where: ACx1,n = equiv. uniform annual cost for xl, for an analysis period of n years, crfi,n = capital recovery factor for interest rate i and n years,
𝒊 (𝟏 + 𝒊)𝒏 (𝟏 + 𝒊)𝒏 − 𝟏
(ICC)x1 = initial capital costs of construction (AAMO) x1 = average annual maintenance plus operation costs for alternative xl (AAUC) x1 = average annual user costs for alternative x1 (including vehicle operation, travel time, accidents and discomfort if designated), and (SV) x1,n =salvage value, if any, for alternative x1 at the end of n years.
37 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
References TO CHAPTER TWO [1]
Huang, Yang H. (2004), Pavement Analysis & Design, 2nd Edition - Pearson Education, Inc. – New Jersey, U.S.A. (Pp. 5 – 8)
[2]
Larralde, J. S. (1985), Structural Analysis of Rigid Pavements, FHWA/IN/JHRP85/04. Joint Highway Research Project, Indiana Department of Transportation and Purdue University , West Lafayette, Indiana, U.S.A. (Pp. xiv & 96)
[3]
Darestani, M. Y. et al (2006), Experimental Study on Structural Response of Rigid Pavements Under Moving Truck Load, Research into Practice - Department of Urban Design, Queensland University of Technology, Australia (Pp. 12 – 14)
[4]
Kumar, Suresh et al (2012), Fatigue Analysis of High Performance Cement Concrete for Pavements using the Probabilistic Approach, International Journal of Emerging Technology and Advanced Engineering - ISSN 2250-2459, Volume II, Issue 11, Bangalore, India(Pp. 1 – 2)
[5]
AASHTO, American Association of State Highway & Transportation Officials (1993), Guide for the Design of Pavement Structures, Capitol Street – Washington D.C., U.S.A.(Part I & II)
[6]
ERA, Ethiopian Road Authority (2002), Pavement Design Manual – Volume II, Addis Ababa, Ethiopia (Pp. 14)
[7]
Guyer, J. Paul (2009), Introduction to Rigid Pavement Design, Continuing Education and Development, Inc., Stony Point, New York, U.S.A.
[8]
Paul Franta, Daniel (2012), Computational Analysis of Rigid Pavement Profile, Msc Thesis - University of Minnesota, Minnesota U.S.A. (Pp. 74)
[9]
Delate, Norbert (2008), Concrete Pavement Design, Construction and Performance, 1st Edition, Taylor and Francis – New York, U.S.A.(Pp. 10 - 11)
[10] Griffith, Geoffrey & Thom, Nick (2007), Concrete Pavement Design Guidance Notes, 1st Edition, Taylor and Francis – New York, U.S.A. (Pp. 7 - 12) [11] Packard, Robert G. (1995), Thickness Design for Concrete Highway and Street Pavements, 2nd Edition, Portland Cement Association (PCA)(Pp. 8)
38 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
[12] TRB, Transportation Research Board (2000), Highway Capacity Manual 2000 (HCM-2000), National Research Council - Washington D.C., U.S.A. (Pp. 7-1 – 7-4) [13] NCHRP, National Cooperative Highway Research Program (2002), Performance of Pavement Subsurface Drainage, Transportation Research Board, Washington D.C., U.S.A.(Pp. 6 - 7) [14] Yurdakul, Ezgi (2013), Proportioning for Performance Based Concrete Pavement Mixtures, PhD Dissertation – University of Iowa, Iowa, U.S.A.(Pp. 188 - 190) [15] Cement and Concrete Association of New Zealand (200?), The Economic Benefits of Concrete Road Pavements, Technical Report 12(TR 12) ISSN:1171-4204, ISBN:0908956207, (Pp. 3 - 5) [16] Asta Guciute Scheving, (2011), Life Cycle Cost Analysis of Asphalt and Concrete Pavements, Thesis - Master of Science (Pp. 7 - 8) [17] Arvo Tinni (2013), RFD, BE, FIAust, AIArbA, CPEng, Tinni Management Consulting Plc. (Pp 11 & 19) [18] Tapan, K. (2002), Life Cycle Cost Analysis, Wayne state university, Detroit, MI, U.S.A. [19] Walls, J. I., & Smith, M. (1998), Life-Cycle Cost Analysis in Pavement Design – Interim Technical Bulletin, Washington, DC: Pavement Division, Office of Engineering –Federal Highway Administration. [20] USDOT, U.S. Department of Transportation (1997), The Value of Saving Travel Time: Department Guidance for Conducting Economic Evaluation, Washington, D.C., U.S.A. [21] Hass, R., Tighe, S. L., &Falls, L. C. (2005), Beyond Conventional LCCA: Long Term Return on Pavement Investments,2005 Annual Conference of the Transportation Association of Canada. Calgary [22] Boardman, A., Greenberg, D., Vining, A., & Weimer, D. (2006), Cost Benefit Analysis: Concepts and Practice, New Jersey: Pearson Prentice Hall. [23] FHWA, (2002) Life-Cycle Cost Analysis Primer, Washington, DC: United States Department of Transportation - Federal Highway Administration. [24] Buncher, M. (2004), ASPHALT. Retrieved 10 26, 2010, from the online magazine of The Asphalt Institute: http://www.asphaltmagazine.com/archives/2004/summer/ state_art_pavement_type_selection.pdf 39 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
CHAPTER THREE RESEARCH METHODOLOGY & PROCEDURES 3.1 Introduction Extracting reliable findings from a certain research requires a set of systematic methods and procedures. In order for this research to meet its goals, especially with regard to putting a firm set of concepts towards the implication of Rigid Pavements in Ethiopia, the researchers have made their efforts in closely inspecting the case study picked. In doing so, relevant secondary data were collected as can be inferred from Chapter 4. These data have been extensively used in combination with the methods and procedures presented in this chapter from Sections 3.2 to 3.7. The researchers responsible for this paperwork believe that the findings could have been even sounder if ERA Pavement Design Manual (Volume II, 2002) had been a more complete document and different researches incorporating local conditions (especially vehicle axle load surveys) were widely available in the country. For such reasons, the AASHTO (Guide for the Design of Pavement Structures, Volume I, 1993) is the pillar of this research when comes to rigid pavement design approaches as was mentioned in Section 1.3. However, different research reports, institutional and organizational journals, books and other manuals have been cited in different sections of the previous and subsequent chapters for comparison of several terminologies, thus making a bit more complete sense. And apart from collected data (on secondary basis) and review of different literatures, the Visual Studio (2008) and common LISP programming languages were utilized to come up with the Software we developed & Structural Design Catalogs that were drawn from it. Generally speaking, the methods used to conduct this research include: Review of different literatures: manuals (majorly the AASHTO, 1993 guide), journals, reports, researches and books, Collection of Secondary Data: relevant climatic, traffic, soil etc about the area and The Visual Studio (2008) and common LISP: for the developed design software. The following sections thoroughly explain the different design procedures adopted in this research.
40 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
3.2 AASHTO Design Procedure for Rigid Pavement Design This procedure assumes the pavement is being subjected to traffic loads in excess of 50,000 80KNequivalent single axle loads (ESAL) over the performance period and puts emphasis on one particular type of concrete pavement, namely jointed reinforced concrete pavement (JRCP). [1] The procedure is divided into sections, each with one or more steps so as to make the explanation clearer and the algorithm for the research software program easier to understand and implement.
3.2.1 Subgrade Reaction: k-value It is important to determine the type or magnitude of support the subgrade can provide before designing the slab as this would directly affect the design at later stages. This level of support is estimated by the effective modulus of subgrade reaction, k, which is measured in pressure per volume units (Pci, Kg/m3…). It requires estimating several input variables: roadbed soil resilient modulus, subbase characteristics: type, thickness and elastic resilient modulus, loss of support and relative damage among others. The following steps are generally followed to determine the previously mentioned parameters and other auxiliary dependencies. [1]
Step1: Input Variables 1. Subbase Types: entails cost effectiveness from different strengths or modulus values. 2. Subbase Thicknesses: evaluates alternatives so as to take economy into account. 3. Loss of support, LS: reduction in actual amount of support provided by the bed calls for a reduction of the k-value by a certain factor, called LS. 4. Depth to rigid foundation – the proximity of the bedrock to the subgrade surface. For each value assigned to the aforementioned variables, a separate design should be carried out so that the economical or optimized value can be selected.
Step2: Seasonal Roadbed Soil Resilient Modulus The roadbed moduli need to be determined from laboratory test results (for different moisture conditions of the year) or by correlating various material characteristics. An estimate of the insitu moisture conditions for each season leads to variation of these moduli. Once the seasonal roadbed soil moduli, MRi, are determined, the relative damage, Uf of the pavement for each seasonal value needs to be estimated with the following relation. Uf = 1.18 * 108 * MR-2.32 . . . . . . . (3.1) The effective seasonal roadbed soil modulus can be computed by averaging the seasonal relative damage values and evaluating Equation (3.1) for the corresponding average value of Uf.
41 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Step 3: Subbase Elastic Resilient Modulus, ESB For those types of subbase material which are insensitive to season, a constant value of subbase modulus may be assigned for each season and for those unbound materials which are sensitive to season but were not tested for the extreme conditions, values for ESB, of 50,000psi and 15,000 psi may be used for the frozen and spring thaw periods, respectively. However, this approach holds little significance to the Ethiopian case unless behavioral change of materials in different seasons is studied. For unbound materials, the ratio of the subbase to the roadbed soil resilient modulus should not exceed 4 to prevent an artificial condition.
Step 4: Composite Modulus of Subgrade Reaction, k This parameter is evaluated graphically by assuming a semi-infinite depth of the subgrade for each seasonal value of ESB and MR. Figure 3.1 can be navigated as follows: 1. Start from the selected subbase thickness and read ESB and MR simultaneously 2. Project the ESB value horizontally to the right 3. Project the MR value first horizontally to the right until it intersects the turning line and then project the intersection vertically upwards 4. The intersection of the simultaneously projected lines will be a point somewhere in the contours of composite k-values, from which the final value can be found by graphical interpolation.
Step 5: k-value for Shallow Pavement Foundations The modified k-value, considering the effect of rigid foundations near the surface, can be determined graphically from Figure 3.2. For foundations deeper than 10 feet (3.1m), this step can be disregarded. The procedure for navigating is as follows: 1. Start by reading the seasonal roadbed resilient modulus and then project the value vertically up until the subgrade depth curve is intersected(this depth could lie on some imaginary curve if the depth is different from two, five or ten feet) 2. Project the new point horizontally to a contour drawn for the unmodified k-value 3. Project the newly intersected point vertically down to read the modified k-value Note that this procedure has been incorporated because the strength of the underlying earth will somehow affect the effective modulus of subgrade reaction as long as it is situated within a depth of 3.1m.
Step 6: Relative Damage, Uf It evaluates the monthly damage to the pavement and its underlying structure. Figure 3.3can be directly used by taking an initial slab thickness in combination with the composite k-values.
42 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Step 7: Effective k-value If seasonal response data is available, the average Uf value along with the slab thickness can be used to directly read the effective k value from Figure 3.3.
Step 8: Loss of Support and Design k-value After computing or reasonably assuming the loss of support for the specified type of subbase material, the Design K-Value is determined from Figure 3.4. [1]
Figure 3.1: Chart for Composite Modulus of Subgrade Reaction, k (Source: AASHTO Design Guide, 1993)
43 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Figure 3.2: Chart to Modify Modulus of Subgrade Reaction to Consider Effects of Rigid Foundation near Surface (Source: AASHTO Design Guide, 1993)
44 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Figure 3.3: Chart for Estimating Relative Damage to Rigid Pavements Based on Slab Thickness and underlying Support (Source: AASHTO Design Guide, 1993)
45 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Figure 3.4: Chart for Correction of Effective Modulus of Subgrade Reaction for Potential Loss of Subbase Support (Source: AASHTO Design Guide, 1993)
3.2.2 Slab Thickness It may be estimated for each k-value identified in the previous sections through the use of predetermined nomographs. The following design parameters are also considered: 1. The Estimated Future Traffic, W18 2. Reliability, R 3. Total/Overall Standard Deviation, So: it is for any uncertainties present either in the estimated future traffic or pavement performance. For rigid pavements, a value of 0.35 is regularly used. 46 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
4. 5. 6. 7. 8.
AAiT, SCEE
Design Serviceability Loss, PSI = Pi-Pt (initial minus terminal) Concrete Elastic Modulus, Ec Concrete Modulus of Rupture, Sc’ Load Transfer Coefficient, J Drainage Coefficient, Cd
∆𝐏𝐒𝐈 ] 𝟒. 𝟓 − 𝟏. 𝟓 𝐥𝐨𝐠 𝟏𝟎 (𝐖𝟏𝟖 ) = 𝐙𝐑 𝐱 𝐒𝐨 + 𝟕. 𝟑𝟓 𝐱 𝐥𝐨𝐠 𝟏𝟎 (𝐃 + 𝟏) − 𝟎. 𝟎𝟔 + 𝟏. 𝟔𝟐𝟒 𝐱 𝟏𝟎𝟕 𝟏+ (𝐃 + 𝟏)𝟖.𝟒𝟔 𝐥𝐨𝐠 𝟏𝟎 [
𝐒𝐜′ 𝐱 𝐂𝐝 𝐱 (𝐃𝟎.𝟕𝟓 − 𝟏. 𝟏𝟑𝟐)
+ (𝟒. 𝟐𝟐 − 𝟎. 𝟑𝟐 𝐱 𝐩𝐭 ) 𝐱 𝐥𝐨𝐠 𝟏𝟎
𝟐𝟏𝟓. 𝟔𝟑𝐱 𝐉 𝐱 [𝐃𝟎.𝟕𝟓 − [
. . . (𝟑. 𝟐)
𝟏𝟖. 𝟒𝟐 ] 𝐄𝐜 𝟎.𝟐𝟓 ( ) ] 𝐤
Where: W18 = Predicted number of 18 kip equivalent single axle load applications, ZR = Standard normal deviate, So = Combined standard error of the traffic and performance prediction, D = Thickness (inches) of pavement slab, ΔPSI = Difference between the design serviceability indices, (initial & terminal) S’C = Modulus of rupture in psi for Portland Cement Concrete used on specific, J = Load transfer coefficient to adjust load transfer characteristics, Cd = Drainage coefficient, Ec = Modulus of elasticity (psi) for Portland cement concrete, and K = Modulus of subgrade reaction (pci). When these parameters are known, then the required slab thickness can be determined by using the nomograph presented in Figure 3.5and 3.6 or through Equation (3.2) (we may recall it from Section 2.2: Equation (2.1)): [1]
47 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Figure 3.5: Design Chart for Rigid Pavement, Segment 1 (Source: AASHTO Guide, 1993)
48 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Figure 3.6: Design Chart for Rigid Pavement, Segment 2 (Source: AASHTO Guide, 1993) 49 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
3.2.3 Joint Design Cement concrete pavements are designed and constructed with different types of joints for the permission of expansion and contraction of the pavement so as to reduce or relieve the stresses caused due to movements and environmental changes (expansion and contraction joints) and also to ease or facilitate the construction process. The following are general notes on jointed reinforced concrete pavements but Part II; Section 3.3 of AASHTO Guide (1993) can be referred for further design detail. [1] 3.2.3.1 Joint Types Generally, there are three different types of pavement joints, each with a specific purpose: Contraction joints: relieve the tensile stress due to climatic change or friction Expansion joints: when there is rise in temperature and changes in subgrade reaction, they prevent the development of excessive compressive stress (leading to pavement buckling) Construction joints: which are used to facilitate construction by allowing enough clearance for machines to pave the road section 3.2.3.2 Joint Geometry 1. Spacing: of transverse and longitudinal contraction joints depends on local conditions of materials and environment, whereas expansion joints are majorly dependent on layout and construction capabilities. Other factors are temperature changes, subbase frictional resistance, slab thickness and tensile/compressive strength of concrete. 2. Layout: Skewed layouts and randomization improves riding quality. 3. Dimensions: Normally joint dimensions are set by considering where the desired location of the crack should start. Depths of transverse contraction joints are usually ¼ of the slab thickness whereas longitudinal joints are to be 1/3 of the slab thickness. These joints are made by sawing and introducing inserts. The timing of joint formation is also of great importance. For example, contraction joints, used to control shrinkage cracking, should be sawed before slab shrinkage stresses become great enough to cause uncontrollable cracking. In case of machine sawing, the timing is crucial in order to avoid unwanted raveling and deformation of freshly cast concrete not yet strong enough to support sawing machines. 4. Sealant Dimensions: of contraction, expansion and construction joints [1]
50 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
3.2.4 Rigid Pavement Reinforcement Design Various environmental changes, namely, temperature spikes, moisture variations and frictional resistance from the bed material necessitate distributed steel reinforcements to halt the propagation of cracks. For jointed reinforced concrete pavements, both the transverse and longitudinal reinforcement areas are determined through the use of a simple nomograph (Figure 3.7). [1]The following parameters need to be known: Slab length, L: refers to the joint spacing or distance discussed in previous sections. Steel working stress, fs: is to be taken as 75 percent of the yield strength. Friction factor, F: this is the frictional resistance between the bottom of the slab and the top of the underlying soil or aggregate structure. Table 3.1: Recommended Values for Subbase and Subgrade Materials (Source: AASHTO Guide, 1993) Nature of material beneath slab
Friction Factor (F)
Surface treatment
2.2
Lime stabilization
1.8
Asphalt stabilization
1.8
Cement stabilization
1.8
River gravel
1.5
Crushed stone
1.5
Sandstone
1.2
Natural subgrade
0.9
51 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Figure 3.7: Reinforcement Design Chart for Jointed Reinforced Concrete Pavements(Source: AASHTO Guide, 1993)
3.3 ERA Design Procedures for Rigid Pavement As stated in Section 3.1, The ERA Pavement Design Manual (Volume II, 2002) is not a complete document for the purpose of this research, especially when comes to rigid pavement analysis and design. But in order to draw a contrast with the above procedure, we have listed some of the design methodologies down here that are recommended as a Rigid Pavement Design procedure in the manual.
3.3.1 Design life The structural property and durability of concrete slabs are very good and can allow design periods exceeding 40 years (up to 60 years). If properly designed and constructed, PCC pavements could last relatively long with a good level of serviceability and low maintenance requirements. Given that the required slab thickness varies linearly with the logarithm of the cumulative number of ESAs, designing for longer periods generally requires marginal addition of slab thickness and reinforcement, and thus, proves to be more economical overall. [2]
52 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
3.3.2 Design Traffic Loading As can be referred from Section 2.2.2.2, Table 2.1 was adopted from Table 1 of ERA Pavement Design Manual (Volume II, 2002). The equivalency factors are marginally higher, when compared with the corresponding values of ERA Pavement Design Manual Volume I (for Flexible Pavements, 2002), for loads up to the standard axle load. However, for heavier loads, the equivalency factors of rigid pavements are lower and the difference increases exponentially. This reflects the fact that rigid pavements are more resistant to heavy loads because of the capacity of the reinforced concrete slab to spread loads over a large surface of subbase. [2]
3.3.3 Thickness Design 3.3.3.1 Capping and Subbase A capping layer is required only if the CBR of the subgrade is 15% or less. The required thickness of a capping layer for a CBR value less than 15% can be obtained from Figure 3.8. The subbase layer is required when the subgrade material doesn’t comply with the requirement for a subbase (a CBR value of less than 30%) but it is almost always used to facilitate the provision of excellent level surface. Generally, the thickness of the subbase provided will be a constant 15 cm and can be cement stabilized. For a subgrade material with a CBR value less than 2%, there will definitely be a need for replacement and/or stabilization. A separation membrane (such as a polythene sheet) is required between the subbase and the concrete slab, mainly to reduce the friction between the slab and the subbase, thus inhibiting the formation of mid-bay cracks and loss of water from the freshly cast concrete. [2]
53 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Figure 3.8:Capping Layer and Subbase Thickness (mm) design(Source: ERA Pavement Design Manual Volume II (2002), as Adopted from THE DEPARTMENT OF TRANSPORT, London (1997), Design Manual for Roads and Bridges) 3.3.3.2 Concrete Slab Thickness and Reinforcement Making emphasis on Jointed Reinforced Concrete Pavement (JRCP), the thickness of concrete slab can be determined using Figure 3.9. The minimum thickness being 150 mm, the figure can also be used to determine the longitudinal reinforcement in terms of mm2/m for a given concrete slab thickness. Thus, several alternate combinations of concrete slab thickness and reinforcement area can be compared. In the absence of an effective lateral support provided by the shoulder adjacent to the most heavily trafficked lane, an additional slab thickness is required and can be determined using Figure 3.10. In addition to the longitudinal reinforcement, JRCP pavements shall be provided with transverse reinforcement consisting of 12 mm diameter steel bars at 600 mm spacing.2]
54 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Figure 3.9: Concrete Slab Thickness design(Source: ERA Pavement Design Manual Volume II (2002), as Adopted from THE DEPARTMENT OF TRANSPORT, London (1997), Design Manual for Roads and Bridges) 55 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Figure 3.10: Additional Concrete Slab Thickness without Lateral Support (Source: ERA Pavement Design Manual Volume II (2002), as Adopted from THE DEPARTMENT OF TRANSPORT, London (1997), Design Manual for Roads and Bridges)
3.3.4 Design for Movement 3.3.4.1 Transverse Joint Spacing For JRCP, contraction joints are generally provided at a standard spacing of 25m. Expansion joint are required at the limit with other pavement types or with structures like bridges. In the current section, expansion joints shall be avoided in casting the concrete slab at the hottest period of the year. If required, expansion joints shall replace every third contraction joint. [2] 3.3.4.2 Longitudinal Joint Spacing Longitudinal joints shall be placed at the edge of each traffic lanes. [2]
3.3.5 Design Detailing It shall be done as per the provision of Section 7.5 of ERA Pavement Design Manual (Volume II, 2002)
56 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
3.4 Unit Rate Estimation Procedures Unit Rate Analysis is a key tool in estimating respective expenditures of specific items in any type of construction. Likewise, this research uses such a tool in order to compare Rigid and Flexible Pavement structures in terms of their respective initial investments prior to the economical analysis. All the detail works are included in Chapter 5 but the major procedures to follow are listed and discussed here under. In order to finally estimate total construction cost (initial investment) of a pavement structure per kilometer, the respective construction materials to be utilized along with the required labor and equipments shall be assessed in detail. But unlike buildings, few of the reasons that make the estimation relatively less precise include: Road construction is equipment intensive and unlike labor, the expenditures required will be difficult to obtain in advance, The total extent of earthwork to be executed will only be an approximation (higher or lower operations will be encountered in real construction), Extraction of locally available materials for employment in the works of Capping Layer, Subbase, Base course, Aggregate Material for AC or PCC layer etc require extensive procedures in estimating: the Capacity of Quarry, Transportation Mechanism, Crushing & Mixing Plants, Physical & Chemical Properties, etc This research tries to cover all entities that are naturally incorporated in any detailed cost estimation. And in doing so, it adopts the specifications of ERA (Standard Technical Specification, 2002) and AASHTO (Guide Specifications for Highway Construction, 2008) for guidance in a combined manner. The following trades of works shall be assessed to determine a reasonable total project cost estimate. And their unit rate analysis is clearly shown in Chapter 5.
3.4.1 Preliminary Works of Pavement Alternatives 3.4.1.1 Site Clearance Up on the commencement of a certain road construction project, the primary work to be undertaken will be clearing of necessary site. In doing so, due attention shall be given to the road right of way, crushing & mixing plants and camp locations. The major tasks here are generally described as: Clear, grub, remove, and dispose of vegetation and debris within designated limits. Furthermore, if there are already built facilities, there may be a need to demolish them. According to AASHTO Specifications (2008), the major operations here are: dispose of material and debris and removal of low-hanging and unsound branches from remaining trees or shrubs. And when a given Agency pays for tree and stump removal on an individual unit basis, the Engineer will classify items removed according to the schedule of sizes designated in the contract. [3]
57 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
For further specifications, ERA Specifications (2002) provides certain set of possible works in addition to clearing and grubbing which result in increased cost. These are: removal and grabbing of large trees and tree stumps, re-clearing of surfaces, removal and storage of selected vegetation, demolition and removal, disposal or storage of existing structures, installations, road pavements, existing public utilities and hydraulic structures. [4] 3.4.1.2 Earthwork After site clearing procedure, earth works of the following and additional possible natures must be accounted for. Few are: removal of structures and obstructions, excavation and embankment, subgrade preparation, excavation and backfill for conduits and minor structures, erosion and sediment control, salvaging and placing top soil. (AASHTO, 2008) [3] In addition: protection of earthworks, finishing of slopes and stabilization may be considered for better estimation of works. (ERA, 2002) [4] 3.4.1.3 Sub base Works Few of the preliminary considerations include: material sources for sub-bases satisfying different requirements (crushed stone or recycled aggregate), proposed and/or economical set of equipments for the transportation and laying procedure, and protection as well as drainage provisions to be installed. [4] 3.4.1.4 Structures Different structures are required in addition to highway construction and they have great implications in the total estimated cost of a specific project. As of (AASHTO, 2008), different possible ones may be: temporary works, driven foundation piles, ground anchors, earth retaining systems, concrete and/or reinforced concrete structures, prestressed concrete, steel structures, stone masonry, timber structures, bearing devices, and slope protection. [3] 3.4.1.5 Drainage Provisions They may be: drains, culverts and appurtenance structures, curbing, channeling, open chutes, downpipes, concrete lining of open drains, pitching, stone work, and erosion protection. [4] One, two or a combination of these clearly has expenditure implications. 3.4.1.6 Miscellaneous and Ancillary Works They include: concrete for incidental construction, guard rail, fences, sidewalks, turf establishment, furnish and plant trees, shrubs, vines and ground covers, concrete barrier, erosion checks, reference markers, traffic control, erosion control mats and bales, and filter fabric. [3]
58 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
3.4.2 Base course and AC Works [For Flexible Pavements] 3.4.2.1 Base course When we think of Base Course construction, we shall consider the following in addition to labor and equipment. They are: subgrade modification, reconditioning existing base and surface, lime-treated courses, cement-treated base course, Portland or blended hydraulic cement concrete base course, lean concrete base course, lime-fly ash-treated courses, fly ash-treated course, open graded bituminous base (OGBB), open graded Portland cement concrete base (OGPCCB) and separator fabric for bases. [3] 3.4.2.2Asphalt Concrete For Asphalt Concrete works, apart from the extensive equipment demand, we shall assess materials like: Portland Cement, Asphalt Base Course, Mineral Filler, Fly Ash Subsection and Lime for Asphalt Mixtures. [3]
3.4.3 Cement Concrete Slab Works [For Rigid Pavements] Similar to the Asphalt Concrete counterpart, Portland Cement, Fine Aggregate, Coarse Aggregate, Load Transfer Devices, Joint Filler, Reinforcing Steel, Curing Materials, AirEntraining Admixtures, Chemical Admixtures, Fly Ash, Ground Granulated Blast Furnace, Slag (GGBFS), and Water. [3]
3.5 Programming For the purpose of our research, we have developed a software that accommodates the design procedures of AASHTO (Guide for Design of Pavement Structures, 1993) using the LISP Programming languages. Lisp is one of the oldest programming languages still in widespread use today. There have been many versions of Lisp, each sharing basic features but differing in detail. In this program we have used a version called Common Lisp, which is the most widely accepted standard. Lisp has been chosen here for three reasons. First, Lisp makes it easy to capture relevant generalizations in defining new objects. In particular, Lisp makes it easy to define new languages especially targeted at the problem at hand. This is apparently handy in AI applications, which often manipulate complex information that is most easily represented in some novel form. Lisp is one of the few languages that allows full flexibility in defining and manipulating programs as well as data. This feature was especially reflected in the modules that calculate various parameters such as the effective subgrade reaction, slab thickness and reinforcement schedule. Second, Lisp is one of the most widely used programming language in Artificial Intelligence programming. It is extremely good at manipulating language. This has been evident while designing the natural language user interface where a new embedded 59 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
programming language has been implemented for tackling the problem of language and semantic analysis. Third, Lisp includes a variety of inbuilt functions and paradigms of programming (such as object-oriented programming, functional programming and “program-as-data”) which makes it suitable to develop hybrid numerical, analytical and symbolic programs. This is reflected in the fact that we used: the Symbolic Paradigm for the AI macros, the Numerical and Object Oriented Paradigms for the interface and the analysis engine. [5]
60 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
References TO CHAPTER THREE [1] AASHTO, American Association of State Highway & Transportation Officials (1993), Guide for the Design of Pavement Structures, Capitol Street – Washington D.C., U.S.A. (Part I & II) [2] ERA, Ethiopian Road Authority (2002), Pavement Design Manual – Volume II, Addis Ababa, Ethiopia (Pp. 14 – 24) [3] AASHTO, American Association of State Highway & Transportation Officials (1993), Guide Specifications for Highways, Washington D.C., U.S.A. [4] ERA, Ethiopian Road Authority (2002), Standard Technical Specifications, Addis Ababa, Ethiopia [5] Norvig, Peter (1987), Paradigms of Artificial Intelligence Programming; Case Studies in Common Lisp, California, U.S.A.
61 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
CHAPTER FOUR RESEARCH DATA 4.1Acquired Secondary Data Table 4.1: Annual Average Daily Traffic of the paved Trunk Road from Adama (Nazareth) to Awash (Source: ERA, Annual Traffic Count Report, 2011) [1] 2009 AADT of the 125 km segment from Adama (Nazareth) to Awash No.
Vehicle Category
AADTi(No.)
Percent Composition (%)
1
Cars
352
10
2
Buses
670
18
3
Trucks
1066
29
4
Truck and Trailers
1584
43
Total AADT
3672
100
Table 4.2: Summary of Daily Traffic on ERA Network (1994–2004) (Source: AACC, Management of Commercial Road Transport in Ethiopia) [2] Annual Growth Rate in % 1994 - 2004
1999 - 2004
1999 – 2004
Cars
4.8
5.9
5.4
Buses
14.0
6.4
10.1
Trucks
5.6
7.2
6.4
Truck and Trailers
8.2
3.8
6.0
All Traffic
7.4
6.2
6.8
62 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 4.3: Traffic Growth Rate Considered in Re-alignment of Beseka Crossing (Source: Data of Core Consulting Engineers) [3] Year, Period
Passenger Vehicles (%)
Freight Vehicles (%)
2011 – 2020
5.0
8.0
2021 - 2027
4.0
6.0
Figure 4.1: Front Axle Load distribution of Buses [3]
Figure 4.2: Rear Axle Load distribution of Buses [3]
63 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Figure 4.3: Front Axle Load distribution of Trucks [3]
Figure 4.4: Rear Axle Load distribution of Trucks [3]
64 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Figure 4.5: Axle Load distribution of Truck Trailers (Articulated Type) [3]
Figure 4.6: Load Composition of Vehicles on the Design Lane [3]
65 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Figure 4.7: Nomenclature of Articulated Trucks (Source: Botswana Guideline for Axle Load Survey) [4] 66 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 4.4: Truck Factors based on actual Vehicles on the Design Lane (Use in combination with Figure 4.7 to understand the axle configuration) (Source: Consultancy Service for the Detailed Engineering Design for Realignment, Tender Document Preparation and Construction Supervision of Beseka Crossing (Metehara Railway Crossing – Awash Junction) Road Project, Ethiopian Roads Authority) [3] Truck Trailers (TT) 1.2+2.2 1.22+2.2 1.22+2.22 1.2-22 1.2-221 1.22-22 1.2-222 1.22-222 1.2-111
TF 7.92 13.238 15.025 3.442 3.191 8.3 0.57 20.437 2.343
Other Vehicles Small Bus (SB) Medium Bus (MB) Large Bus (LB) Medium Truck (MT) Heavy Truck (HT) (1.2) Heavy Truck (HT) (1.22)
TF 0.021 0.024 0.397 0.151 0.837 1.948
Table 4.5: Comparison of Truck Factors (Source: Consultancy Service for the Detailed Engineering Design for Beseka Crossing (Metehara Railway Crossing – Awash Junction) Road Project, Ethiopian Roads Authority) [3]
Projects/Survey
VehicleType
Consultants
Station
SB
MB
LB
MT
HT
TT 9.90
Modjo-Awash
Scott Wilson Kirkpatric
0.45
−
0.15
3.20
9.90
Modjo–Ziway
O’sulivan Grham
1.22
−
1.22
0.26
9.91
Mojoand Sembo
CORE JV AEC
0.04
−
1.40
2.84
8.52
19.92
Gore–Gambella
AEC
0.45
−
1.00
0.95
7.00
9.50
Nekemt–Bedele
Kocks JVMCE
0.30
−
1.51
0.33
3.66
10.43
Nekemt–Bedele
Gauff
0.27
−
1.14
0.84
6.17
8.89
Assossa-Kurmuk
CORE
0.12
−
0.86
0.23
3.63,5.23*
−
Nejo-Mendi
MCE
−
−
0.96
0.087
4.49,2.38*
7.44
Debretabor- Gobgob
CORE
−
1.29
2.96
0.29
6.82,9.43*
9.16 67
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
Wolkite- Hossaina
AAiT, SCEE
0.030 0.297 1.298 0.144 3.014,4.741* 0.324
CORE
0.031 0.344 0.741 0.061 0.591,0.432* 2.784 Besekalake bypass
CORE
0.021 0.024 0.397 0.151 0.837,1.948
**
For ERA and ** Kenyan PDM 0.021 0.024 0.397 0.151 3.0,4.74* catalogue Values ** IRC (Indian) 0.032 0.036 0.449 0.151 3,4.74* PDM catalogue Where SB stands for small bus, MB for medium bus, LB for large bus, MT for medium truck, HT for heavy truck and TT for truck and trailer Recommended
Table 4.6: Values of Truck Factors Employed (Source: Consultancy Service for the Detailed Engineering Design for Beseka Crossing (Metehara Railway Crossing – Awash Junction) Road Project, Ethiopian Roads Authority) Vehicle Type
TF on Awash to TF on Adama to Average Truck Factors Adama Lane Awash Lane for Addis Ababa Lane SmallBus 0.021 0.011 MediumBus 0.024 0.024 0.1473 LargeBus 0.397 0.256 MediumTruck 0.151 0.192 0.9787 HeavyTruck–1.2 0.837 0.395 HeavyTruck–1.22 1.948 0.856 Truck-Trailer1.2+2.2 7.920 0.382 Truck-Trailer1.22+2.2 13.238 2.088 Truck-Trailer1.22+2.22 15.025 3.182 10.349 Truck-Trailer1.2-22 3.442 0.261 Truck-Trailer1.22-22 9.192 0.724 Truck-Trailer1.2-221 3.191 0.230 Truck-Trailer1.22-222 20.437 2.241 Table 4.7: Summary of Test Results for Natural Gravel Course (Source: Consultancy Service for the Detailed Engineering Design for Beseka Crossing (Metehara Railway Crossing – Awash Junction) Road Project, Ethiopian Roads Authority) [3] Occurrence (%) 100
AASHTO Class’n A-1-b(0)
CBR (%) Swell (%) LL PI 81
0.17
NP NP
Remarks Suitable
68 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 4.8: Unit Rates of Pavement Structure Component Materials of Rigid Pavements and Flexible Pavements (Source: Construction Proxy.com and ERA Procurement Division) [5]
No. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 16. 17. 18. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. No. 1. 2. 3. 4. 5. 6.
I. Material Costs Item Name Cement Crushed Sand 01 Aggregate 02 Aggregate Admixture and Curing Chemical Timber Eucalyptus Nail Mould Oil Steel Deformed Bar Bitumen Bitumen for MC 30 Naphthalene Bitumen for RC 70 Kerosene Granular Subbase Crushed Base course II. Labor Cost General Foreman Gang Leader Daily Laborer Helper Concrete Plant Operator Carpenter Bar Bender Bitumen Distributor Operator Paver Operator Roller Operator III. Equipment Cost Item Name Hand Tools Concrete Vibrator Concrete Mixer Plant Paver Roller Bitumen Distributor
Cost per Unit 270 Birr/quintal 460 Birr/m3 368 Birr/m3 414 Birr/m3 12 Birr/liter 70 Birr/m2 2.0 Birr/ml 8.0 Birr/kg 2.00 Birr/liter 24.12 Birr/kg 34.50 Birr/kg 33.50 Birr/m2 17.91 Birr/liter 24.64 Birr/liter 16.80 Birr/liter 320 Birr/m3 394.4 Birr/m3 8000 Birr/month 5000 Birr/month 100 Birr/day 4000 Birr/month 5000 Birr/month 4000 Birr/month 4000 Birr/month 5000 Birr/month 10000 Birr/month 8500 Birr/month Cost per Unit 2.00 Birr/pc 42.36 Birr/hr 1200 Birr/hr 4000 Birr/hr 1000 Birr/hr 680 Birr/hr
69 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
4.2 Reasonably Justified Complementary Data Table 4.9: Factors to be used for estimation of AADT in the opening year and cumulative traffic at the end of design period (look at Section 5.2.2 to see detailed computation) Period Traffic Count to Road Opening Years 2009 to 2017 6.8 Traffic Growth (g in %) 8 No of Years in between (n) 1 Lane Distribution Factor (DL) Directional Distribution Factor 0.6 (DD) Period
Base Period 2017 to 2037 3.5 20 1
Remaining Design Period 2037 to 2057 2 20 1
0.6
0.6
Table 4.10: Values of design inputs used for the design of Rigid Pavement (see Section 5.5.2 to see how these values have been obtained) Parameter
Value
Reliability, R
95%
Overall Standard Deviate, So
0.35
Design Serviceability Loss, ΔPSI
2
Normal Standard Deviate, ZR
-1.645
Concrete Grade
C 35
Concrete Elastic Modulus, Ec
31.4 GPa (4.5 million psi)
Concrete Modulus of Rupture, Sc’
4.8 MPa (687.21 psi)
Load Transfer Coefficient, J
3.2
Drainage Coefficient, Cd
1.15
Steel Grade
S 400
Steel Working Stress, fs
260.83 MPa (37836 psi)
Friction Factor, F
1.5
70 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
REFERENCES TO CHAPTER FOUR [1]
ERA, Ethiopian Roads Authority (2011), Annual Traffic Count Report on the Federal Road Network in Ethiopia of 2009, Addis Ababa, Ethiopia (Pp. 9, 26 & 27)
[2]
AACC & Sectoral Associations (2009), The Management of Commercial Road Transport in Ethiopia, Addis Ababa Chamber of Commerce – Private Sector Development Hub, Addis Ababa, Ethiopia(Pp. 19 – 21)
[3]
Core Consulting Engineers (2011), Detail Engineering Design for the Re-alignment of Beseka Crossing (Metehara Railway Crossing – Awash Junction) Road Project for Ethiopian Roads Authority (ERA), Addis Ababa, Ethiopia
[4]
Roads Department, Botswana (2000), Guideline for Axle Load Surveys, ISBN 99912 0 - 358 – 3, Gaborone, Botswana (Pp. 26)
[5]
http://www.constructionproxy.com
71 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
CHAPTER FIVE ANALYSIS AND DISCUSSION 5.1 Introduction From research point of view, Analysis majorly contains the processing of collected data which may have been acquired on primary and/or secondary basis. Reasonably assumed parameters also play important roles in data processing. The analysis is expected to yield results and findings that serve as tools in justifying the objectives outlined at the very outset of the research. On the other hand Discussion involves clarifying, elaborating, entailing and shaping of raw Analysis results into comprehendible statements. Research findings derive their reliability from the set of collected data, analysis and interpretations of analysis results. In the meantime, one should keep in mind that different analysis methods and approaches may have adequate influence on data processing and could ultimately lead to potentially false conclusions. That is why for better acceptance of any research, considerable duration of time is dedicated to collecting precise data set and processing the collected data with the right analysis methods. Likewise at the end, this research aims at putting some ground forms for the general objectives set in Section 1.3, mainly, the implication of rigid pavement construction in Ethiopia from the case study picked for analysis. From the data set collected and presented in Chapter 4, Sections 4.1 and 4.2, the researchers have made extensive Analysis and Discussions on the segment from Adama (Nazareth) to Awash here in this Chapter. While checking ERA Pavement Design Manual, Volume II (2002) for assessing its proximity to the real scenario of behavior and response after construction of rigid pavement, one observes that it only considers two design requirements only: traffic and subgrade CBR. Even though, AASHTO, Guide for Design of Pavement Structures (1993) is a guide to be strictly followed in this research with its design considerations far more than traffic data and resilient modulus of roadbed, Section 5.4 is dedicated to deal with the design of the rigid pavement structure using ERA manual for the purpose of comparison with the forth coming AASHTO guide results. Section 5.5 contains the design of the rigid pavement structure using AASHTO Guide (1993). This is done for different subgrade CBR classes in the determined performance and service period and corresponds to its ERA counterpart. 72 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
For the case of flexible pavement, we have chosen to use the Indian Road Congress Design Manual-37, 2001 (IRC-37, 2001) because of its wide applicability and acceptance. Plus The IRC-37, 2001 results in economically cheaper pavements compared to other internationally recognized manuals and requires no chemically stabilized interlayer, thus making construction much easier. [1] Its geographic location and warm weather have more resemblance to Ethiopia more than other European codes. Implementing British and Indian Design Manuals is becoming increasingly common in Ethiopia because ERA Pavement Design Manual has provisions for only low numbers of equivalent million single axle loads (thirty million maximum). This shows that the manual has already turned obsolete since it no longer matches the traffic growth rate of the nation. Thus, the design manual needs to be reviewed and publicized as soon as possible. After the pavement alternatives have been designed for the same traffic and road bed (soil Sub grade) properties of different periods starting from base design period to service period, we shall make Unit Rate Analysis for each constituent as can be referred from Section 5.9. And having these unit values in mind, in addition to other considerations related to Life Cycle Cost Analysis (LCCA) discussed in Section 2.4, we progress towards Economical Analysis, Section 5.10. Generally in this chapter, the data that have been collected and reasonably assumed will be analyzed followed by discussions regarding analysis results in the following sections. The most important analysis results include traffic forecasting (involves design period, growth factor and historical traffic count data of the road segment), axle load survey interpretations, determining realistic equivalent million single standard axle loads and finally coming up with the proper flexible and rigid pavement designs.
5.2 Traffic Analysis 5.2.1 Design Period For the purpose of comparison, pavement alternatives shall be assessed for the same design periods to come up with the required justifications with regard to which one is preferable over the other. It is well explained in Section 2.5.4 that in order to be able to fairly compare the two alternatives (majorly of their life cycle costs), the discount rate and analysis period should be the same for both alternatives (FHWA, 2002). [2] Rigid pavements can be designed for a design period of 40 years or more (60 years being the limit) without any major maintenance (if properly designed and constructed) unlike flexible pavements (15 to 20 years, usually). [3] But for comparison, we shall design the two with the same design periods. To accommodate the two alternatives, let us pick the design period that readily suits flexible pavements. That is: according to ERA (Pavement Design Manual, Volume I, 2002) Table 2.1, 20 years is viable for Trunk and Link roads. [4] Since our segment 73 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
(Adama to Awash) is a Trunk Road according to ERA (Geometric Design Manual, 2002) Appendix A, Table A.2, we may proceed with our analysis. [5] However, the initial design period (base period) is always prone to adjustment since the number of equivalent single axle loads may be too large that there is no corresponding provision in the design manuals of many countries. In fact, this is exactly what we have encountered in our research. At first our theoretical base period was 20 years. But as can be seen from Table 5.19, the number of equivalent single axle loads at the 20th year is well beyond the provision of ERA and many other countries’ manuals. Therefore, we have adopted the Indian Road Congress (IRC) Design Manual-37, 2001 as explained in Section 5.1 From this base period value onwards, we shall consider stage construction through rehabilitation for the flexible pavement to reach the total service period of 40 years. Therefore, while the economy is assessed for initial investment (17 years design period) and stage constructions from this point in time to the 40th year of the flexible pavement construction, the rigid pavement shall be designed for equal periods, durations and service periods, to see a cost vs. time curve for the two counterparts in a single graph. This can be seen at the end of this Chapter. But what should be recalled is that rigid pavements can be designed for 40 years without the need for major maintenance at intervals.
5.2.2Traffic Volume As discussed briefly in Chapter 4, the traffic count data of Ethiopian Roads Authority (ERA) report is analyzed here under. According to the report of ERA (Annual Traffic Count Report on the Federal Road Network in Ethiopia of 2009, February 2011), four categories of vehicles were assessed. [6] Table 5.1 indicates the Annual Average Daily Traffic (AADT) and percent composition of each category. Table 5.1: Annual Average Daily Traffic of the paved Trunk Road from Adama (Nazareth) to Awash (Source: ERA, Annual Traffic Count Report, 2011) 2009 AADT of the 125 km segment from Adama (Nazareth) to Awash No.
Vehicle Category
AADTi(No.)
Percent Composition (%)
1
Cars
352
10
2
Buses
670
18
3
Trucks
1066
29
4
Truck and Trailers
1584
43
Total AADT
3672
100 74
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
According to ERA Pavement Design Manual 2002 Volume I, determining the cumulative number of vehicles over the design period of the road involves the following steps: 1. 2. 3. 4.
Determine the initial traffic volume, AADT i, t = 0 for each vehicle category Estimate the annual growth rate, g expressed as a decimal fraction, The anticipated number of years, n between the traffic survey and road opening, Determine AADT i, t = n , the traffic volume in both directions on opening year by: AADT i, t = n = AADT i, t = 0 * (1 + g) n . . . . . . . . (5.1) 5. The cumulative number of vehicles, T i, t = n over a design period n years is: T i, t(n) = 365 * AADT i, t = 0 * [
(𝟏 + 𝐠)𝐧 – 𝟏 g
] . . . . . . . . . (5.2)
For design, the cumulative number of vehicles for each category is required from the traffic opening date to the end of the design period. In such instances, the future traffic shall be obtained by forecasting with the employment of traffic growth, g. And to obtain the cumulative traffic in the design lane, the directional and lane distribution factors shall be obtained or assumed. 5.2.2.1 Traffic Growth, g As the traffic count report of ERA (Annual Rural Traffic Movement In Ethiopia of 2008, may 2009) indicates, the 2008 AADT for the four categories of vehicles was: Cars – 260, Buses – 371, Trucks – 803 and Trucks & Trailers – 1007, with Total AADT of 2441. [7] But as compared to the 2009 AADT of ERA (Annual Traffic Count Report on the Federal Road Network in Ethiopia of 2009, February 2011), the annual traffic increased by 50 percent (that is, the annual traffic 305,125 vehicles/year (2008) to 459,001 vehicles/year (2009)). But the total average increment of traffic on the road network of Ethiopia has shown to be 10 % for Asphalt surfaced roads and 3% for gravel roads. [6] But for this research, we will not directly use the increment that was attained during 2008-2009 for two major reasons. One is: since the time was the Ethiopian Millennium, the 2009 traffic to the port might have increased dramatically. And second: the future prospects of railway infrastructure may severely divert/lower the traffic exhibited in this segment. These reasons in addition to other unforeseen ones call the need to seek another appropriate growth factor. Besides, using 50% growth rate completely contradicts the historical traffic count of the segment Adama-Awash as will be explained in the following paragraph. According to the research carried out by Addis Ababa Chamber of Commerce (AACC) on (The Management of Commercial Road Transport in Ethiopia, 2009), it was assessed that the growth in daily traffic (in Vehicle-Km) on ERA Network for 10 years from 1994 to 2004 was as follows : [8]
75 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.2: Summary of Daily Traffic on ERA Network (1994–2004) (Source: AACC, Management of Commercial Road Transport in Ethiopia) Annual Growth Rate in % 1994 - 2004
1999 - 2004
1999 – 2004
Cars
4.8
5.9
5.4
Buses
14.0
6.4
10.1
Trucks
5.6
7.2
6.4
Truck and Trailers
8.2
3.8
6.0
All Traffic
7.4
6.2
6.8
Having this data and putting it into consideration, we may reasonably assume an averaged traffic growth for the design period for the segment from Adama (Nazareth) to Awash in two phases. The first phase to be the years from 2009 to 2017 (the assumed opening date of the roadway and keeping in mind that the Addis Ababa-Djibouti railway will begin service in 2016), a traffic growth value of 6.8 % per annum can be taken. For the second phase, i.e. 2018 to 2037 (end of base period), we may assume a traffic growth of 3.5 % per Annum (rather than 6.8 % per annum). This is because future prospects with regard to 1. Infrastructure development & improvement of the road network: These contain the Link Roads that are set in the current (2010 to 2015) and the coming (2016 to 2020) GTP, 2. Rail transportation: It is under construction by Ethiopian Railway Corporation (ERC) and is to be completed at the end of 2015 or the beginning of 2016 (before the proposed opening date of the roadway from Adama to Awash of this research) which serves to transport freight and passengers to and from Djibouti port and 3. New Port Prospects: the researchers of this study have added this point with no so called detail reviewed strategy of such prospects. But Ethiopia plans to build ports in Somalia and Kenya in cooperation of different nations of the Horn of Africa. These prospects will be very crucial in the diversion of considerable amount of traffic from this corridor. In this manner, this research intends to be realistic towards to the scenarios that will happen. In further search for facts that firmly justify the above growth rates, g1 and g2 (for the periods 2009 to 2017 and 2017 to 2037, respectively), this research tried to assess similar investigation conducted in the area and has indeed come across points that are reliable to their counterpart results. 76 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
According to the Design, Consultancy and Supervision service of Core Consulting Engineers Plc., August 2011 to the Ethiopian Roads Authority under the title Detail Engineering Design for the Re-alignment of Beseka Crossing (Metehara Railway Crossing – Awash Junction) Road Project, stage values of traffic growth values were assumed. Table 5.3 clearly labels the growth rates of the consulting firm: [9] Table 5.3: Traffic Growth Rate Considered in Re-alignment of Beseka Crossing (Source: Data of Core Consulting Engineers) Year, Period
Passenger Vehicles (%)
Freight Vehicles (%)
2011 – 2020
5.0
8.0
2021 - 2027
4.0
6.0
Therefore for the two distinct periods, i.e. from 2009 to 2017 and 2017 to 2037, it is justifiable and reliable to proceed with the original growth rates of 6.8 % and 3.5 %, respectively for the whole traffic count. 5.2.2.2 Directional Distribution Factor, DD Since the segment is part of the import – export corridor of the nation, we shall be very careful to include the effect of fully loaded truck and truck – trailer axle loads on the pavement structure. This implies greater emphasis will be given to the direction from Awash to Adama, i.e. the design direction. Therefore, a reasonable value of DD = 0.6 may be assumed to account for the above case. For further justification, as the traffic count data of (Core Consulting Engineers Plc., August 2011); in 2011, the total AADT on the Addis Ababa lane (Addis Ababa direction) was 1839 while that on the Dire Dawa lane (Dire Dawa Direction) was 1703. This yields a percentage of 52% on the Addis Ababa lane to be 52 %. [9] Therefore, we may validate the value of DD which is 0.6. 5.2.2.3 Lane Distribution Factor, DL Since the roadway segment is a rural road, it may be practical to assume it to be a two lane – two way trunk rural roadway. Therefore, a lane distribution factor of 100 percent (DL = 1) shall be taken for calculation. Finally, the total traffic volume in the opening year and cumulative number of vehicles of each category expected during the base period of the segment can be easily found out (refer Tables 5.4 and 5.5).
77 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.4: Factors to be used for estimation of AADT in the opening year and cumulative traffic at the end of design period
Period Years Traffic Growth (g in %) No of Years in between (n) Lane Distribution Factor (DL) Directional Distribution Factor (DD)
Period from Traffic data Count to Road Opening
Base Period
Remaining Design Period
2009 to 2017 6.8 8 1
2017 to 2037 3.5 20 1
2037 to 2057 2 20 1
0.6
0.6
0.6
5.2.2.4 Determination of Annual Average Daily Traffic and Cumulative Number of Traffic Briefly speaking, the following steps shall be followed to compute future annual daily traffic and cumulative number of traffic throughout the base period. (i) Identify the vehicle category series of the traffic count in 2009 (ERA, 2011) (ii) Take the base traffic count report in 2009 for each category of vehicle (ERA, 2011) (iii) The AADT of each vehicle category in 2017 (the year the roadway is opened for operation) and recalling from Section 2.3.1.2, it is calculated as: AADT i, t = n = AADT i, t = 0 * (1 + g) n . . . . . . . . . (5.3) (iv) Calculate the AADT of each vehicle category in one direction in the design lane for 2017 (starting year of roadway operation) and recalling from Section 2.3.1.2, it is calculated as: AADT i, design, t = n = DL * DD * AADT i, t = 0 * (1 + g) n . . . . . . . . . (5.4) (v) Determine the cumulative number of vehicles in their respective category from the year 2017 to 2037 (the design/base period) and recalling from Section 2.3.1.2, it is calculated as: Cum. Traffic i, for n = 20 years = 365 * DL * DD * AADT i, t = 0 * [
(𝟏 + 𝐠)𝐧 – 𝟏 g
] . . . (5.5)
78 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.5: Estimation of AADT in the opening year and cumulative traffic at the end of the design period (i)
(ii)
(iii)
Vehicle Category
AADTi in 2009
AADTi in 2017
Cars Buses Trucks Truck - Trailers Total
352 670 1066 1584 3672
595.8167182 1134.082958 1804.376766 2681.175232 6215.451674
(iv)
(v)
AADTi in 2017 (in Cumulative Vehicle one direction in the Volume in the Design design lane) Period (from 2017 to 2037) 357.4900309 3690042.079 680.4497747 7023659.638 1082.626059 11174956.98 1608.705139 16605189.35 3729.271004 38493848.05
The following tables (Tables 5.6 to 5.9) illustrate the increment in cumulative traffic every year. Table 5.6: AADT and Cumulative number of cars exhibited on the segment during the base period Year
Car AADT
2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029
352 375.936 401.499648 428.8016241 457.9601345 489.1014236 522.3603205 557.8808222 595.8167182 616.6703033 638.2537639 660.5926456 683.7133882 707.6433568 732.4108743 758.0452549 784.5768388 812.0370282 840.4583242 869.8743655 900.3199683
One directional AADT 211.2 225.5616 240.8997888 257.2809744 274.7760807 293.4608542 313.4161923 334.7284933 357.4900309 370.002182 382.9522583 396.3555874 410.2280329 424.5860141 439.4465246 454.827153 470.7461033 487.2222169 504.2749945 521.9246193 540.191981
Cumulative Cars per Year
130483.8613 265534.6577 405312.232 549982.0214 699715.2534 854689.1486 1015087.13 1181099.041 1352921.369 1530757.478 1714817.851 1905320.337 79
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
2030 2031 2032 2033 2034 2035 2036 2037
931.8311672 964.4452581 998.2008421 1033.137872 1069.297697 1106.723116 1145.458426 1185.54947
AAiT, SCEE
559.0987003 578.6671548 598.9205053 619.8827229 641.5786183 664.0338699 687.2750553 711.3296823
2102490.41 2306561.435 2517774.947 2736380.931 2962638.125 3196814.321 3439186.683 3690042.079
Table 5.7: AADT and Cumulative number of Buses exhibited on the segment during the base period Year
Bus AADT
2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037
670 715.56 764.21808 816.1849094 871.6854833 930.9600961 994.2653827 1061.875429 1134.082958 1173.775861 1214.858017 1257.378047 1301.386279 1346.934799 1394.077516 1442.87023 1493.370688 1545.638662 1599.736015 1655.726775 1713.677212 1773.655915 1835.733872 1899.984557 1966.484017 2035.310958 2106.546841 2180.27598 2256.58564
One directional Cumulative AADT Buses per Year 402 429.336 458.530848 489.7109457 523.01129 558.5760577 596.5592296 637.1252572 680.4497747 704.2655168 248364.1678 728.9148099 505421.0814 754.4268283 771474.987 780.8317673 1046840.779 808.1608791 1331844.374 836.4465099 1626823.095 865.7221377 1932126.071 896.0224125 2248114.652 927.383197 2575162.832 959.8416089 2913657.699 993.4360652 3263999.886 1028.206327 3626604.05 1064.193549 4001899.36 1101.440323 4390330.005 1139.990734 4792355.723 1179.89041 5208452.341 1221.186575 5639112.341 1263.928105 6084845.44 1308.165588 6546179.199 1353.951384 7023659.638
80 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.8: AADT and Cumulative number of Trucks exhibited on the segment during the base period Year
One directional Cumulative AADT Trucks per Year 2009 1066 639.6 2010 1138.488 683.0928 2011 1215.905184 729.5431104 2012 1298.586737 779.1520419 2013 1386.890635 832.1343808 2014 1481.199198 888.7195186 2015 1581.920743 949.1524459 2016 1689.491354 1013.694812 2017 1804.376766 1082.626059 2018 1867.529953 1120.517972 395158.5117 2019 1932.893501 1159.736101 804147.5713 2020 2000.544773 1200.326864 1227451.248 2021 2070.563841 1242.338304 1665570.553 2022 2143.033575 1285.820145 2119024.034 2023 2218.03975 1330.82385 2588348.387 2024 2295.671141 1377.402685 3074099.093 2025 2376.019631 1425.611779 3576851.073 2026 2459.180318 1475.508191 4097199.372 2027 2545.25163 1527.150978 4635759.862 2028 2634.335437 1580.601262 5193169.968 2029 2726.537177 1635.922306 5770089.429 2030 2821.965978 1693.179587 6367201.071 2031 2920.734787 1752.440872 6985211.62 2032 3022.960505 1813.776303 7624852.538 2033 3128.764122 1877.258473 8286880.889 2034 3238.270867 1942.96252 8972080.232 2035 3351.610347 2010.966208 9681261.552 2036 3468.916709 2081.350026 10415264.22 2037 3590.328794 2154.197276 11174956.98 Table 5.9: AADT and Cumulative number of Articulated Trucks exhibited on the segment during the base period Year 2009 2010 2011 2012 2013 2014
Truck AADT
Truck and One directional Cumulative Truck Trailer AADT AADT and Trailers per Year 1584 950.4 1691.712 1015.0272 1806.748416 1084.04905 1929.607308 1157.764385 2060.820605 1236.492363 2200.956406 1320.573844 81
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037
2350.621442 2510.4637 2681.175232 2775.016365 2872.141938 2972.666905 3076.710247 3184.395106 3295.848934 3411.203647 3530.595775 3654.166627 3782.062459 3914.434645 4051.439857 4193.240253 4340.003661 4491.903789 4649.120422 4811.839637 4980.254024 5154.562915 5334.972617
1410.372865 1506.27822 1608.705139 1665.009819 1723.285163 1783.600143 1846.026148 1910.637063 1977.509361 2046.722188 2118.357465 2192.499976 2269.237475 2348.660787 2430.863914 2515.944152 2604.002197 2695.142274 2789.472253 2887.103782 2988.152415 3092.737749 3200.98357
AAiT, SCEE
587177.3757 1194905.96 1823905.044 2474919.096 3148718.64 3846101.169 4567892.085 5314945.684 6088146.159 6888408.65 7716680.328 8573941.516 9461206.844 10379526.46 11329987.26 12313714.19 13331871.56 14385664.44 15476340.08 16605189.35
5.2.2.5 Axle Loads Axle Load Surveys are conducted to estimate the axle loads of different moving vehicles on some location of particular interest to come up with representative values of axle loads for each category of vehicles according to the provisions of a certain chosen manual. Based on this, most countries have regulations on the size and weight of vehicles to ensure road safety and to contain the weight of vehicles within the carrying capacity of the pavement structure. As stated in Section 2.4.2 of ERA Pavement Design Manual, Volume I (2002), developing countries like Ethiopia have their vehicles grossly overloaded (as much as 60 percent higher than the permitted regulation). In such cases, a pavement design which assumes that the vehicles would be conforming to the country’s regulations on vehicle weight and axle loading is bound to fail. Hence, it should consider factors like: Overloaded vehicles using the road and ability to undertake effective road maintenance on case by case basis. For the design to serve its purpose regarding this, the types of construction must be: robust, capable of carrying heavy loads and able to withstand traffic to some level without certain routine and periodic maintenance procedures. [4] The practice of vehicle axle load survey remained quite poor up until 2002. But from 2002 to present, individual projects have begun relying on their own axle load survey 82 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
data. Since these surveys are for a limited time period, they may not give a truly representative data for other researches like this one. Thus, it is possible to say that the most arguable part of this thesis happens to be truck factors which are to be determined from vehicle axle load survey. We were unable to recover the exact vehicle type (car, buses, trucks and articulated trucks) and their respective axle configuration (single, tandem, tridem) along with axle loads despite making repeated efforts. This could be partly attributed to the fact that vehicle axle load survey is still in its infant stage in the nation let alone the disclosure of such data. However, we did acquire a processed axle load survey data of (Core Consulting Engineers Plc., August 2011), Detail Engineering Design for the Re-alignment of Beseka Crossing (Metehara Railway Crossing – Awash Junction) Road Project (see Figure 5.1). Despite this limited success, another shortcoming is the fact that the traffic count recovered from ERA’s archive is based on only definitive vehicle types, i.e. cars, buses, trucks and articulated trucks. A better estimation could have been reached if different categories such as: mini buses, medium buses, large buses, medium trucks, heavy trucks and differing articulated tucks such as those displayed in Figure 5.2 were separately counted. [9] This is so because the available axle load survey was conducted for such detailed vehicle groups. The researchers of this paper decided to further adjust this processed data to suit the thesis better for two major reasons: 1. It represents the exact site (road segment) chosen for this research 2. It represents the axle loads of heavily loaded, lightly loaded and empty vehicles that commonly exist in Ethiopia
83 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Figure 5.1: Map depicting the Road Segment (Source: Google Earth)
84 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Figure 5.2: Nomenclature of Articulated Trucks (Source: Botswana Guideline for Axle Load Survey) [10] BSc. Thesis
85
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.10: Front and Rear Axle Load Distribution of Different Vehicle Categories with their Percentage Probability of Occurrence Measured in Re-alignment of Beseka Crossing (Source: Data of Core Consulting Engineers)
Vehicle Category Designation Small Axle Type Front Rear 1.5 (ton) --2.5 (ton) 42 -3.5 58 25 4.5 -34 5.5 -34 6.5 -7 7.5 --8.5 --9.5 --10.5 --11.5 --12.5 --13.5 --14.5 --15.5 --16.5 --17.5 ---
Buses Middle Front Rear --50 -50 17 -33 -33 -17 -----------------------
Large Front Rear --8 -50 25 16 25 25 8 -33 -8 ---------------------
Trucks Articulated Trucks Medium Heavy Truck - Trailer Front Rear Front Rear Axle 1 Axle 2 Axle 3 Axle 4 Axle 5 28 16.5 -------41 17.5 -------16 18 31 24 1 1 1 1 1 11 15 21 7 2 3 3 1 2 4 4 14 7 6 4 6 4 7 -9 34 10 18 10 10 8 9 -7.5 -21 29 12 17 10 13 -4 -10 25 16 15 12 9 -7.5 -14 13 12 13 12 13 ---2 6 14 8 13 10 ---5 1 9 9 11 9 -----5 7 7 8 -----7 5 9 8 -----4 3 3 4 -----2 2 3 3 -----1 -3 2 -------2 1
Axle 6 --2 3 7 10 11 11 17 8 10 7 6 4 2 2 1
86 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
The survey was carried out using mobile weigh bridge model number Intercom model LP 600. It was conducted at the entry of Metehara town from Addis Ababa for four days from 6am to 6pm (two days for each lane) back in 2011. During the survey, each axle of the commercial vehicles on both directions was weighed and load was recorded. Please note that Table 5.10 illustrates average axle load. For example 3.5 tons represents the range between 3 tons and 4 tons. For exact count, please refer Chapter 4. We can easily reason out why there is such a considerable degree of variation in loads for almost all the vehicle types, i.e. buses, trucks and trucks and trailers. It is because some travel empty, others partially loaded and still others fully loaded. (See Figure 5.3) The survey result is also summarized in the following table. Table 5.11: Traffic Survey Result Acquired in the Re-alignment of Beseka Crossing (Source: Data of Core Consulting Engineers) Vehicle Category
Front Axle (tons)
Rear Axle (tons)
Small Buses
1.3 to 3
1.4 to 4
Medium Buses
1.3 to 3
1.5 to 4.5
Large Buses
3 to 6
3 to 7.5
Medium Trucks
1.5 to 5
2 to 10
Heavy Trucks
3.5 to 7
5 to 12
Truck Trailers (Varying depending on freight material type)
5 to 8.5
6 to 16
Figure 5.3: Load Composition of Vehicles on the Design Lane Measured in Realignment of Beseka Crossing (Source: Data of Core Consulting Engineers) 87 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
5.2.2.6 Determination of Truck Factors The Truck Factor is equal to the summation of Equivalency Factors of each axles of a vehicle. Thus, it is apparent that the accurate determination of equivalent axle load factors is very important. We were unable to recover exact vehicle types (car, buses, trucks and articulated trucks) using the segment and their respective axle configuration (single, tandem, tridem) along with their axle loads despite making repeated efforts as explained in Section 5.2.2.5. For this reason, it was necessary to partly rely on the processed truck factor employed in the Besseka realignment design. With this regard, the following facts have been taken into consideration to carefully adopt the processed data. 1. Tandem and Tridem Axles have comparatively less pavement damage than successive single axles of equal load magnitude (in which underestimation is the risk in scenarios where little data is available as such), 2. Overloading of commercial vehicles is the case (even up to 60 % more than the fully loaded state according to ERA (2002)), 3. Variation of axle configurations to a wider range ( up to 9 among Truck-Trailers) The equivalence factors, determined by Equation 5.6 conform to the ERA, Kenyan and many more Pavement Design Manuals. EF = (Wtx/80) 4.5 . . . . . . . . . .. (5.6) Where: Wtx- the axle load determined from field test in KN (Axle Load Survey). TF = ∑ni=1 EF. . . . . . . . . .. (5.7) Where, EF = Equivalence Factor, AL = Axle Load, TF = Truck Factor, n = the number of axles of the vehicle. Please note here that the following truck factors are only processed data acquired from consultancy to ERA. The mean equivalence factor was determined by taking the mean value of equivalence factor of corresponding axles of each vehicle class and the results were summed to get Truck Factors. Since the actual vehicle types (axle configuration) and the corresponding loads were not made available to us despite our repeated efforts, we have no means of cross checking. However, we believe that the results were interpreted by experienced professionals and thus we feel confident that they can be used for further investigation. For the subject project axle load analysis was made on directional basis i.e. truck factor of vehicle classes on each direction was determined separately. Presented here is the truck factor of the design lane (Awash to Adama).
88 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.12: Truck Factors based on actual Vehicles on the Design Lane (Use in combination with Figure 5.2 to understand the axle configuration)(Source: Core Consulting Engineers, Detailed Engineering Design for Realignment of Beseka Crossing) Truck Trailers (TT) 1.2+2.2 1.22+2.2 1.22+2.22 1.2-22 1.2-221 1.22-22 1.2-222 1.22-222 1.2-111
TF 7.92 13.238 15.025 3.442 3.191 8.3 0.57 20.437 2.343
Other Vehicles Small Bus (SB) Medium Bus (MB) Large Bus (LB) Medium Truck (MT) Heavy Truck (HT) (1.2) Heavy Truck (HT) (1.22)
TF 0.021 0.024 0.397 0.151 0.837 1.948
Having this result at hand, the design professionals at Core Consulting decided to check with the values employed for other projects carried out in the country as the following table illustrates: Table 5.13: Comparison of Truck Factors of Different Road Projects (Source: Core Consulting Engineers, Detailed Engineering Design for Realignment of Beseka Crossing)
Projects/Survey
Vehicle Type Consultants
Station
SB
MB
LB
MT
HT
TT 9.90
Modjo - Awash
Scott Wilson Kirk patric
0.45
−
0.15
3.20
9.90
Modjo – Ziway
O’sulivan Grham
1.22
−
1.22
0.26
9.91
Mojo and Sembo
CORE JV AEC
0.04
−
1.40
2.84
8.52
19.92
Gore – Gambella
AEC
0.45
−
1.00
0.95
7.00
9.50
Nekemt – Bedele
Kocks JV MCE
0.30
−
1.51
0.33
3.66
10.43
Nekemt – Bedele Assossa - Kurmuk
Gauff CORE
0.27 0.12
− −
1.14 0.86
0.84 0.23
6.17 3.63,5.23*
8.89 −
Nejo - Mendi
MCE
−
−
0.96
0.087
4.49,2.38*
7.44
Debretabor - Gobgob
CORE
−
1.29
2.96
0.29
6.82,9.43*
9.16
Wolkite - Hossaina
CORE
Besekalake bypass
0.030 0.297 1.298 0.144 3.014,4.741* 0.324
CORE
0.031 0.344 0.741 0.061 0.591,0.432* 2.784 **
0.021 0.024 0.397 0.151 0.837,1.948
89 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
Recommended
AAiT, SCEE
For ERA, Kenya Catalogue 0.021 0.024 0.397 0.151
IRC (Indian)PD 0.032 0.036 0.449 0.151 M catalogue * Truck factor of heavy trucks with axle configuration of 1.22
Values
3.0,4.74*
**
3,4.74*
**
** Very many articulated types were encountered (Refer Table 2.10) After evaluating the data contained in Table 5.13 and making some changes, the designers finally came up with truck factors that are indicated in the following table. Table 5.14: Values of Truck Factors Employed(Source: Core Consulting Engineers, Detailed Engineering Design for Realignment of Beseka Crossing) Vehicle Type
SmallBus MediumBus LargeBus MediumTruck HeavyTruck–1.2 HeavyTruck–1.22 Truck-Trailer1.2+2.2 Truck-Trailer1.22+2.2 Truck-Trailer1.22+2.22 Truck-Trailer1.2-22 Truck-Trailer1.22-22 Truck-Trailer1.2-221 Truck-Trailer1.22-222
TF on Awash to TF on Adama to Average Truck Factors Adama Lane Awash Lane for Addis Ababa Lane 0.021 0.024 0.397 0.151 0.837 1.948 7.920 13.238 15.025 3.442 9.192 3.191 20.437
0.011 0.024 0.256 0.192 0.395 0.856 0.382 2.088 3.182 0.261 0.724 0.230 2.241
0.1473*
0.9787*
10.349*
* We conservatively take the value of design lane truck factor (which is almost 10 folds of the other lane) due to two major reasons: 1. To avoid the current roadway failures of the existing road on this lane 2. Since it is recommended in ERA manual that, for a country like Ethiopia, overloading beyond the fully loaded state could be the norm As can be noted from Table 5.14, different values of truck factors correspond to different kinds of vehicles with different axle configuration and loading condition. Remember that for each category, a mean value of equivalency factor is used, that is to say that ten small buses, for example, may be weighed and the equivalency factor for each axle of each small bus shall be computed and an average value of equivalency factor for each axle shall be determined. Finally the mean values of each axle should be summed up to find out the relative damage that could be done to the pavement by all axles of the vehicle category, i.e. small bus in this particular case. 90 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
For the sake of this research, we have come up with a way of using these truck factors that have actually been determined by experienced professionals through site vehicle survey for rigid pavements. One strong advantage on our side is the fact that these values really do exist on the selected road segment. Therefore, it is safe to say that the computation of truck factors is virtually free from assumptions that may lead to wrong design million equivalent single axles (msa). This is extremely crucial because, for both flexible and rigid pavements, the msa (along with subgrade strength) is the sole decider of pavement layer thicknesses. It is also apparent that most of the damage that will be done to the pavement comes from truck-trailer types 1.22-222, 1.22+2.22, 1.22+2.2 and 1.22-22. However, it is not clear what percentage these articulated truck types contribute to the overall truck-trailer family from the traffic count of ERA. Dedicating a great percentage of the truck-trailer vehicle type to these axle configurations will definitely result in an unrealistically huge MSA and relatively thick pavement layers. In the mean time, we should not give them an unfairly small portion. That will underestimate the damage that could be imposed on the pavement by these axle configurations. Therefore we shall find a harmonious approach between the two extremes. Obtaining Truck Factors for Rigid Pavements As different manuals recommend, the truck factors for rigid pavements is less than that of flexible pavements for higher axle loads greater than the standard axle. This is because of the relative less sensitivity of rigid pavements to higher loads compared to their flexible pavement counterpart. In this section, let us give emphasis to the ERA, Pavement Design Manual, Volume II (2002), for comparison of the equivalency factor of the two counterparts. We may refer Table 5.15 Table 5.15: Comparison of Flexible and Rigid Pavement Equivalency Factors of ERA (i) (ii) Axle Load ('000 kg) Flexible (n = 4.5) 3 0.011 4 0.040 5 0.111 6 0.251 7 0.503 8 0.917 9 1.559 10 2.504 11 3.845 12 5.688 13 8.154
(iii) Flexible (n = 4) 0.018 0.0579 0.141 0.293 0.543 0.926 1.484 2.261 3.310 4.689 6.458
(iv) Rigid 0.02 0.05 0.13 0.28 0.53 0.93 1.53 2.4 3.63 5.25 7.33
(v) Ratio (to n = 4.5) 1.80 1.233 1.175 1.114 1.054 1.014 0.982 0.958 0.944 0.923 0.899 91
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
14 11.382 8.686 15 15.524 11.447 16 20.756 14.818 17 27.266 18.885 18 35.264 23.736 19 44.978 29.466 20 56.655 36.177 (i) ERA’s recommendation (that is 4.5 power) given by:
AAiT, SCEE
9.92 13.1 17 21.6 27.1 33.7 41.4
0.872 0.844 0.819 0.792 0.769 0.7491 0.731
EF = (Wt/ 80) 4.5 . . . (5.8) (ii) AASHTO’s recommendation (that is 4 power) given by: EF = (Wt/ 80) 4. . . (5.9) (iii) Ratio of Equivalency Factors; Ratio = EF Rigid / EF of Power 4.5. . . (5.10) We may also inspect the relative difference of the two from Figure 5.4 and 5.5 (of ERA’s provision) and Figures 5.6 and 5.7 (AASHTO’s provision) The intent of the above procedure is to directly draw a relationship between the truck factors of rigid pavements and flexible pavements. This is rarely done because under normal circumstances where vehicle axle configurations along with axle loads are available, the usual practice is to determine equivalency factors by using equivalency factors provided in different manuals. However, as stated in Section 5.2.2.4, we couldn’t recover such data. Therefore the only option we have is to observe a pattern between rigid and flexible equivalency factors and directly pull out an estimate of the truck factor and thus, number of standard equivalent single axles for the rigid pavement.
92 BSc. Thesis
Equivalency Factor, EF
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
60 56 52 48 44 40 36 32 28 24 20 16 12 8 4 0
AAiT, SCEE
Flexible (n = 4.5) Flexible (n = 4) Rigid
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 Axle Load in '000 kg
Ratio (EF Rigid / EF Flex. n = 4.5)
Figure 5.4: Plot of the Equivalency Factors of Flexible & Rigid Pavements Vs. their Respective Axle Loads (ERA, 2002) 1.9 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.1 1 0.9 0.8 0.7 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Axle Load Figure 5.5: Plot of the Ratio of Equivalency Factors Rigid & Flexible Pavements Vs. Axle Loads (ERA, 2002)
93 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.16: Comparison of Flexible and Rigid Pavement Equivalency Factors of AASHTO [12, 13] Axle Load (kip) 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
Axle Load (KN) 8.9 17.8 26.7 35.6 44.5 53.4 62.3 71.2 80.1 89 97.9 106.8 115.7 124.6 133.5 142.4 151.3 160.2 169.1 178 186.9 195.8 204.7 213.6 222.5
EF for Flexible Pavements 0.0002 0.002 0.01 0.032 0.082 0.176 0.341 0.604 1 1.57 2.34 3.36 4.67 6.29 8.28 10.7 13.6 17.1 21.3 26.3 32.2 39.2 47.3 56.8 67.8
EF for Rigid Ratio of EF of Rigid Pavements to Pavements Flexible Pavements 0.00018 0.9 0.00209 1.045 0.01043 1.043 0.0343 1.071875 0.0877 1.069512 0.189 1.073864 0.36 1.055718 0.623 1.031457 1 1 1.51 0.961783 2.18 0.931624 3.03 0.901786 4.09 0.875803 5.39 0.856916 6.97 0.841787 8.88 0.829907 11.18 0.822059 13.93 0.81462 17.2 0.807512 21.08 0.801521 25.64 0.796273 31 0.790816 37.24 0.787315 44.5 0.783451 52.88 0.779941
94 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
80 Flexible
Equivalency Factors, EF of n = 4
70
Rigid 60
50 40 30 20 10 0 0
20
40
60
80
100 120 140 160 180 200 220 240 Axle Load, KN
Ratio = EF Rigid/Flexible
Figure 5.6: Plot of the Equivalency Factors of Flexible & Rigid Pavements Vs. their Respective Axle Loads (AASHTO, 1993) 1.2 1.1 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0
20
40
60
80
100 120 140 160 180 200 220 240 Axle Load in KN
Figure 5.7: Plot of the Ratio of Equivalency Factors Rigid & Flexible Pavements Vs. Axle Loads (AASHTO, 1993) 95 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
5.2.2.7 Cumulative Equivalent Standard Axles To find the Equivalent Standard Axles in millions (esa), we multiply the Truck Factors by the cumulative traffic count of each category at the end of base period (with certain correction for simulating Rigid Pavement scenarios regarding response to heavy traffic loads) as presented in the following table. Cumulative Equivalent Standard Axles for Rigid Pavement Design Table 5.17: Cumulative Standard Axles of the Roadway at the 20th year Base Period of Rigid Pavements (i) Vehicle Category
(ii) Cumulative Vehicle
(iii) Truck Factor
(iv) (v) Correction for Rigid Cumulative Pavements Performance Standard Axles
Cars
3690042.079
0
1
0
Buses
7023659.638
0.1473
1
1034585.065
Trucks
11174956.98
0.9787
1
10936930.4
Truck - Trailers
16605189.35
10.349
0.95*
163254749.4
38493848.05 175 226 264.8 * Correction Factor for an axle load greater than the standard axle, interpolated from Table 5.11(ERA) and Table 5.12 (AASHTO) for EF average of Truck-Trailers. TF = 10.349 (That is: for 6 axles, EF avg = 1.725) and was found to be 0.95 for both ERA and AASHTO. Therefore, the cumulative Million Equivalent Standard Axles = 175 msa for the design period of 20 years (i.e. from the year 2017 to 2037) Cumulative Equivalent Standard Axles for Flexible Pavement Design As explained in Section 5.2.2.6, dedicating a great percentage of the truck-trailer vehicle type to these axle configurations will definitely result in an unrealistically huge MSA and relatively thick pavement layers. In the mean time, we should not give them an unfairly small portion. That will underestimate the damage that could be imposed on the pavement by these axle configurations. Therefore, the most appealing approach is to use an average value of truck factor for each vehicle category as shown in Table 5.14. Having settled the issue of coming up with a meaningful truck factor, it is now possible to proceed to calculating Cumulative Number of Equivalent Single Axle Loads. Tables 5.18 through 5.21 show the variation of cumulative number of equivalent single axles along the years.
96 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.18: Equivalent Number of Single Axles for Bus along the years of the Base Period
Year
Bus Cum Number of Vehicles
2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037
248364.1678 505421.0814 771474.987 1046840.779 1331844.374 1626823.095 1932126.071 2248114.652 2575162.832 2913657.699 3263999.886 3626604.05 4001899.36 4390330.005 4792355.723 5208452.341 5639112.341 6084845.44 6546179.199 7023659.638
Equivalent Number of Single Axles 36592.32064 74465.37249 113663.9812 154234.5411 196225.0707 239685.2688 284666.5738 331222.2246 379407.3231 429278.9 480895.9821 534319.6622 589613.171 646841.9526 706073.7416 767378.6432 830829.2164 896500.5595 964470.3998 1034819.184
Table 5.19: Equivalent Number of Single Axles for Trucks along the years of the Base Period
Year 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028
Truck Cum Number of Vehicles 395158.5117 804147.5713 1227451.248 1665570.553 2119024.034 2588348.387 3074099.093 3576851.073 4097199.372 4635759.862 5193169.968
Equivalent Number of Single Axles 386728.4636 786992.4234 1201265.622 1630038.382 2073818.189 2533130.289 3008518.313 3500544.918 4009792.453 4536863.653 5082382.344 97
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
2029 2030 2031 2032 2033 2034 2035 2036 2037
5770089.429 6367201.071 6985211.62 7624852.538 8286880.889 8972080.232 9681261.552 10415264.22 11174956.98
AAiT, SCEE
5646994.19 6231367.45 6836193.774 7462189.02 8110094.099 8780675.857 9474727.975 10193071.92 10936557.9
Table 5.20: Equivalent Number of Single Axles for Truck-Trailers along the years of the Base Period
Year 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037
Truck and Trailer Cum Number of Equivalent Number of Vehicles Single Axles 587177.3757 6076866.424 1194905.96 12366423.18 1823905.044 18876114.41 2474919.096 25613644.83 3148718.64 32586988.83 3846101.169 39804399.87 4567892.085 47274420.28 5314945.684 55005891.42 6088146.159 63007964.04 6888408.65 71290109.21 7716680.328 79862129.45 8573941.516 88734170.41 9461206.844 97916732.79 10379526.46 107420684.9 11329987.26 117257275.2 12313714.19 127438146.3 13331871.56 137975347.8 14385664.44 148881351.4 15476340.08 160169065.2 16605189.35 171851848.9
98 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.21: Total Number of Equivalent Single Axles for all vehicles along the years of the Base Period
Year 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037
Bus 36592.32064 74465.37249 113663.9812 154234.5411 196225.0707 239685.2688 284666.5738 331222.2246 379407.3231 429278.9 480895.9821 534319.6622 589613.171 646841.9526 706073.7416 767378.6432 830829.2164 896500.5595 964470.3998 1034819.184
Equivalent Number of Single Axles Truck Truck and Trailer 386728.4636 6076866.424 786992.4234 12366423.18 1201265.622 18876114.41 1630038.382 25613644.83 2073818.189 32586988.83 2533130.289 39804399.87 3008518.313 47274420.28 3500544.918 55005891.42 4009792.453 63007964.04 4536863.653 71290109.21 5082382.344 79862129.45 5646994.19 88734170.41 6231367.45 97916732.79 6836193.774 107420684.9 7462189.02 117257275.2 8110094.099 127438146.3 8780675.857 137975347.8 9474727.975 148881351.4 10193071.92 160169065.2 10936557.9 171851848.9
Total 6500187.208 13227880.98 20191044.01 27397917.75 34857032.09 42577215.43 50567605.17 58837658.56 67397163.82 76256251.76 85425407.78 94915484.26 104737713.4 114903720.6 125425538 136315619 147586852.9 159252579.9 171326607.5 183823226
Table 5.22: Summary of Total Number of Equivalent Single Axles for all vehicles along the years of the Base Period Vehicle Traffic over the initial Mean Truck Equivalent Number of Category design period Factor Standard Single Axle Loads Cars 3690042.079 0 0 Buses 7023659.638 0.147333333 1034819.184 Trucks 11174956.98 0.978666667 10936557.9 Truck - Trailers 16605189.35 10.34928571 171851848.9* Cumulative Number of Standard Single Axle Load 183823225.9 * No correction for flexible pavements! As can be seen from Table 5.17 and Table 5.22, 175 msa and 183 msa were inspected for Rigid Pavement and Flexible Pavement respectively. This difference is attributed to the fact that Rigid Pavements are less susceptible to heavy truck loads greater than the standard axle. In addition Fatigue is of minor importance when comes to rigid pavements, especially when compared to flexible pavements. 99 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
5.3 Subgrade Soil CBR The roadway alignment of the section from Adama (Nazareth) to Awash is 125 kms. It is therefore safe to say that it requires at the very least: 4 indicator tests and 2 strength tests per km. Subgrade strength (CBR) tests of 250 are required for better pavement structure design as a least requirement. But in the mean time, we would like to clarify that these whole values were not acquired due to the following reason: The existing flexible pavement of the section was designed many years before and soil investigation reports were not available to the required extent (when ERA archived it at their Alem-Gena office). In such cases, few subgrade CBR values of the stations around Lake Beseka (Under the Re-Alignment work - 2011) and Metehara (Feasibility Study of Rigid Pavements in Ethiopia – Trial 1 km Section – 2011/12) were acquired. But more importantly, for better and all rounded outcomes of the research, representative soil subgrade CBR values reflecting common Ethiopian localities have been considered in supplementing the design. This is aimed at extracting reliable conclusions regarding the Implication of Rigid Pavement Construction in Ethiopian Road Construction as this remains one of the primary objectives of this paperwork. The following sections can be referred for more details. For the trial rigid pavement section constructed at Metehara, we have found the subgrade CBR representative for the 1 km length from ERA (Feasibility Study of Rigid Pavements in Ethiopia, 2011) and it was Black Cotton Soil of CBR equal to 15. [11]And the CBR values around Lake Beseka were found from (Core Consulting Engineers Plc. August 2011), Detail Engineering Design for the Re-alignment of Beseka Crossing (Metehara Railway Crossing – Awash Junction) Road Project. The following table can be referred for the CBR values adopted: Table 5.23: Subgrade CBR at Lake Beseka and Metehara Location
Lake Beseka [9]
Metehara [11]
Station (from relative end)
CBR (%)
Subgrade Remark
0 + 500
32
--
1 + 500 2 + 500 3 + 500 4 + 500 5 + 500 6 + 500 7 + 200 --
22 35 90 90 90 86 35 15
--Rocky Rocky Rocky Rocky -Black Cotton
100 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
As can be seen from Table 5.23, lower subgrade CBR values were also actually encountered.
5.4 Rigid Pavement Design (JRCP) According to ERA, 2002 Even though we have mentioned qualitatively in Section 3.1 and Section 5.1 that ERA Pavement Design Manual, Volume II (2002) is not a complete document to extract reliable design results, this research here by conducts the design as per the guidelines of Chapter 7 of the manual. That is, we follow the required procedures of the sections of the Chapter. This way, we may forward general comments towards the manual’s coverage of Rigid Pavement Design. Additionally, in comparison to AASHTO design guide (1993), we may contrast the pavement structure thicknesses and material constituents along with the depth of design considerations and requirements.
5.4.1 20 years Design Period We shall make use of the series of curves of ERA, Pavement Design Manual – Volume II (2002) as illustrated in Chapter 3, Figures 3.8 to 3.9. Figure 3.8 –Capping Layer and Sub Base thicknesses Figure 3.9 –Cement Concrete Slab thickness and longitudinal reinforcement Figure 3.10 –Additional Thickness if Lateral Support is not provided Referring the aforementioned three graphs, we may acquire the design values as presented in Table 5.24 and Table 5.25.
101 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.24: Capping Layer, Subbase and Slab thicknesses as well as longitudinal reinforcement (175 msa) Soil Subgrade Capping Layer Subbase Thickness CBR (%) Thickness (mm) (mm) 2 450 150 3 383.3 150 4 316.7 150 5 250 150 6 240 150 7 230 150 8 220 150 9 210 150 10 200 150 11 190 150 12 180 150 13 170 150 14 160 150 15 150 150 16 0 150 20 0 150 22 0 150 25 0 150 30 0 150 31 0 0 32 0 0 35 0 0 86 0 0 90 0 0 * Low CBR values to see further implications ** Data at locations along the alignment
As = 500 mm2/m 267 267 267 267 267 267 267 267 267 267 267 267 267 267 267 267 267 267 267 267 267 267 267 267
Slab Thickness (mm) As = 600 As = 700 2 mm /m mm2/m 251.5 240 251.5 240 251.5 240 251.5 240 251.5 240 251.5 240 251.5 240 251.5 240 251.5 240 251.5 240 251.5 240 251.5 240 251.5 240 251.5 240 251.5 240 251.5 240 251.5 240 251.5 240 251.5 240 251.5 240 251.5 240 251.5 240 251.5 240 251.5 240
Remark As = 800 2 mm /m 227.5 Low CBR* 227.5 Low CBR* 227.5 Low CBR* 227.5 Low CBR* 227.5 Low CBR* 227.5 Low CBR* 227.5 Low CBR* 227.5 Low CBR* 227.5 Low CBR* 227.5 Low CBR* 227.5 Low CBR* 227.5 Low CBR* 227.5 Low CBR* 227.5 Metehara** 227.5 High CBR* 227.5 High CBR* 227.5 Beseka 1** 227.5 High CBR* 227.5 High CBR* 227.5 High CBR* 227.5 Beseka 2** 227.5 Beseka 3** 227.5 Beseka 4 (Rocky)** 227.5 Beseka 5 (Rocky)**
102 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Figure 5.8: Capping Layer, Subbase and Slab thicknesses as well as longitudinal reinforcement 103 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
The curve in Figure 3.10 provided for additional thicknesses in cases where lateral supports are not provided can be given by the following equation. Tad = 0.07 * Tslab + 13.25 . . . . . . . . . . . . . . . . (5.11) Where: Tad is the additional thickness in mm, TSlab is the Slab thickness in mm Table 5.25: Additional thicknesses where there is no lateral Support (175 msa) As (mm2/m) T Slab (mm) T Additional (mm) T total (mm) 500 267 31.94 298.94 600 251.5 30.855 282.355 700 240 30.05 270.05 800 227.5 29.175 256.675
T Provided (mm) 300 285 270 260
And the longitudinal joint spacing for all Subgrade classes and cumulative standard axles is equal to 25 meters.
5.4.2 25, 30, 35 and 40 years Design Period The previous rigid pavement design values were obtained for 175 million standard axles expected from the year 2017 to 2037 according to ERA Pavement Design Manual – Volume II (2002). But since rigid pavements are naturally designed for periods up to 40 years, we, hereby design for 5 year increments from the year 2037 to 2057 (that is: 25, 30, 35 and 40 years design periods). But at the same time, the flexible pavement designed in the subsequent section will traverse after its base period (up to the designated 40 years) through the same stage years with: major rehabilitation (for 5 years interval), routine maintenance and periodic overlay.
104 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.26: Cumulative Number of Vehicles for the Design Periods of 25, 30, 35 and 40 years Cumulative Vehicle Volume for a Design Period * AADTi in 2017 (in Vehicle AADTi in AADTi in one direction and in 25 years (from 2017 30 years (from 35 years (from 40 years (from No Category 2009 2017 the design lane) to 2042) 2017 to 2047) 2017 to 2052) 2017 to 2057) 352 595.8167182 357.4900309 4179437.186 5293479.619 6523472.5 7881483.994 1 Cars 670 1134.082958 680.4497747 7955178.734 10075657.23 12416837 15001688.28 2 Buses 1066 1804.376766 1082.626059 12657045.57 16030821.8 19755743 23868357.78 3 Trucks 1584 2681.175232 1608.705139 18807467.34 23820658.29 29355626 35466677.97 4 Truck - Trailers Total 3672 6215.451674 3729.271004 43 599 128.82 55 220 616.94 68 051 679 82 218 208.03 * Here Traffic growth of 2 % for the period 2037 to 2057 has been assumed instead of 3.5% (for 2017 up to 2037) for the same reasons mentioned in Section 5.2.2.1 as well as the anticipated Road development 40 years from now Table 5.27: Cumulative Million Standard Axles in the Design Periods of 25, 30, 35 and 40 years
Vehicle Category
Truck Correction Factor
Factor
25 years
30 years
35 years
40 years
Cumulative
Standard
Cumulative
Standard
Cumulative
Standard
Cumulative
Standard
Vehicles
Axles
Vehicles
Axles
Vehicles
Axles
Vehicles
Axles
Cars
0
1
4179437
0
5293479
0
6523472
0
7881483
0
Buses
0.143
1
7955178
1137590
10075657
1440819
12416836
1775607
15001688
2145241
Trucks
0.977
1
12657045
12365933
16030821
15662113
19755743
19301361
23868357
23319385
0.95
18807467
184906555
23820658
234193993
29355626
288611306
35466677
348692417
Truck - Trailers 10.349 Total
198410079
251296925
309688275
374157044 105
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.28: Capping Layer, Subbase and Slab thicknesses and as well as longitudinal reinforcement (198 msa) Soil Subgrade Capping Layer Subbase Thickness CBR (%) Thickness (mm) (mm) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 - 30 > 30
450 383.3 316.7 250 240 230 220 210 200 190 180 170 160 150 0 0
150 150 150 150 150 150 150 150 150 150 150 150 150 150 150 0
As = 500 mm2/m 275 275 275 275 275 275 275 275 275 275 275 275 275 275 275 275
Slab Thickness (mm) As = 600 As = 700 2 mm /m mm2/m 260 247.5 260 247.5 260 247.5 260 247.5 260 247.5 260 247.5 260 247.5 260 247.5 260 247.5 260 247.5 260 247.5 260 247.5 260 247.5 260 247.5 260 247.5 260 247.5
As = 800 mm2/m 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233 233
Table 5.29: Additional Thicknesses where there is no lateral support (198 msa) As (mm2/m) T Slab (mm) T Additional (mm) T total (mm) 500 275 32.5 307.5 600 260 31.45 291.45 700 247.5 30.575 278.075 800 233 29.56 262.56
T Provided (mm) 310 295 280 265
106 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.30: Capping Layer, Subbase and Slab thicknesses and as well as longitudinal reinforcement (251 msa) Soil Subgrade Capping Layer Subbase Thickness CBR (%) Thickness (mm) (mm) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 - 30 > 30
450 383.3 316.7 250 240 230 220 210 200 190 180 170 160 150 0 0
150 150 150 150 150 150 150 150 150 150 150 150 150 150 150 0
As = 500 mm2/m 288 288 288 288 288 288 288 288 288 288 288 288 288 288 288 288
Slab Thickness (mm) As = 600 As = 700 2 mm /m mm2/m 270 258 270 258 270 258 270 258 270 258 270 258 270 258 270 258 270 258 270 258 270 258 270 258 270 258 270 258 270 258 270 258
As = 800 mm2/m 244 244 244 244 244 244 244 244 244 244 244 244 244 244 244 244
Table 5.31: Additional Thicknesses where there is no lateral support (251 msa) As (mm2/m) T Slab (mm) T Additional (mm) T total (mm) 500 288 33.41 321.41 600 270 32.15 302.15 700 258 31.31 289.31 800 244 30.33 274.33
T Provided (mm) 325 305 290 275
107 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.32: Capping Layer, Subbase and Slab thicknesses and as well as longitudinal reinforcement (310 msa) Soil Subgrade Capping Layer Subbase Thickness CBR (%) Thickness (mm) (mm) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 - 30 > 30
450 383.3 316.7 250 240 230 220 210 200 190 180 170 160 150 0 0
150 150 150 150 150 150 150 150 150 150 150 150 150 150 150 0
As = 500 mm2/m 300 300 300 300 300 300 300 300 300 300 300 300 300 300 300 300
Slab Thickness (mm) As = 600 As = 700 2 mm /m mm2/m 282 267 282 267 282 267 282 267 282 267 282 267 282 267 282 267 282 267 282 267 282 267 282 267 282 267 282 267 282 267 282 267
As = 800 mm2/m 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255 255
Table 5.33: Additional Thicknesses where there is no lateral support (310 msa) As (mm2/m) T Slab (mm) T Additional (mm) T total (mm) 500 300 34.25 334.25 600 282 32.99 314.99 700 267 31.94 298.94 800 255 31.1 286.1
T Provided (mm) 335 315 300 290
108 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.34: Capping Layer, Subbase and Slab thicknesses and as well as longitudinal reinforcement (374 msa) Soil Subgrade Capping Layer Subbase Thickness CBR (%) Thickness (mm) (mm) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 - 30 > 30
450 383.3 316.7 250 240 230 220 210 200 190 180 170 160 150 0 0
150 150 150 150 150 150 150 150 150 150 150 150 150 150 150 0
As = 500 mm2/m 308 308 308 308 308 308 308 308 308 308 308 308 308 308 308 308
Slab Thickness (mm) As = 600 As = 700 2 mm /m mm2/m 289 276 289 276 289 276 289 276 289 276 289 276 289 276 289 276 289 276 289 276 289 276 289 276 289 276 289 276 289 276 289 276
As = 800 mm2/m 264 264 264 264 264 264 264 264 264 264 264 264 264 264 264 264
Table 5.35: Additional Thicknesses where there is no lateral support (374 msa) As (mm2/m) T Slab (mm) T Additional (mm) T total (mm) 500 308 34.81 342.81 600 289 33.48 322.48 700 276 32.57 308.57 800 264 31.73 295.73
T Provided (mm) 345 325 310 300
109 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
5.5 Rigid Pavement Design (JRCP) as per AASHTO, 1993 In the previous section, that is Section 5.4, we have followed the ERA, Pavement Design Manual – Volume II (2002), Chapter 7 design procedures to design the pavement structure. But there is a considerable number of drawbacks that can be pointed out, especially when compared to the much detailed AASHTO Rigid Pavement Design Guide. We will compare the results briefly in Section 5.6. The following sub sections illustrate the design of rigid pavement according to AASHTO, Guide for Design of Pavement Structures – Volume I (1993).
5.5.1 Effective Modulus of Subgrade Reaction (k-value) The Effective Modulus of Subgrade Reaction (k-value) is dependent on several factors. Therefore, we shall go through several steps to arrive at a reasonable estimate.[13] 5.5.1.1 Input Variables i. Subbase Type It is very essential in estimating an effective k-value and provides a basis for evaluating cost-effectiveness as part of the design process. For our case, only one subbase type is taken. This is because the data we investigated happens to be the Soils and Material Report of Core Consulting Engineers in the Realignment of Beseka Crossing (2011) with a 7km length and only one potential gravel source. This borrow gravel material belongs to the class A- 1- b (0) granular material, with a CBR of 81%, negligible swelling and non plastic nature.[14] ii. Subbase Thickness (inch) For this study, two potential design thicknesses of the subbase are used for comparison of design outputs. They are: Small subbase thickness of 150 mm (5.906 inches) which includes no capping layer and Large subbase thickness of 400 mm (15.75 inches) which also incorporates equivalent subbase thickness of capping layer This is because: One: even according to ERA, the only subbase thickness recommended is 150 mm and it can be used to compare with the design results of Section 5.4. Second: to see if availability of large subbase thickness enhances the reduction in PCC slab thickness (i.e. decrease cost of Rigid Pavement alternative) iii. Loss of support, LS This factor is used to correct the effective k-value based on potential erosion of the subbase material. And from Table 2.7 of Part II (AASHTO, 1993), LS ranges from 1 to 3 for Unbound Granular Materials. And as can be recalled from Section 2.3.4.3 of this 110 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
research, LS of 2 to 3 is recommended for swelling Clays. Therefore, it is reasonable to assume a LS = 1.5 for non swelling subbase. iv. Depth to rigid foundation (feet) If bedrock lies within 3.28 m (10 feet) of the surface of the subgrade for any significant length along the project, its effect on the overall k-value and the design slab thickness for that segment should be considered. In our segment, continuous 3 km length stretch was investigated for their bed rock near the ground surface around Lake Beseka. 5.5.1.2 Seasonal Resilient Roadbed Modulus This shall be obtained for 12 months from January to December from field and laboratory tests. But due to unavailability of such data, the researchers have adopted the empirical equation elaborated in Section 2.2.3, Equation 2.3 which allows the Resilient Modulus to be obtained from Subgrade CBR. It is also believed that deviation from the actual value will be encountered in that: the seasonal variation is not considered and the soils and the environment in U.S.A are different from Ethiopia. But we may proceed by considering certain reductions for wet seasons. The following two equations are empirical relations employed for resilient modulus and relative damage respectively (in case of limited data): MR (psi) = 1500 X CBR . . . . . . (5.12) MR Wet = 0.75 * MR Dry (In case of data shortage) . . . . . . (5.13) U f = 1.18 * 108 * MR-2.32 . . . . . . . (5.14) To address the worst case scenario, i.e. the wet season, we shall firstly calculate the wet season resilient modulus to be 75 % of the dry season value. Then, effective modulus of subgrade reaction must be obtained from it. Then finally, the PCC slab thickness will be computed indirectly.
111 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.36: Road Bed Resilient Modulus and relative Damage for Dry and Wet Seasons Soil Subgrade CBR (%) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
Dry Season Roadbed Wet Season Roadbed MR (psi) MR (psi) Remark 3000 2250 Low CBR* 4500 3375 Low CBR* 6000 4500 Low CBR* 7500 5625 Low CBR* 9000 6750 Low CBR* 10500 7875 Low CBR* 12000 9000 Low CBR* 13500 10125 Low CBR* 15000 11250 Low CBR* 16500 12375 Low CBR* 18000 13500 Low CBR* 19500 14625 Low CBR* 21000 15750 Low CBR* 22500 16875 Metehara** 24000 18000 High CBR* 30000 22500 High CBR* 33000 24750 Beseka 1** 37500 28125 High CBR* 45000 33750 High CBR* 46500 34875 High CBR* 48000 36000 Beseka 2** 52500 39375 Beseka 3** 129000 96750 Beseka 4 (Rocky)** 135000 101250 Beseka 5 (Rocky)**
* Low CBR values to see further implications ** Data at locations along the alignment 5.5.1.3 Subbase Elastic Resilient Modulus, ESB For those types of subbase material which are insensitive to season, a constant value of subbase modulus may be assigned for each season and such scenario corresponds to our case. This implies: CBR subbase = 81% and using Equation (5.12), ESB = 121,500 psi or 121.5 ksi. For unbound materials, the ratio of the subbase to the roadbed soil resilient modulus should not exceed 4 to prevent an artificial condition. For our consideration, only those subgrades of CBR > 20 % are validated.
112 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
5.5.1.4 Composite Modulus of Subgrade Reaction, k This parameter is evaluated graphically by assuming a semi-infinite depth of the subgrade for each road bed values of ESB and MR (Wet – for worst scenario). We may use Figure 3.1 and it is read as shown in Figure 5.9.
Figure 5.9: Obtaining Composite Subgrade Modulus of Reaction In Figure 5.10, we have assumed a projected thickness of the slab of 9 inches or 228.6 mm. And knowing the fact that rigid foundation doesn’t exist within 10ft depth for much of the stretch, it is correct to neglect the provision for further adjustment. This implies Composite k-value = Effective k-value.
113 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Figure 5.10: Graphical Determination of Relative Damage, Uf, from the Corresponding Composite Subgrade Reaction
114 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Figure 5.11: Corrected k-value of LS = 1.5 (Unbound Granular Material of No Swelling Subbase)
115 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.37: Composite (Effec.) k-value, relative damage and corrected k-value for LS = 1.5 Composite (Effective) Modulus of Subgrade Reaction k (pci) 2250 207 3375 285 4500 320 5625 380 6750 450 7875 500 9000 590 10125 630 11250 760 12375 800 13500 875 14625 935 15750 1000 16875 1115 18000 1180 22500 1450 24750 1575 28125 1700 33750 1900 34875 2000 36000 2400* 39375 2900* 96750 4100* 101250 4400* * Extrapolated with compromised precision
Soil Subgrade CBR (%) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
Wet Season MR Wet (psi)
Corrected kvalue for LS = Decimal 1.5 (pci) 0.875 43.5 0.8 53 0.76 60 0.71 66 0.65 75.5 0.625 81.75 0.6 89 0.55 98 0.5 108 0.49 120 0.46 125 0.44 138 0.425 144 0.405 152 0.385 160 0.345 169 0.32 186 0.3 195.5 0.265 197.5 0.255 200 0.2475* 215* 0.235* 233* 0.2225* 250* 0.205* 268*
Relative Damage, U f % 87.5 80 76 71 65 62.5 60 55 50 49 46 44 42.5 40.5 38.5 34.5 32 30 26.5 25.5 24.75* 23.5* 22.25* 20.5*
5.5.2 Thickness Design It may be estimated for each k-value identified in the previous sections through the use of predetermined nomograph or formula (Equation (5.15)). Additionally, the following design parameters are also considered: 1. The Estimated Future Traffic, W18 in cumulative standard axles Table 5.38: The Estimated Future Traffic, W18, in the Design Period Design Period (Years) 20 25 30 35 40
W 18 (in standard axles) 175 000 000 198 000 000 251 000 000 310 000 000 374 000 000 116
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
2. Reliability, R – in percent R = 95 % can be taken for interstate rural roadway from Table 2.4 3. Total/Overall Standard Deviation, So – in decimal It is for any uncertainties present either in the estimated future traffic or pavement performance. For rigid pavements, a value of 0.35 is regularly used. 4. Design Serviceability Loss, PSI = Pi-Pt (initial minus terminal) As of Section 2.3.2.1, the initial serviceability (Pi) is 4.5 for Rigid Pavements and the terminal serviceability (Pt) is 2.5 for high traffic roadways. This gives a design serviceability loss of 2, i.e. PSI =4.5 – 2.5 = 2 5. Normal Standard Deviate, ZR It is equal to -1.645 for Reliability of 95 % (AASHTO, 1993 Part I, Chapter 4) 6. Concrete Elastic Modulus, Ec To compare to local code regarding Concrete Mechanical behavior, we may refer the nation’s code, i.e. Ethiopian Building Code of Standard – Structural Use of Concrete (EBCS – 2, 1995). Since we will use C-35 concrete grade, the tensile capacity of concrete is given by: fctk (Characteristic Tensile Strength of Concrete) = 0.3 * fck2/3 [15] fck (Characteristic Compressive Strength of Concrete) = 0.8*35 fck = 28 Mpa (Considering Site Condition) fctk = 0.3 * 28 2/3 = 2.77 Mpa and fctd (for Design)= fctk/c = 2.77/1.5 = 1.85 Mpa But for roadway pavement construction, we may have 4.5 Mpa flexural capacity. This is enhanced because of two reasons: One, due to the nature of roadway pavements (fully supported) and the aid by Admixtures. [11] Again, as of EBCS-2 (1995), Ecm = (fck + 8) 1/3=(fck + 8) 1/3 = 31.4Gpa [15] Converting to psi, Ecm (psi) = (31.4 * 10 9 N/m2) / 6894.8 = 4.5 * 10 6 psi According to AASHTO, 1993 – Part II, Chapter 3, Ec =5 * 10 6 psi is recommended for Highway Construction. So we adopt this value. 7. Concrete Modulus of Rupture, Sc’ It is approximately equal to the flexural strength of Concrete: Sc’ = 4.8 Mpa (4 800 000 pa / 6894.8) = 687.21 psi (A very close value to that recommended by AASHTO; fc’ or Sc’ = 650 psi) (AASHTO, 1993 Part II, Chapter 3) 8. Load Transfer Coefficient, J According to Section 2.4.2 of AASHTO, 1993 Part II, J = 3.2 for JRCP with load transfer devices is recommended. 9. Drainage Coefficient, Cd A value of Cd= 1.15 is adopted from Table 2.4 of AASHTO, 1993 Part II 10. Corrected k-value, k For different roadbed conditions, the values from the previous section can be adopted in pci. However, k-value and W 18 are the only variables for our case. 117 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
∆𝐏𝐒𝐈 ] 𝟒. 𝟓 − 𝟏. 𝟓 𝐥𝐨𝐠 𝟏𝟎 (𝐖𝟏𝟖 ) = 𝐙𝐑 𝐱 𝐒𝐨 + 𝟕. 𝟑𝟓 𝐱 𝐥𝐨𝐠 𝟏𝟎 (𝐃 + 𝟏) − 𝟎. 𝟎𝟔 + 𝟏. 𝟔𝟐𝟒 𝐱 𝟏𝟎𝟕 𝟏+ (𝐃 + 𝟏)𝟖.𝟒𝟔 𝐥𝐨𝐠 𝟏𝟎 [
𝐒𝐜′ 𝐱 𝐂𝐝 𝐱 (𝐃𝟎.𝟕𝟓 − 𝟏. 𝟏𝟑𝟐)
+ (𝟒. 𝟐𝟐 − 𝟎. 𝟑𝟐 𝐱 𝐩𝐭 ) 𝐱 𝐥𝐨𝐠 𝟏𝟎
𝟐𝟏𝟓. 𝟔𝟑𝐱 𝐉 𝐱 [𝐃𝟎.𝟕𝟓 − [ Leaving W 18, D and k to be variables in that W rest and find that:
18 and
. . (𝟓. 𝟏𝟓)
𝟏𝟖. 𝟒𝟐 ] 𝐄𝐜 𝟎.𝟐𝟓 ( ) ] 𝐤
k yield D, we may substitute the
𝟐 ] 𝟒. 𝟓 − 𝟏. 𝟓 𝐥𝐨𝐠 𝟏𝟎 (𝐖𝟏𝟖 ) = −𝟏. 𝟔𝟒𝟓 𝐱 𝟎. 𝟑𝟓 + 𝟕. 𝟑𝟓 𝐱 𝐥𝐨𝐠 𝟏𝟎 (𝐃 + 𝟏) − 𝟎. 𝟎𝟔 + 𝟏. 𝟔𝟐𝟒 𝐱 𝟏𝟎𝟕 𝟏+ (𝐃 + 𝟏)𝟖.𝟒𝟔 + (𝟒. 𝟐𝟐 𝐥𝐨𝐠 𝟏𝟎 [
𝟔𝟖𝟕. 𝟐𝟏 𝐱 𝟏. 𝟏𝟓 𝐱 (𝐃𝟎.𝟕𝟓 − 𝟏. 𝟏𝟑𝟐)
− 𝟎. 𝟑𝟐 𝐱 𝟐. 𝟓) 𝐱 𝐥𝐨𝐠 𝟏𝟎
𝟐𝟏𝟓. 𝟔𝟑𝐱𝟑. 𝟐 𝐱 [𝐃𝟎.𝟕𝟓 − [
𝟏𝟖. 𝟒𝟐 ] 𝟓𝟎𝟎𝟎𝟎𝟎𝟎 𝟎.𝟐𝟓 ( ) ] 𝐤
−𝟎. 𝟏𝟕𝟔𝟏 𝟏. 𝟔𝟐𝟒 𝐱 𝟏𝟎𝟕 𝟏+ (𝐃 + 𝟏)𝟖.𝟒𝟔 𝟏. 𝟏𝟒𝟓𝟑𝟐𝟑 𝐱 (𝐃𝟎.𝟕𝟓 − 𝟏. 𝟏𝟑𝟐) + 𝟑. 𝟒𝟐 𝐱 𝐥𝐨𝐠 𝟏𝟎 [ ] [𝐃𝟎.𝟕𝟓 − 𝟎. 𝟑𝟖𝟗𝟓𝟒(𝐤)𝟎.𝟐𝟓 ]
𝐥𝐨𝐠 𝟏𝟎 (𝐖𝟏𝟖 ) = −𝟎. 𝟔𝟑𝟓𝟕𝟓 + 𝟕. 𝟑𝟓 𝐱 𝐥𝐨𝐠 𝟏𝟎 (𝐃 + 𝟏) +
In Table 5.39, it should be noted that: since we have not used capping layer for any subgrade CBR and set a constant small subbase thickness of 150 mm (5.91 inches), very large slab thicknesses were encountered. To be economical, we will retry by increasing the subbase thickness which contains: the granular subbase material plus equivalent capping layer thickness. The following simple formula can explain it easily: T total of subbase = T subbase granular (gravel source) + T equivalent subbase to capping layer. . . . (5.16)
118 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.39: Slab Thicknesses for different Design Periods but for Constant Small Subbase Thickness of 150mm and no Capping Layer (All the mm values shall be rounded up to the next higher 5 or 10 mm (depending on the expertise) on actual purposes) 175 msa Soil Subgrade CBR (%) k (pci) D (inches) D (mm) 2 43.5 15.1634 385.15036 3 53 15.1063 383.70002 4 60 15.0684 382.73736 5 66 15.0384 381.97536 6 75.5 14.9944 380.85776 7 81.75 14.96765 380.17831 8 89 14.9384 379.43536 9 98 14.90415 378.56541 10 108 14.8684 377.65736 11 120 14.8286 376.64644 12 125 14.8129 376.24766 13 138 14.7737 375.25198 14 144 14.7564 374.81256 15 152 14.7343 374.25122 16 160 14.712775 373.704485 20 169 14.6894 373.11076 22 186 14.6477 372.05158 25 195.5 14.6257 371.49278 30 197.5 14.6209 371.37086 31 200 14.6154 371.23116 32 215 14.5819 370.38026 35 233 14.54405 369.41887 86 250 14.5104 368.56416 90 268 14.476 367.6904
198 msa D (inches) 15.4349 15.3778 15.3399 15.3099 15.2659 15.23915 15.2099 15.17565 15.1399 15.1001 15.0844 15.0452 15.0279 15.0058 14.98428 14.9609 14.9192 14.8972 14.8924 14.8869 14.8534 14.81555 14.7819 14.7475
251 msa
D (mm) D (inches) 392.04646 15.9697 390.59612 15.9126 389.63346 15.8747 388.87146 15.8447 387.75386 15.8007 387.07441 15.77395 386.33146 15.7447 385.46151 15.71045 384.55346 15.6747 383.54254 15.6349 383.14376 15.6192 382.14808 15.58 381.70866 15.5627 381.14732 15.5406 380.60059 15.51908 380.00686 15.4957 378.94768 15.454 378.38888 15.432 378.26696 15.4272 378.12726 15.4217 377.27636 15.3882 376.31497 15.35035 375.46026 15.3167 374.5865 15.2823
D (mm) 405.6304 404.18 403.2174 402.4554 401.3378 400.6583 399.9154 399.0454 398.1374 397.1265 396.7277 395.732 395.2926 394.7312 394.1845 393.5908 392.5316 391.9728 391.8509 391.7112 390.8603 389.8989 389.0442 388.1704
310 msa D (inches) 16.4605 16.4034 16.3655 16.3355 16.2915 16.26475 16.2355 16.20125 16.1655 16.1257 16.11 16.0708 16.0535 16.0314 16.00988 15.9865 15.9448 15.9228 15.918 15.9125 15.879 15.84115 15.8075 15.7731
D (mm) 418.0967 416.6464 415.6837 414.9217 413.8041 413.1247 412.3817 411.5118 410.6037 409.5928 409.194 408.1983 407.7589 407.1976 406.6508 406.0571 404.9979 404.4391 404.3172 404.1775 403.3266 402.3652 401.5105 400.6367
374 msa D (inches) 16.9085 16.8514 16.8135 16.7835 16.7395 16.71275 16.6835 16.64925 16.6135 16.5737 16.558 16.5188 16.5015 16.4794 16.457875 16.4345 16.3928 16.3708 16.366 16.3605 16.327 16.28915 16.2555 16.2211
D (mm) 429.4759 428.02556 427.0629 426.3009 425.1833 424.50385 423.7609 422.89095 421.9829 420.97198 420.5732 419.57752 419.1381 418.57676 418.030025 417.4363 416.37712 415.81832 415.6964 415.5567 414.7058 413.74441 412.8897 412.01594 119
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
5.5.3 PCC Slab Thickness Design with Revised Subbase Thickness of 400 mm – 15.75 inches – Which also Includes Capping Layer Composite Modulus of Subgrade Reaction, k This parameter is evaluated graphically by assuming a semi-infinite depth of the subgrade for each road bed values of ESB and MR (Wet – for worst scenario). We may use Figure 5.12.
Figure 5.12: Determination of Composite Subgrade Modulus of Reaction
120 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Figure 5.13: Corrected k-value for LS = 1.5 (Unbound Granular Material of Non Swelling Subbase)
121 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.40: Composite (Effec.) k-value, relative damage and corrected k-value for LS = 1.5 Composite (Effective) Modulus of Subgrade Reaction k (pci) 2 2250 395 3 3375 480 4 4500 600 5 5625 800 6 6750 910 7 7875 1000 8 9000 1065 9 10125 1100 10 11250 1345 11 12375 1400 12 13500 1460 13 14625 1500 14 15750 1580 15 16875 1650 16 18000 1925 20 22500 2000 22 24750 2175 25 28125 2475 30 33750 2600 31 34875 2715 32 36000 3750* 35 39375 4200* 86 96750 5500* 90 101250 5950* * Extrapolated with compromised precision Soil Subgrade CBR (%)
Wet Season MR Wet (psi)
Corrected k-value for LS = 1.5 (pci) 78.368 95.623 119.983 160.583 182.913 201.183 214.378 221.483 271.218 282.383 294.563 302.683 318.923 333.133 388.958 404.183 439.708 500.608 525.983 549.328 759.433* 850.783* 1114.68* 1206.03*
Thickness Design −𝟎. 𝟏𝟕𝟔𝟏 𝟏. 𝟔𝟐𝟒 𝐱 𝟏𝟎𝟕 𝟏+ (𝐃 + 𝟏)𝟖.𝟒𝟔 𝟏. 𝟏𝟒𝟓𝟑𝟐𝟑 𝐱 (𝐃𝟎.𝟕𝟓 − 𝟏. 𝟏𝟑𝟐) + 𝟑. 𝟒𝟐 𝐱 𝐥𝐨𝐠 𝟏𝟎 [ ] [𝐃𝟎.𝟕𝟓 − 𝟎. 𝟑𝟖𝟗𝟓𝟒(𝐤)𝟎.𝟐𝟓 ]
𝐥𝐨𝐠 𝟏𝟎 (𝐖𝟏𝟖 ) = −𝟎. 𝟔𝟑𝟓𝟕𝟓 + 𝟕. 𝟑𝟓 𝐱 𝐥𝐨𝐠 𝟏𝟎 (𝐃 + 𝟏) +
122 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.41: Slab Thicknesses for different Design Periods for Constant Subbase Thickness of 400mm with Capping Layer (All the mm values shall be rounded up to the next higher 5 or 10 mm (depending on the expertise) on actual purposes) Soil Subgrade CBR (%) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
175 msa k (pci) D (inches) 78.37 14.9834 95.623 14.9147 119.983 14.8308 160.583 14.71365 182.913 14.65755 201.183 14.615 214.378 14.5857 221.483 14.5705 271.218 14.4717 282.383 14.4513 294.563 14.4295 302.683 14.4153 318.923 14.3877 333.133 14.3641 388.958 14.2775 404.183 14.2554 439.708 14.2054 500.608 14.1255 525.983 14.0936 549.328 14.0655 759.433 13.8385 850.783 13.7515 1114.68 13.5265 1206.03 13.4555
D (mm) 380.57836 378.83338 376.70232 373.72671 372.30177 371.221 370.47678 370.0907 367.58118 367.06302 366.5093 366.14862 365.44758 364.84814 362.6485 362.08716 360.81716 358.7877 357.97744 357.2637 351.4979 349.2881 343.5731 341.7697
198 msa D (inches) 15.25482 15.18612 15.10222 14.98507 14.92897 14.88642 14.85712 14.84192 14.74312 14.72272 14.70092 14.68672 14.65912 14.63552 14.54892 14.52682 14.47682 14.39692 14.36502 14.33692 14.10992 14.02292 13.79792 13.72692
251 msa
D (mm) D (inches) 387.47243 15.78905 385.72745 15.72035 383.59639 15.63645 380.62078 15.5193 379.19584 15.4632 378.11507 15.42065 377.37085 15.39135 376.98477 15.37615 374.47525 15.27735 373.95709 15.25695 373.40337 15.23515 373.04269 15.22095 372.34165 15.19335 371.74221 15.16975 369.54257 15.08315 368.98123 15.06105 367.71123 15.01105 365.68177 14.93115 364.87151 14.89925 364.15777 14.87115 358.39197 14.64415 356.18217 14.55715 350.46717 14.33215 348.66377 14.26115
D (mm) 401.0419 399.2969 397.1658 394.1902 392.7653 391.6845 390.9403 390.5542 388.0447 387.5265 386.9728 386.6121 385.9111 385.3117 383.112 382.5507 381.2807 379.2512 378.441 377.7272 371.9614 369.7516 364.0366 362.2332
310 msa D (inches) 16.2793 16.2106 16.1267 16.00955 15.95345 15.9109 15.8816 15.8664 15.7676 15.7472 15.7254 15.7112 15.6836 15.66 15.5734 15.5513 15.5013 15.4214 15.3895 15.3614 15.1344 15.0474 14.8224 14.7514
D (mm) 413.4942 411.7492 409.6182 406.6426 405.2176 404.1369 403.3926 403.0066 400.497 399.9789 399.4252 399.0645 398.3634 397.764 395.5644 395.003 393.733 391.7036 390.8933 390.1796 384.4138 382.204 376.489 374.6856
374 msa D (inches) 16.72706 16.65836 16.57446 16.45731 16.40121 16.35866 16.32936 16.31416 16.21536 16.19496 16.17316 16.15896 16.13136 16.10776 16.02116 15.99906 15.94906 15.86916 15.83726 15.80916 15.58216 15.49516 15.27016 15.19916
D (mm) 424.867 423.122 420.991 418.015 416.590 415.509 414.765 414.379 411.870 411.351 410.798 410.437 409.736 409.137 406.937 406.376 405.106 403.076 402.266 401.552 395.786 393.577 387.862 386.058 123
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
5.5.4Joint Design Part II, Section 3.3 of AASHTO Guide (1993) can be referred for further design detail. 5.5.4.1 Joint Types Generally, there are three different types of pavement joints, each with a specific purpose: Contraction joints: relieve the tensile stress due to climatic change or friction Expansion joints: when there is rise in temperature and change in subgrade reaction, they prevent the development of excessive compressive stress (leading to pavement buckling) Construction joints: which are used to facilitate construction by allowing enough clearance for machines to pave the road section 5.5.4.2 Joint Geometry 1. Spacing: of transverse and longitudinal contraction joints depends on local conditions of materials and environment, whereas expansion joints are majorly dependent on layout and construction capabilities. Other factors are temperature changes, subbase frictional resistance, slab thickness and tensile/compressive strength of concrete. According to AASHTO (1993), the spacing determination is left for an Agency or experienced professional in the area. So, for better comparison with the design using ERA (2002), let us take 25 m (984.25 inches or 82.021 feet) for longitudinal direction and 4m (157.48 inches or 13.12 feet) for the transverse direction. 2. Layout: Skewed layouts and randomization improves riding quality. 3. Dimensions: Normally joint dimensions are set by considering the desired location of crack beginning. Transverse contraction joint depths are usually ¼ of the slab thickness whereas the depths of the longitudinal ones are commonly 1/3 of the slab thickness. 4. Sealant Dimensions: of contraction, expansion and construction joints [13]
5.5.5 Rigid Pavement Reinforcement Design 5.5.5.1 Slab Reinforcement Various environmental changes, namely, temperature spikes, moisture variations and frictional resistance from the bed material necessitate distributed steel reinforcements to halt the propagation of cracks. For jointed reinforced concrete pavements, both the transverse and longitudinal reinforcement areas are determined through the use of a simple nomograph (Figure 5.14). [13] The following parameters need to be known: Slab length, L: refers to the joint spacing or distance discussed in previous sections (82.021 and 13.12 feet) Steel working stress, fs: is to be taken as 75 percent of the yield strength. 124 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
According to EBCS – 2, 1995, among the commercially available steel grade types, S-300, S-400 and S-460; we will take S-400 for steel reinforcement. [15] Therefore, S – 400 Steel Yield Stress (fyd) = fyk / s fyd = 400 / 1.15 = 347.83 Mpa and since fs = 0.75 * fyd fs = 0.75 * 347.83 = 260.83 Mpa fs = (260830000 pa) / 6894.8 = 37836 psi or 37.836 ksi Friction factor, F: this is the frictional resistance between the bottom of the slab and the top of the underlying soil or aggregate structure to be taken as F = 1.5 for Crushed stone (See Table 5.42) As % = (82.021 ft * 1.5) / (2 * 37836 psi) = 0.1661 % for Longitudinal Bars& As % = (13.12 ft * 1.5) / (2 * 37836 psi) = 0.02675 % for Transverse Bars Table 5.42: Recommended Values for Subbase and Subgrade (Source: AASHTO, 1993) Nature of material beneath slab Surface treatment Lime stabilization Asphalt stabilization Cement stabilization River gravel Crushed stone Sandstone Natural subgrade
Friction Factor (F) 2.2 1.8 1.8 1.8 1.5 1.5 1.2 0.9
Figure 5.14: Reinforcement Design Chart for Jointed Reinforced Concrete Pavements (Source: AASHTO Guide, 1993) 125 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Tables 5.43: Reinforcement Computation of The PCC Slabs for 400 mm Subbase Thickness Longitudinal (Short) and Transverse (Long) Directions – 175 msa Soil Subgrade CBR (%) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
k (pci) 78.37 95.623 119.983 160.583 182.913 201.183 214.378 221.483 271.218 282.383 294.563 302.683 318.923 333.133 388.958 404.183 439.708 500.608 525.983 549.328 759.433 850.783 1114.68 1206.03
D (inches) D (m) 15.1634 0.38515036 15.1063 0.38370002 15.0684 0.38273736 15.0384 0.38197536 14.9944 0.38085776 14.96765 0.38017831 14.9384 0.37943536 14.90415 0.37856541 14.8684 0.37765736 14.8286 0.37664644 14.8129 0.37624766 14.7737 0.37525198 14.7564 0.37481256 14.7343 0.37425122 14.712775 0.37370449 14.6894 0.37311076 14.6477 0.37205158 14.6257 0.37149278 14.6209 0.37137086 14.6154 0.37123116 14.5819 0.37038026 14.54405 0.36941887 14.5104 0.36856416 14.476 0.3676904
Longitudinal (mm2/m & all 6 12) 639.7239637 637.3149896 635.7160383 634.4503776 632.5940753 631.4655279 630.2315088 628.7865462 627.2783006 625.5991907 624.9368283 623.2830317 622.5531674 621.6207974 620.7126859 619.7265253 617.9672569 617.0391058 616.8366001 616.6045623 615.1912412 613.5943993 612.17475 610.7234591
Transverse (mm2/m & all 2 12) 103.031573 102.643592 102.386071 102.182229 101.883259 101.7015 101.502753 101.270033 101.02712 100.756689 100.650012 100.383657 100.266108 100.115944 99.9696868 99.8108594 99.5275182 99.3780336 99.3454188 99.3080476 99.0804234 98.8232419 98.5945984 98.3608589
Tables 5.44: Reinforcement Computation of The PCC Slabs for 400 mm Subbase Thickness Longitudinal (Short) and Transverse (Long) Directions – 198 msa Soil Subgrade CBR (%) 2 3 4 5 6 7 8 9 10 11
k (pci) 78.37 95.623 119.983 160.583 182.913 201.183 214.378 221.483 271.218 282.383
Longitudinal (mm2/m Transverse (mm2/m D (inches) D (m) & all 6 12) & all 2 12) 15.4349 0.39204646 651.1781928 104.876349 15.3778 0.39059612 648.7692186 104.488368 15.3399 0.38963346 647.1702673 104.230847 15.3099 0.38887146 645.9046067 104.027004 15.2659 0.38775386 644.0483044 103.728035 15.23915 0.38707441 642.9197569 103.546275 15.2099 0.38633146 641.6857378 103.347529 15.17565 0.38546151 640.2407752 103.114809 15.1399 0.38455346 638.7325296 102.871896 15.1001 0.38354254 637.0534197 102.601465 126
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
12 13 14 15 16 20 22 25 30 31 32 35 86 90
294.563 302.683 318.923 333.133 388.958 404.183 439.708 500.608 525.983 549.328 759.433 850.783 1114.68 1206.03
15.0844 0.38314376 15.0452 0.38214808 15.0279 0.38170866 15.0058 0.38114732 14.984275 0.38060059 14.9609 0.38000686 14.9192 0.37894768 14.8972 0.37838888 14.8924 0.37826696 14.8869 0.37812726 14.8534 0.37727636 14.81555 0.37631497 14.7819 0.37546026 14.7475 0.3745865
AAiT, SCEE
636.3910573 634.7372607 634.0073964 633.0750264 632.1669149 631.1807543 629.4214859 628.4933348 628.2908291 628.0587913 626.6454702 625.0486284 623.628979 622.1776881
102.494787 102.228433 102.110884 101.96072 101.814462 101.655635 101.372294 101.222809 101.190194 101.152823 100.925199 100.668018 100.439374 100.205635
Tables 5.45: Reinforcement Computation of The PCC Slabs for 400 mm Subbase Thickness Longitudinal (Short) and Transverse (Long) Directions – 251 msa Soil Subgrade CBR (%) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
k (pci) 78.37 95.623 119.983 160.583 182.913 201.183 214.378 221.483 271.218 282.383 294.563 302.683 318.923 333.133 388.958 404.183 439.708 500.608 525.983 549.328 759.433 850.783 1114.68 1206.03
D (inches) D (m) 15.9697 0.40563038 15.9126 0.40418004 15.8747 0.40321738 15.8447 0.40245538 15.8007 0.40133778 15.77395 0.40065833 15.7447 0.39991538 15.71045 0.39904543 15.6747 0.39813738 15.6349 0.39712646 15.6192 0.39672768 15.58 0.395732 15.5627 0.39529258 15.5406 0.39473124 15.519075 0.39418451 15.4957 0.39359078 15.454 0.3925316 15.432 0.3919728 15.4272 0.39185088 15.4217 0.39171118 15.3882 0.39086028 15.35035 0.38989889 15.3167 0.38904418 15.2823 0.38817042
Longitudinal (mm2/m Transverse (mm2/m & all 6 12) & all 2 12) 673.7407035 108.510183 671.3317294 108.122203 669.7327781 107.864681 668.4671174 107.660839 666.6108151 107.36187 665.4822677 107.18011 664.2482485 106.981363 662.803286 106.748643 661.2950403 106.505731 659.6159305 106.235299 658.9535681 106.128622 657.2997715 105.862267 656.5699072 105.744718 655.6375372 105.594554 654.7294256 105.448297 653.743265 105.28947 651.9839967 105.006128 651.0558456 104.856644 650.8533399 104.824029 650.6213021 104.786658 649.207981 104.559034 647.6111391 104.301852 646.1914897 104.073209 644.7401988 103.839469 127
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Tables 5.46: Reinforcement Computation of The PCC Slabs for 400 mm Subbase Thickness Longitudinal (Short) and Transverse (Long) Directions – 310 msa Soil Subgrade CBR (%) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
k (pci) 78.37 95.623 119.983 160.583 182.913 201.183 214.378 221.483 271.218 282.383 294.563 302.683 318.923 333.133 388.958 404.183 439.708 500.608 525.983 549.328 759.433 850.783 1114.68 1206.03
Longitudinal (mm2/m Transverse (mm2/m D (inches) D (m) & all 5 14) & all 2 12) 16.4605 0.4180967 694.446912 111.845048 16.4034 0.41664636 692.0379379 111.457068 16.3655 0.4156837 690.4389866 111.199547 16.3355 0.4149217 689.1733259 110.995704 16.2915 0.4138041 687.3170236 110.696735 16.26475 0.41312465 686.1884762 110.514975 16.2355 0.4123817 684.954457 110.316229 16.20125 0.41151175 683.5094944 110.083508 16.1655 0.4106037 682.0012488 109.840596 16.1257 0.40959278 680.322139 109.570165 16.11 0.409194 679.6597766 109.463487 16.0708 0.40819832 678.00598 109.197133 16.0535 0.4077589 677.2761157 109.079583 16.0314 0.40719756 676.3437456 108.929419 16.009875 0.40665083 675.4356341 108.783162 15.9865 0.4060571 674.4494735 108.624335 15.9448 0.40499792 672.6902052 108.340994 15.9228 0.40443912 671.762054 108.191509 15.918 0.4043172 671.5595483 108.158894 15.9125 0.4041775 671.3275105 108.121523 15.879 0.4033266 669.9141895 107.893899 15.84115 0.40236521 668.3173476 107.636717 15.8075 0.4015105 666.8976982 107.408074 15.7731 0.40063674 665.4464073 107.174334
Tables 5.47: Reinforcement Computation of The PCC Slabs for 400 mm Subbase Thickness Longitudinal (Short) and Transverse (Long) Directions – 374 msa Soil Subgrade CBR (%) 2 3 4 5 6 7 8 9 10
k (pci) 78.37 95.623 119.983 160.583 182.913 201.183 214.378 221.483 271.218
Longitudinal (mm2/m Transverse (mm2/m D (inches) D (m) & all 5 14) & all 2 12) 16.9085 0.4294759 713.3474446 114.889098 16.8514 0.42802556 710.9384704 114.501118 16.8135 0.4270629 709.3395191 114.243596 16.7835 0.4263009 708.0738585 114.039754 16.7395 0.4251833 706.2175562 113.740785 16.71275 0.42450385 705.0890087 113.559025 16.6835 0.4237609 703.8549896 113.360278 16.64925 0.42289095 702.410027 113.127558 16.6135 0.4219829 700.9017814 112.884646 128
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
282.383 294.563 302.683 318.923 333.133 388.958 404.183 439.708 500.608 525.983 549.328 759.433 850.783 1114.68 1206.03
16.5737 0.42097198 16.558 0.4205732 16.5188 0.41957752 16.5015 0.4191381 16.4794 0.41857676 16.457875 0.41803003 16.4345 0.4174363 16.3928 0.41637712 16.3708 0.41581832 16.366 0.4156964 16.3605 0.4155567 16.327 0.4147058 16.28915 0.41374441 16.2555 0.4128897 16.2211 0.41201594
AAiT, SCEE
699.2226716 698.5603092 696.9065125 696.1766482 695.2442782 694.3361667 693.3500061 691.5907378 690.6625866 690.4600809 690.2280431 688.814722 687.2178802 685.7982308 684.3469399
112.614214 112.507537 112.241182 112.123633 111.973469 111.827212 111.668385 111.385043 111.235559 111.202944 111.165573 110.937949 110.680767 110.452124 110.218384
Tables 5.48: Reinforcement Computation of The PCC Slabs for 150 mm Subbase Thickness Longitudinal (Short) and Transverse (Long) Directions – 175 msa Soil Subgrade CBR (%) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
k (pci) 43.5 53 60 66 75.5 81.75 89 98 108 120 125 138 144 152 160 169 186 195.5 197.5 200 215 233 250 268
D (inches) 15.1634 15.1063 15.0684 15.0384 14.9944 14.96765 14.9384 14.90415 14.8684 14.8286 14.8129 14.7737 14.7564 14.7343 14.712775 14.6894 14.6477 14.6257 14.6209 14.6154 14.5819 14.54405 14.5104 14.476
Longitudinal (mm2/m Transverse (mm2/m D (m) & all 6 12) & all 2 12) 0.38515036 639.7239637 103.031573 0.38370002 637.3149896 102.643592 0.38273736 635.7160383 102.386071 0.38197536 634.4503776 102.182229 0.38085776 632.5940753 101.883259 0.38017831 631.4655279 101.7015 0.37943536 630.2315088 101.502753 0.37856541 628.7865462 101.270033 0.37765736 627.2783006 101.02712 0.37664644 625.5991907 100.756689 0.37624766 624.9368283 100.650012 0.37525198 623.2830317 100.383657 0.37481256 622.5531674 100.266108 0.37425122 621.6207974 100.115944 0.37370449 620.7126859 99.9696868 0.37311076 619.7265253 99.8108594 0.37205158 617.9672569 99.5275182 0.37149278 617.0391058 99.3780336 0.37137086 616.8366001 99.3454188 0.37123116 616.6045623 99.3080476 0.37038026 615.1912412 99.0804234 0.36941887 613.5943993 98.8232419 0.36856416 612.17475 98.5945984 0.3676904 610.7234591 98.3608589 129
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Tables 5.49: Reinforcement Computation of The PCC Slabs for 150 mm Subbase Thickness Longitudinal (Short) and Transverse (Long) Directions – 198 msa Soil Subgrade CBR (%) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
Longitudinal (mm2/m Transverse (mm2/m k (pci) D (inches) D (m) & all 6 12) & all 2 12) 43.5 15.4349 0.39204646 651.1781928 104.876349 53 15.3778 0.39059612 648.7692186 104.488368 60 15.3399 0.38963346 647.1702673 104.230847 66 15.3099 0.38887146 645.9046067 104.027004 75.5 15.2659 0.38775386 644.0483044 103.728035 81.75 15.23915 0.38707441 642.9197569 103.546275 89 15.2099 0.38633146 641.6857378 103.347529 98 15.17565 0.38546151 640.2407752 103.114809 108 15.1399 0.38455346 638.7325296 102.871896 120 15.1001 0.38354254 637.0534197 102.601465 125 15.0844 0.38314376 636.3910573 102.494787 138 15.0452 0.38214808 634.7372607 102.228433 144 15.0279 0.38170866 634.0073964 102.110884 152 15.0058 0.38114732 633.0750264 101.96072 160 14.98428 0.38060071 632.1671258 101.814496 169 14.9609 0.38000686 631.1807543 101.655635 186 14.9192 0.37894768 629.4214859 101.372294 195.5 14.8972 0.37838888 628.4933348 101.222809 197.5 14.8924 0.37826696 628.2908291 101.190194 200 14.8869 0.37812726 628.0587913 101.152823 215 14.8534 0.37727636 626.6454702 100.925199 233 14.81555 0.37631497 625.0486284 100.668018 250 14.7819 0.37546026 623.628979 100.439374 268 14.7475 0.3745865 622.1776881 100.205635
Tables 5.50: Reinforcement Computation of The PCC Slabs for 150 mm Subbase Thickness Longitudinal (Short) and Transverse (Long) Directions – 251 msa Soil Subgrade CBR (%) 2 3 4 5 6 7 8
k (pci) D (inches) 43.5 15.9697 53 15.9126 60 15.8747 66 15.8447 75.5 15.8007 81.75 15.77395 89 15.7447
D (m) 0.40563038 0.40418004 0.40321738 0.40245538 0.40133778 0.40065833 0.39991538
Longitudinal (mm2/m Transverse (mm2/m & all 6 12) & all 2 12) 673.7407035 108.510183 671.3317294 108.122203 669.7327781 107.864681 668.4671174 107.660839 666.6108151 107.36187 665.4822677 107.18011 664.2482485 106.981363 130
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
9 10 11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
98 108 120 125 138 144 152 160 169 186 195.5 197.5 200 215 233 250 268
15.71045 15.6747 15.6349 15.6192 15.58 15.5627 15.5406 15.51908 15.4957 15.454 15.432 15.4272 15.4217 15.3882 15.35035 15.3167 15.2823
0.39904543 0.39813738 0.39712646 0.39672768 0.395732 0.39529258 0.39473124 0.39418463 0.39359078 0.3925316 0.3919728 0.39185088 0.39171118 0.39086028 0.38989889 0.38904418 0.38817042
AAiT, SCEE
662.803286 661.2950403 659.6159305 658.9535681 657.2997715 656.5699072 655.6375372 654.7296366 653.743265 651.9839967 651.0558456 650.8533399 650.6213021 649.207981 647.6111391 646.1914897 644.7401988
106.748643 106.505731 106.235299 106.128622 105.862267 105.744718 105.594554 105.448331 105.28947 105.006128 104.856644 104.824029 104.786658 104.559034 104.301852 104.073209 103.839469
Tables 5.51: Reinforcement Computation of The PCC Slabs for 150 mm Subbase Thickness Longitudinal (Short) and Transverse (Long) Directions – 310 msa Soil Subgrade CBR (%) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 20 22 25 30 31 32 35
k (pci) 43.5 53 60 66 75.5 81.75 89 98 108 120 125 138 144 152 160 169 186 195.5 197.5 200 215 233
D (inches) 16.4605 16.4034 16.3655 16.3355 16.2915 16.26475 16.2355 16.20125 16.1655 16.1257 16.11 16.0708 16.0535 16.0314 16.00988 15.9865 15.9448 15.9228 15.918 15.9125 15.879 15.84115
D (m) 0.4180967 0.41664636 0.4156837 0.4149217 0.4138041 0.41312465 0.4123817 0.41151175 0.4106037 0.40959278 0.409194 0.40819832 0.4077589 0.40719756 0.40665095 0.4060571 0.40499792 0.40443912 0.4043172 0.4041775 0.4033266 0.40236521
Longitudinal (mm2/m Transverse (mm2/m & all 5 14) & all 2 12) 694.446912 111.845048 692.0379379 111.457068 690.4389866 111.199547 689.1733259 110.995704 687.3170236 110.696735 686.1884762 110.514975 684.954457 110.316229 683.5094944 110.083508 682.0012488 109.840596 680.322139 109.570165 679.6597766 109.463487 678.00598 109.197133 677.2761157 109.079583 676.3437456 108.929419 675.435845 108.783196 674.4494735 108.624335 672.6902052 108.340994 671.762054 108.191509 671.5595483 108.158894 671.3275105 108.121523 669.9141895 107.893899 668.3173476 107.636717 131
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
86 90
250 268
15.8075 0.4015105 15.7731 0.40063674
AAiT, SCEE
666.8976982 665.4464073
107.408074 107.174334
Tables 5.52: Reinforcement Computation of The PCC Slabs for 150 mm Subbase Thickness Longitudinal (Short) and Transverse (Long) Directions – 374 msa Soil Subgrade CBR (%) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
k (pci) 43.5 53 60 66 75.5 81.75 89 98 108 120 125 138 144 152 160 169 186 195.5 197.5 200 215 233 250 268
D (inches) D (m) 16.9085 0.4294759 16.8514 0.42802556 16.8135 0.4270629 16.7835 0.4263009 16.7395 0.4251833 16.71275 0.42450385 16.6835 0.4237609 16.64925 0.42289095 16.6135 0.4219829 16.5737 0.42097198 16.558 0.4205732 16.5188 0.41957752 16.5015 0.4191381 16.4794 0.41857676 16.457875 0.41803003 16.4345 0.4174363 16.3928 0.41637712 16.3708 0.41581832 16.366 0.4156964 16.3605 0.4155567 16.327 0.4147058 16.28915 0.41374441 16.2555 0.4128897 16.2211 0.41201594
Longitudinal (mm2/m Transverse (mm2/m & all 5 14) & all 2 12) 713.3474446 114.889098 710.9384704 114.501118 709.3395191 114.243596 708.0738585 114.039754 706.2175562 113.740785 705.0890087 113.559025 703.8549896 113.360278 702.410027 113.127558 700.9017814 112.884646 699.2226716 112.614214 698.5603092 112.507537 696.9065125 112.241182 696.1766482 112.123633 695.2442782 111.973469 694.3361667 111.827212 693.3500061 111.668385 691.5907378 111.385043 690.6625866 111.235559 690.4600809 111.202944 690.2280431 111.165573 688.814722 110.937949 687.2178802 110.680767 685.7982308 110.452124 684.3469399 110.218384
132 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
5.5.5.2 Tie Bars According to AASHTO Guide (1993), Table 3.13 (presented in Figure 5.15), assuming a ½ inch diameter (12.7 mm or 14 mm for this particular case) the following are adopted. Therefore, 18.2 inches (462.28 mm, take 460 mm) spacing for 14 mm diameter can be adopted. Since the transverse crack spacing is 4m (13.12 feet), the spacing can easily be extracted by adding another curve for 15 inches representative slab thickness.
Figure 5.15: Recommended Maximum Tie Bar Spacing for PCC Pavements assuming ½ inch Diameter Tie Bars, Grade 40 Steel, and Subgrade Friction Factor of 1.5 (Source: AASHTO Guide, 1993) 133 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
5.5.5.3 Dowel Bars If dowels are required to be used, the size and spacing should be determined via local agency procedures and/or experience. As a general guideline, the dowel diameter should be equal to the slab thickness multiplied by 1/8 (in inches). The dowel spacing and length are normally 12 inches and 18 inches, respectively. Therefore, we need not list several tables for Dowel Bar specification. This is because, the thicknesses of the PCC Slab does not vary significantly. Therefore, assuming a 15.5 inches slab thickness to be an average value, 15.5 * (1/8) = 1.9375 inches or 49.2125 mm. This implies 50 mm diameter dowel bars of 18 inches length (457.2mm, take 460 mm) and 12 inches (1 feet or 30.48 mm) spacing.
5.6 Comparison of the Rigid Pavement Design using ERA Manual and AASHTO Guide In different sections of this research paper (Sections 1.3, 3.1, 5.1 etc), it was mentioned that ERA, Pavement Design Manual – Volume II (2002) is not a self sufficient document by itself regarding the design of rigid pavement structures. In order to forward general comments regarding its deficiency, the researchers have made extensive use of preference AASHTO, Guide for Pavement Structures – Volume I (1993) as a base platform. In order to deliver the contrast clearly and precisely, the following grand table (Table 5.53) has been presented.
134 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.53: Comparison of Rigid Pavement Design using ERA, Pavement Design Manual – Volume II (2002) and AASHTO, Guide for Pavement Structures – Volume I (1993) I. Design Considerations No.
1.
2.
3.
4.
5.
Criteria
ERA Manual, 2002
AASHTO Guide, 1993
Three of the variables here have direct and indirect numerical implication on thickness design and on slab There are no variables introduced in the design reinforcement respectively. These are: Pavement Performance procedure that can be potentially used by the designer Functional Performance – by PSI to evaluate several scenarios. Structural Performance – LS along with others Safety – Frictional Factor It is more or less similar to AASHTO when comes to the estimation of equivalency factors (Power = 4.5 – (Power = 4 – less conservative) Traffic more conservative) The Resilient Modulus (MR) of the roadbed is thoroughly studied for different seasons of the year (1 or Here, the CBR value is only used as a design input Roadbed Soil 2 measurements per month) – during wet and dry ones for better assessment of the roadbed performance. The subbase resilient modulus (ESB), concrete elastic The mechanical properties of subbase, concrete, modulus and strength (Ec, fcd, fctd), steel strength (fs) Material of Construction reinforcing steel etc are not incorporated (neither are etc are used for design. joints, load transfer joints, joint sealing properties etc) Joint sealing, load transfer devices and tie bars are analyzed further more. Environment
The effect of Temperature and Rainfall is not clearly outlined in pavement structure design
Rainfall effect in wet season is provided for by means of resilient modulus investigation to be later considered in obtaining the effective modulus of subgrade reaction 135
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
No. 6.
Type
1.
ERA Manual, 2002
AASHTO Guide, 1993
The capability of pavement structures is assessed for Its implication on the capability of pavement structures drainage and its implication in thickness design is is not assessed for design incorporated in drainage coefficient (Cd) II. Thickness Design
Drainage
No.
AAiT, SCEE
Type
Input Variables Required
ERA Manual, 2002
a. Subgrade CBR b. Cumulative Number of Equivalent Standard Axles (in million ESA or MSA)
AASHTO Guide, 1993 a. Subbase type (swelling or non swelling, plastic or not) and its resilient modulus b. Proposed economical thickness of the subbase to be used underneath the PCC slab c. Loss of Support in relation to the roadbed extent and suitability to support the PCC slab d. Depth to Rigid Foundation (the effect of bed rock with in 10 ft) e. Seasonal Resilient Roadbed Modulus f. Subbase Elastic Resilient Modulus g. Estimated Future Traffic h. Reliability i. Design Serviceability Loss j. Concrete Elastic Modulus k. Concrete Modulus of Rupture l. Load Transfer Coefficient m. Loss of Support n. Drainage Coefficient
136 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
No.
2.
3.
Type
AAiT, SCEE
ERA Manual, 2002
AASHTO Guide, 1993
Results of Thickness Design Significance
a. Here, the subbase and capping layer thicknesses are directly proportional to the subgrade CBR, whereas the PCC slabs are associated with the Design Traffic b. The design thicknesses are calculated based on a fixed combination of cumulative single axles and specific reinforcement areas (i.e. 500 mm2, 600 mm2, 700 mm2 and 800 mm2) c. The design varies from 300 mm PCC thickness of As = 500 mm2 for 175 msa (in addition to 450 mm capping layer and 150 mm subbase thickness) to 345 mm PCC thickness of As = 500 mm2 for 374 msa (in addition to 450 mm capping layer and 150 mm subbase thickness) d. Thickness values here are small (since only two parameters, i.e. design traffic and subgrade CBR are considered)
a. The subbase thickness is the designer’s preference (that is, for this study we assumed two thicknesses for comparison: 150 mm and 400 mm) b. The design thicknesses are calculated considering several variables (listed above) independent of the area of steel to be used. c. It varied from 342 mm (for assumed subbase thickness of 400 mm, CBR = 90 % and traffic of 175 msa) to 429 mm (for assumed subbase thickness of 150 mm, CBR = 2 % and traffic of 374 msa) d. Higher thicknesses resulted since several relevant variables were incorporated which in turn contributed to the lowering of effective road bed resilient modulus
Thickness Economical Implication
1. Initial Investment: since smaller thicknesses are acquired on relative terms, low initial investment is the case (though low initial investment doesn’t guarantee long term efficiency and good performance). 2. Operation Cost: relatively higher resulting in magnified frequency of maintenance and associated inconveniences
1. Initial Investment: higher one but it’s long term performance is remarkable 2. Operation Cost: reduced maintenance and rehabilitation costs in the performance period
137 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
III. Reinforcement and Joint Design No.
Type
1.
Reinforcement Design
2.
Joint Design
ERA Manual, 2002
AASHTO Guide, 1993
Here, the designers have more freedom in computing steel area (but of course there a set of guidelines to be followed) for a given thickness and length of the PCC Here, only predefined and inlflexible reinforcement slab. That is, for 25 m (longitudinal) and 4 m areas are available (500, 600, 700 and 800 mm2) (transverse) for our particular case. Variables to be considered include: length of slab in consideration, steel strength, friction factor of the interface between the slab and subbase. As per the designers estimate and preference, the following can be the ones that determine joint design: Slab dimensions in longitudinal and transverse direction, Only few general slab dimensions are given due Dowel (Load Transfer Devices) and Tie Bar attention in the general detailing provisions (i.e. slab Diameters, dimension of 25 m longitudinally for all slabs) Contraction and Expansion Joints’ specifications, Joint Sealant Properties, etc. Local experience
138 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
5.7 Flexible Pavement Design as per IRC Design Manual As mentioned in ERA, Pavement Design Manual – Volume I (2002) and AASHTO, Guide for Design of Pavement Structures (1993), cumulative number of standard axles greater than 30 million (30 msa) and 50 million (50 msa) respectively shall be addressed with special considerations. Using the ERA Flexible Pavement Design Manual is clearly impossible as the equivalent single axle load is considerably higher than the maximum provision established in ERA which is thirty million (30,000,000) equivalent single axle loads. Employing ERA Design Manual would simply mean designing a flexible pavement that cannot even last a base period of 5 years. As can be inferred from Table 5.22 or Figure 5.16, the total number of equivalent standard single axle loads will exceed thirty million before 2022 is completed. For this reason, we have turned our attention to The Indian Road Congress Design Manual (IRC 37-2001). In the code, a design CBR value (on a basis of 4 day soaking) of 2% to 10% is considered and a maximum cumulative equivalent standard axle load of one hundred fifty million (150,000,000) is provided for. [1] As can be noted from Figure 5.5 or Table 5.18, the cumulative equivalent standard single axles surpasses 150,000,000 sometime in 2035. Thus, The Indian Road Congress Design Manual (IRC 37-2001) can be successfully used to design the flexible pavement for a base period of 17 years which somehow appears weird because it is common practice to design pavements for design periods that are multiples of 5 years. Anyhow, the above finding simply means the pavement can be used substantially without the need for major rehabilitation up until the end of 2034. However, one should keep in mind that this does not mean periodic maintenance procedures are not required. But again, the IRC Manual could not fully satisfy the purpose of this research. It rather had two limitations. Even though our cumulative number of standard axles is 183 msa, the manual has provision only for standard axles up to 150 msa and This research considers soil subgrade CBR percents of: 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 20, 22, 25, 30, 31, 32, 35, 86 and 90. But the manual only provides curves for lower CBR percentages. That is from 2 to 10 only. Having pointed out the above limitations, let us now look at the strong sides that justify using the IRC Pavement Design Manual (2001). The IRC manual results in economical design since it avoids the use of stabilized interlayers compared to The British Pavement Design Manual (which may be the other option, since it has provision for esa reaching 200 million), It more or less resembles the climatic and soil conditions of Ethiopia, than the British Manual, The avoidance of stabilized inter layers results in speedy and less mechanized construction suitable to Ethiopia. 139 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Cumulative Standard Single Axles
200000000 180000000 160000000
Cumulative Equivalent Standard Single Axles
140000000 120000000 100000000 80000000 60000000 40000000 20000000 0 2015
2020
2025 Year 2030
2035
2040
Figure 5.16: Plot of Cumulative Equivalent Standard Axle LoadsVs. Year The following tables illustrate the appropriate design for 17 years design period and different classes of subgrade CBR. This design approach is also on the principle of stage construction whereby the rest of the 23 design years are to be addressed through major rehabilitation procedures to be executed every 5 or 10 years.
Table 5.54: Flexible Pavement Design for CBR 2 % and 17 Years Design Period
Design Manual: Indian Road Congress: IRC 37-2001 Design Period = 17 years Design CBR= 2% Design Traffic = 147586852.9 esa
50mm Asphalt Concrete 215 mm Dense Bitumen Macadam
250 mm Granular Base Course
460 mm Sub-base
140 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.55: Flexible Pavement Design for CBR 3 % and 17 Years Design Period
Design Manual: Indian Road Congress: IRC 37-2001 Design Period = 17 years Design CBR = 3 % Design Traffic = 147586852.9 esa
50mm Asphalt Concrete 210 mm Dense Bitumen Macadam
250 mm Granular Base Course
380 mm Sub-base
Table 5.56: Flexible Pavement Design for CBR 4 % and 17 Years Design Period
Design Manual: Indian Road Congress: IRC 37-2001 Design Period = 17 years Design CBR = 4 % Design Traffic = 147586852.9 esa
50mm Asphalt Concrete 190 mm Dense Bitumen Macadam
250 mm Granular Base Course
330 mm Sub-base
141 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.57: Flexible Pavement Design for CBR 5 % and 17 Years Design Period
Design Manual: Indian Road Congress: IRC 37-2001 Design Period = 17 years Design CBR = 5 % Design Traffic = 147586852.9 esa
50mm Asphalt Concrete 170 mm Dense Bitumen Macadam
250 mm Granular Base Course
300 mm Sub-base
Table 5.58: Flexible Pavement Design for CBR 6 % and 17 Years Design Period
Design Manual: Indian Road Congress: IRC 37-2001 Design Period = 17 years Design CBR = 6 % Design Traffic = 147586852.9 esa
50mm Asphalt Concrete 160 mm Dense Bitumen Macadam
250 mm Granular Base Course
260 mm Sub-base
142 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.59: Flexible Pavement Design for CBR 7 % and 17 Years Design Period
Design Manual: Indian Road Congress: IRC 37-2001 Design Period = 17 years Design CBR = 7 % Design Traffic = 147586852.9 esa
50mm Asphalt Concrete 165 mm Dense Bitumen Macadam
250 mm Granular Base Course
230 mm Sub-base
Table 5.60: Flexible Pavement Design for CBR 8 % and 17 Years Design Period
Design Manual: Indian Road Congress: IRC 37-2001 Design Period = 17 years Design CBR = 8% Design Traffic = 147586852.9 esa
50mm Asphalt Concrete 160 mm Dense Bitumen Macadam
250 mm Granular Base Course
200 mm Sub-base
143 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.61: Flexible Pavement Design for CBR 9 % and 17 Years Design Period
Design Manual: Indian Road Congress: IRC 37-2001 Design Period = 17 years Design CBR = 9 % Design Traffic = 147586852.9 esa
50mm Asphalt Concrete 155 mm Dense Bitumen Macadam
250 mm Granular Base Course
200 mm Sub-base
Table 5.62: Flexible Pavement Design for CBR 10 % and 17 Years Design Period
Design Manual: Indian Road Congress: IRC 37-2001 Design Period = 17 years Design CBR = 10 % Design Traffic = 147586852.9 esa
50mm Asphalt Concrete 150 mm Dense Bitumen Macadam
250 mm Granular Base Course
200 mm Sub-base
144 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
5.7.1 Flexible Pavement Design Adjustment Slight modifications to the thicknesses of the asphalt concrete and that of the dense bitumen macadam can be made. Since dense bitumen macadams have relatively lesser quality than asphaltic concretes, increasing the thicknesses of the asphalt concrete by 10mm and decreasing the thicknesses of the dense bitumen macadam proportionally could enhance the performance of the pavement. That is, the wearing course will have more resistance to deformations, sufficient stiffness to reduce the stresses transmitted to the underlying pavement layers and will have good durability. In addition, this modification is good for ease of construction and quality control to overcome workmanship problems during construction. [1]
5.7.2 Pavement Materials Specification The technical specification of flexible pavement constituents such as sub-base and granular base course shall be determined as outlined in ERA Design Manual, 2002, Standard Technical Specifications, 05-Series 5000. For Bituminous materials, 06-Series 6000 shall be reviewed.
5.8 Alternative Design While designing a major rural trunk road pavement structure for the anticipated cumulative number of equivalent standard axles (ESA), it is wise to see whether a single lane can accommodate the traffic flow at the end of the design year without any sort of inconvenience. That is, the strength and resistance of the pavement are not the only requirements to be met by the designer, but additional design parameters shall also be considered for better highway operation. Among the major factors to be considered, the following are a few of them. Movement with the Design Speed (V): that is without any sort of traffic jam or congestion of overall traffic induced by slow moving trucks and truck-trailers, Providing Stopping and Passing Sight Distances: especially when we look for two-lane, two-way rural road way (that is our basic road type), adequate values of these may not be ascertained due to limitations Improving Surface Performance: by this, we reduce the future anticipated maintenance frequency and effort in meeting the required standards of operation. Therefore, the researchers of this study have made their decision to come up with certain alternative design of the pavement structure for the segment chosen. And so, for the above mentioned reasons, a four-lane, two-way rural roadway is assumed to be taken for the segment from Adama (Nazareth) to Awash. This is a justified geometric measure to improve overall road and traffic performance. Additionally, this measure is believed to give solutions to the following problems which are naturally associated with heavily trafficked two-lane, two-way rural roadways: 145 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
One, brutal accidents may frequently occur as cars and small buses attempt to pass slowly moving trucks and truck-trailers, Two, the traffic may not attain the required mobility at the design speed on the segment, Three, only one line may be heavily trafficked, thus, leading to visible roadway failures along that particular line and We shall consider the advantages and disadvantages of a four-lane, two-way rural roadways for similar pavement alternatives with its two-lane, two-way rural roadways counterpart. In doing so, the cumulative number of standard axles shall be obtained for the four-lane, two-way alternative of the roadway segment. According to Table 2.4 of ERA, Pavement Design Manual – Volume II (2002), a lane distribution factor of 80 % to 100 % is recommended. But, since our purpose is to deal with smaller traffic, we may take lane distribution factor, DL = 0.8. Therefore, the following table (Table 5.63) can be referred (for flexible and rigid pavements): Table 5.63: Cumulative Number of Standard Axles for Different Design Years of the Four-Lane, Two-Way Proposed Road Roadway Pavement Type Alternative 2 Lane 2 Way Rural Roadway
20
25
30
35
40
Cum. ESA* 175226264.8 198410079 251296925 309688275 374157044 Rigid Pavement Cum. MSA** 175 198 251 310 374 Flexible Pavement
Rigid 4 Lane 2 Pavement Way Rural Roadway Flexible Pavement
Cum. ESA
183823225.9
--
--
--
--
Cum. MSA
183
--
--
--
--
Cum. ESA
140181011.8 158728063 201037540 247750620 299325635
Cum. MSA
140
159
201
247
299
Cum. ESA
147058580.7
--
--
--
--
Cum. MSA
147
--
--
--
--
* Cumulative Number of Equivalent Standard Axles ** Cumulative Number of Million Equivalent Standard Axles
5.8.1 Rigid Pavement Alternative For the design of rigid pavement structures of the four-lane, two-way rural roadway, we shall redesign the pavement with reduced traffic volume based on the lane distribution factor considered.
146 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
5.8.1.1 Thickness Design Tables 5.64 and 5.65 illustrate the thickness design of the four-lane, two-way road way for two subbase cases (150 mm of granular subbase material without capping layer and 400 mm thick subbase with capping layer of equivalent thickness) for different design periods (20, 25, 30, 35 and 40 years). All the mm thickness values in the following table shall be rounded off to the next higher 5 mm value for the sake of site applicability. That is: 376.42 mm will be rounded off to 380 mm.
147 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.64: Cumulative Number of Standard Axles of the Four-Lane, Two-Way Proposed Road (150 mm subbase thickness) 140 msa
Soil Subgrade CBR (%)
k (pci)
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
43.5 53 60 66 75.5 81.75 89 98 108 120 125 138 144 152 160 169 186 195.5 197.5 200 215 233 250 268
D (inches) 14.68398 14.62725 14.58985 14.56015 14.5167 14.4901 14.46085 14.4269 14.3915 14.3518 14.33608 14.29705 14.2795 14.25765 14.23623 14.213 14.17124 14.1489 14.14425 14.13855 14.10525 14.06725 14.03305 13.9985
159 msa
D (mm) D (inches) 372.9731 14.9556 371.5322 14.8989 370.5822 14.8615 369.8278 14.8318 368.7242 14.7884 368.0485 14.7618 367.3056 14.7325 366.4433 14.6986 365.5441 14.6632 364.5357 14.6235 364.1364 14.6077 363.1451 14.5687 362.6993 14.5512 362.1443 14.5293 361.6002 14.5079 361.0102 14.4847 359.9495 14.4429 359.3821 14.4206 359.264 14.4159 359.1192 14.4102 358.2734 14.3769 357.3082 14.3389 356.4395 14.3047 355.5619 14.2702
201 msa
D (mm) D (inches) 379.873 15.4685 378.432 15.4117 377.482 15.3743 376.728 15.3446 375.624 15.3012 374.949 15.2746 374.206 15.2453 373.343 15.2114 372.444 15.176 371.436 15.1363 371.037 15.1206 370.045 15.0815 369.599 15.064 369.044 15.0421 368.5 15.0207 367.91 14.9975 366.85 14.9557 366.282 14.9334 366.164 14.9287 366.019 14.923 365.174 14.8897 364.208 14.8517 363.34 14.8175 362.462 14.783
D (mm) 392.899 391.458 390.508 389.753 388.65 387.974 387.231 386.369 385.47 384.461 384.062 383.071 382.625 382.07 381.526 380.936 379.875 379.308 379.189 379.045 378.199 377.234 376.365 375.487
247 msa D (inches) 15.933 15.8763 15.8389 15.8092 15.7657 15.7391 15.7099 15.6759 15.6405 15.6008 15.5851 15.5461 15.5285 15.5067 15.4853 15.462 15.4203 15.3979 15.3933 15.3876 15.3543 15.3163 15.2821 15.2475
299 msa
D (mm) D (inches) 404.698 16.3755 403.257 16.3187 402.307 16.2813 401.553 16.2516 400.449 16.2082 399.774 16.1816 399.031 16.1523 398.168 16.1184 397.269 16.083 396.261 16.0433 395.862 16.0276 394.87 15.9885 394.424 15.971 393.869 15.9491 393.325 15.9277 392.735 15.9045 391.675 15.8627 391.107 15.8404 390.989 15.8357 390.844 15.83 389.998 15.7967 389.033 15.7587 388.165 15.7245 387.287 15.69
D (mm) 415.936 414.495 413.546 412.791 411.688 411.012 410.269 409.407 408.507 407.499 407.1 406.108 405.663 405.108 404.564 403.974 402.913 402.345 402.227 402.083 401.237 400.271 399.403 398.525 148
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.65: Cumulative Number of Standard Axles of the Four-Lane, Two-Way Proposed Road (400 mm combined subbase thickness) 140 msa
Soil Subgrade CBR (%)
k (pci)
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
78.37 95.623 119.983 160.583 182.913 201.183 214.378 221.483 271.218 282.383 294.563 302.683 318.923 333.133 388.958 404.183 439.708 500.608 525.983 549.328 759.433 850.783 1114.68 1206.03
D (inches) 14.5043 14.4357 14.3519 14.2347 14.1785 14.1359 14.1066 14.0913 13.9925 13.9719 13.9501 13.9358 13.9081 13.8845 13.7976 13.7752 13.7251 13.6446 13.6129 13.5845 13.356 13.2682 13.0405 12.9685
159 msa
D (mm) D (inches) 368.409 14.7758 366.666 14.7071 364.537 14.6233 361.561 14.5062 360.135 14.45 359.051 14.4073 358.308 14.3781 357.92 14.3628 355.408 14.2639 354.886 14.2434 354.332 14.2216 353.969 14.2073 353.264 14.1795 352.666 14.156 350.458 14.069 349.89 14.0467 348.619 13.9966 346.573 13.9161 345.768 13.8844 345.045 13.8559 339.241 13.6274 337.011 13.5396 331.228 13.3119 329.401 13.24
201 msa
D (mm) D (inches) 375.304 15.2882 373.561 15.2195 371.432 15.1357 368.457 15.0186 367.03 14.9624 365.946 14.9197 365.203 14.8905 364.815 14.8752 362.304 14.7763 361.781 14.7558 361.227 14.734 360.865 14.7197 360.16 14.6919 359.561 14.6684 357.353 14.5814 356.785 14.5591 355.514 14.509 353.468 14.4285 352.663 14.3968 351.941 14.3683 346.136 14.1398 343.906 14.052 338.123 13.8243 336.296 13.7524
247 msa
D (mm) D (inches) 388.319 15.7524 386.576 15.6837 384.448 15.5999 381.472 15.4828 380.046 15.4266 378.961 15.3839 378.218 15.3547 377.83 15.3394 375.319 15.2405 374.796 15.22 374.243 15.1982 373.88 15.1839 373.175 15.1561 372.576 15.1326 370.369 15.0456 369.801 15.0233 368.529 14.9732 366.483 14.8927 365.678 14.861 364.956 14.8325 359.152 14.604 356.922 14.5162 351.138 14.2885 349.311 14.2166
299 msa
D (mm) D (inches) 400.11 16.1944 398.367 16.1258 396.238 16.042 393.262 15.9248 391.836 15.8687 390.752 15.826 390.009 15.7967 389.621 15.7815 387.109 15.6826 386.587 15.662 386.033 15.6402 385.67 15.6259 384.965 15.5982 384.367 15.5746 382.159 15.4877 381.591 15.4653 380.32 15.4153 378.274 15.3347 377.469 15.303 376.746 15.2746 370.942 15.0461 368.712 14.9583 362.929 14.7306 361.102 14.6586
D (mm) 411.338 409.595 407.466 404.49 403.064 401.98 401.237 400.849 398.337 397.815 397.261 396.898 396.194 395.595 393.387 392.819 391.548 389.502 388.697 387.974 382.17 379.94 374.157 372.33 149
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
5.8.1.2 Slab Reinforcement Design According to AASHTO Guide (1993), the area of reinforcement can be obtained as percentage of the slab. Taking slab lengths of 25 m (82.021 ft) and 4 m (13.12 ft) in the longitudinal and transverse directions, the total amount can be found. From Section 5.5.5, we may recall: As % = (82.021 ft * 1.5) / (2 * 37836 psi) = 0.1661 % for Longitudinal Bars & As % = (13.12 ft * 1.5) / (2 * 37836 psi) = 0.02675 % for Transverse Bars Tables 5.66: Reinforcement Computation of the PCC Slabs for 400 mm Subbase Thickness in Longitudinal (Short) and Transverse (Long) Directions – 140 msa Soil Subgrade CBR (%) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
k (pci) 78.37 95.623 119.983 160.583 182.913 201.183 214.378 221.483 271.218 282.383 294.563 302.683 318.923 333.133 388.958 404.183 439.708 500.608 525.983 549.328 759.433 850.783 1114.68 1206.03
D (inches) D (m) 14.5043 0.36840922 14.4357 0.36666678 14.3519 0.36453826 14.2347 0.36156138 14.1785 0.3601339 14.1359 0.35905186 14.1066 0.35830764 14.0913 0.35791902 13.9925 0.3554095 13.9719 0.35488626 13.9501 0.35433254 13.9358 0.35396932 13.9081 0.35326574 13.8845 0.3526663 13.7976 0.35045904 13.7752 0.34989008 13.7251 0.34861754 13.6446 0.34657284 13.6129 0.34576766 13.5845 0.3450463 13.356 0.3392424 13.2682 0.33701228 13.0405 0.3312287 12.9685 0.3293999
Longitudinal (mm2/m) 611.917399 609.0232549 605.4878428 600.5433285 598.1723242 596.375086 595.1389574 594.4934705 590.325228 589.456141 588.5364276 587.9331294 586.7645027 585.7688496 582.1026526 581.157626 579.0439726 575.6477832 574.3104018 573.112243 563.4721276 559.7679607 550.1615963 547.1240107
Transverse (mm2/m) 98.5531504 98.0870303 97.5176299 96.7212848 96.3394196 96.0499631 95.8508768 95.746917 95.0755953 94.9356234 94.7874978 94.6903328 94.5021181 94.3417619 93.7512978 93.5990953 93.2586781 92.7117004 92.4963067 92.3033357 90.7507344 90.154155 88.6069895 88.1177672
150 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Tables 5.67: Reinforcement Computation of the PCC Slabs for 400 mm Subbase Thickness in Longitudinal (Short) and Transverse (Long) Directions – 159 msa Soil Subgrade CBR (%) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
k (pci) 78.37 95.623 119.983 160.583 182.913 201.183 214.378 221.483 271.218 282.383 294.563 302.683 318.923 333.133 388.958 404.183 439.708 500.608 525.983 549.328 759.433 850.783 1114.68 1206.03
D (inches) D (m) 14.7758 0.37530532 14.7071 0.37356034 14.6233 0.37143182 14.5062 0.36845748 14.45 0.36703 14.4073 0.36594542 14.3781 0.36520374 14.3628 0.36481512 14.2639 0.36230306 14.2434 0.36178236 14.2216 0.36122864 14.2073 0.36086542 14.1795 0.3601593 14.156 0.3595624 14.069 0.3573526 14.0467 0.35678618 13.9966 0.35551364 13.9161 0.35346894 13.8844 0.35266376 13.8559 0.35193986 13.6274 0.34613596 13.5396 0.34390584 13.3119 0.33812226 13.24 0.336296
Longitudinal (mm2/m) 623.371628 620.4732651 616.9378529 611.9975575 609.6265532 607.8250961 606.5931864 605.9476995 601.7752382 600.9103701 599.9906566 599.3873584 598.2145128 597.2230787 593.5526627 592.611855 590.4982017 587.1020122 585.7646308 584.5622531 574.9221378 571.2179709 561.6116064 558.5782397
Transverse (mm2/m) 100.397926 99.9311266 99.3617262 98.5660605 98.1841953 97.8940593 97.6956525 97.5916928 96.9196916 96.7803991 96.6322735 96.5351085 96.3462143 96.1865376 95.595394 95.443871 95.1034538 94.5564761 94.3410824 94.1474319 92.5948307 91.9982513 90.4510858 89.962543
Tables 5.68: Reinforcement Computation of the PCC Slabs for 400 mm Subbase Thickness in Longitudinal (Short) and Transverse (Long) Directions – 201 msa Soil Subgrade CBR (%) 2 3 4 5 6 7 8 9 10 11
k (pci) 78.37 95.623 119.983 160.583 182.913 201.183 214.378 221.483 271.218 282.383
D (inches) D (m) 15.2882 0.38832028 15.2195 0.3865753 15.1357 0.38444678 15.0186 0.38147244 14.9624 0.38004496 14.9197 0.37896038 14.8905 0.3782187 14.8752 0.37783008 14.7763 0.37531802 14.7558 0.37479732
Longitudinal (mm2/m) 644.9891121 642.0907492 638.5553371 633.6150416 631.2440373 629.4425803 628.2106706 627.5651836 623.3927223 622.5278542
Transverse (mm2/m) 103.879558 103.412759 102.843358 102.047692 101.665827 101.375691 101.177284 101.073325 100.401324 100.262031 151
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
12 13 14 15 16 20 22 25 30 31 32 35 86 90
294.563 302.683 318.923 333.133 388.958 404.183 439.708 500.608 525.983 549.328 759.433 850.783 1114.68 1206.03
14.734 14.7197 14.6919 14.6684 14.5814 14.5591 14.509 14.4285 14.3968 14.3683 14.1398 14.052 13.8243 13.7524
0.3742436 0.37388038 0.37317426 0.37257736 0.37036756 0.36980114 0.3685286 0.3664839 0.36567872 0.36495482 0.35915092 0.3569208 0.35113722 0.34931096
AAiT, SCEE
621.6081408 621.0048425 619.831997 618.8405628 615.1701469 614.2293391 612.1156858 608.7194964 607.3821149 606.1797373 596.5396219 592.835455 583.2290906 580.1957239
100.113905 100.01674 99.8278463 99.6681696 99.077026 98.925503 98.5850858 98.0381081 97.8227144 97.6290639 96.0764626 95.4798832 93.9327177 93.4441749
Tables 5.69: Reinforcement Computation of the PCC Slabs for 400 mm Subbase Thickness in Longitudinal (Short) and Transverse (Long) Directions – 247 msa Soil Subgrade CBR (%) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
k (pci) 78.37 95.623 119.983 160.583 182.913 201.183 214.378 221.483 271.218 282.383 294.563 302.683 318.923 333.133 388.958 404.183 439.708 500.608 525.983 549.328 759.433 850.783 1114.68 1206.03
D (inches) D (m) 15.7524 0.40011096 15.6837 0.39836598 15.5999 0.39623746 15.4828 0.39326312 15.4266 0.39183564 15.3839 0.39075106 15.3547 0.39000938 15.3394 0.38962076 15.2405 0.3871087 15.22 0.386588 15.1982 0.38603428 15.1839 0.38567106 15.1561 0.38496494 15.1326 0.38436804 15.0456 0.38215824 15.0233 0.38159182 14.9732 0.38031928 14.8927 0.37827458 14.861 0.3774694 14.8325 0.3767455 14.604 0.3709416 14.5162 0.36871148 14.2885 0.3629279 14.2166 0.36110164
Longitudinal (mm2/m) 664.5731015 661.6747385 658.1393264 653.199031 650.8280266 649.0265696 647.7946599 647.149173 642.9767117 642.1118435 641.1921301 640.5888319 639.4159863 638.4245521 634.7541362 633.8133284 631.6996751 628.3034857 626.9661043 625.7637266 616.1236112 612.4194444 602.8130799 599.7797132
Transverse (mm2/m) 107.033683 106.566883 105.997483 105.201817 104.819952 104.529816 104.331409 104.22745 103.555448 103.416156 103.26803 103.170865 102.981971 102.822294 102.231151 102.079628 101.739211 101.192233 100.976839 100.783189 99.2305874 98.634008 97.0868425 96.5982997 152
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Tables 5.70: Reinforcement Computation of the PCC Slabs for 400 mm Subbase Thickness in Longitudinal (Short) and Transverse (Long) Directions – 299 msa Soil Subgrade CBR (%) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
k (pci) 78.37 95.623 119.983 160.583 182.913 201.183 214.378 221.483 271.218 282.383 294.563 302.683 318.923 333.133 388.958 404.183 439.708 500.608 525.983 549.328 759.433 850.783 1114.68 1206.03
D (inches) D (m) 16.1944 0.41133776 16.1258 0.40959532 16.042 0.4074668 15.9248 0.40448992 15.8687 0.40306498 15.826 0.4019804 15.7967 0.40123618 15.7815 0.4008501 15.6826 0.39833804 15.662 0.3978148 15.6402 0.39726108 15.6259 0.39689786 15.5982 0.39619428 15.5746 0.39559484 15.4877 0.39338758 15.4653 0.39281862 15.4153 0.39154862 15.3347 0.38950138 15.303 0.3886962 15.2746 0.38797484 15.0461 0.38217094 14.9583 0.37994082 14.7306 0.37415724 14.6586 0.37232844
Longitudinal (mm2/m) 683.2205019 680.3263579 676.7909457 671.8464314 669.479646 667.6781889 666.4420604 665.8007923 661.628331 660.759244 659.8395306 659.2362323 658.0676056 657.0719526 653.4057555 652.4607289 650.3512945 646.9508861 645.6135047 644.4153459 634.7752306 631.0710637 621.4646992 618.4271136
Transverse (mm2/m) 110.036964 109.570844 109.001444 108.205098 107.823913 107.533777 107.334691 107.23141 106.559409 106.419437 106.271312 106.174147 105.985932 105.825576 105.235112 105.082909 104.743171 104.195514 103.98012 103.787149 102.234548 101.637969 100.090803 99.601581
Tables 5.71: Reinforcement Computation of the PCC Slabs for 150 mm Subbase Thickness in Longitudinal (Short) and Transverse (Long) Directions – 140 msa Soil Subgrade CBR (%) 2 3 4 5 6 7 8 9 10 11
k (pci) 43.5 53 60 66 75.5 81.75 89 98 108 120
D (inches) 14.68398 14.62725 14.58985 14.56015 14.5167 14.4901 14.46085 14.4269 14.3915 14.3518
D (m) 0.37297309 0.37153215 0.37058219 0.36982781 0.36872418 0.36804854 0.36730559 0.36644326 0.3655441 0.36453572
Longitudinal (mm2/m) 619.4978626 617.1044982 615.5266413 614.2736372 612.4405387 611.3183196 610.0843004 608.6519944 607.1585149 605.4836239
Transverse (mm2/m) 99.7740318 99.3885654 99.1344416 98.9326375 98.6374054 98.4566649 98.2579184 98.0272365 97.7867022 97.5169505 153
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
12 13 14 15 16 20 22 25 30 31 32 35 86 90
125 138 144 152 160 169 186 195.5 197.5 200 215 233 250 268
14.33608 14.29705 14.2795 14.25765 14.23623 14.213 14.17124 14.1489 14.14425 14.13855 14.10525 14.06725 14.03305 13.9985
0.36413643 0.36314507 0.3626993 0.36214431 0.36160024 0.3610102 0.3599495 0.35938206 0.35926395 0.35911917 0.35827335 0.35730815 0.35643947 0.3555619
AAiT, SCEE
604.8204177 603.1737932 602.4333817 601.5115589 600.6078772 599.6278339 597.8660343 596.923539 596.7273616 596.486886 595.0820027 593.4788325 592.0359794 590.5783602
97.4101369 97.1449377 97.0256897 96.8772244 96.7316807 96.5738386 96.2900897 96.1382949 96.1066993 96.0679692 95.8417039 95.5835032 95.3511226 95.1163639
Tables 5.72: Reinforcement Computation of the PCC Slabs for 150 mm Subbase Thickness in Longitudinal (Short) and Transverse (Long) Directions – 159 msa Soil Subgrade CBR (%) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
k (pci) D (inches) 43.5 14.9556 53 14.8989 60 14.8615 66 14.8318 75.5 14.7884 81.75 14.7618 89 14.7325 98 14.6986 108 14.6632 120 14.6235 125 14.6077 138 14.5687 144 14.5512 152 14.5293 160 14.5079 169 14.4847 186 14.4429 195.5 14.4206 197.5 14.4159 200 14.4102 215 14.3769 233 14.3389 250 14.3047 268 14.2702
D (m) 0.37987224 0.37843206 0.3774821 0.37672772 0.37562536 0.37494972 0.3742055 0.37334444 0.37244528 0.3714369 0.37103558 0.37004498 0.36960048 0.36904422 0.36850066 0.36791138 0.36684966 0.36628324 0.36616386 0.36601908 0.36517326 0.36420806 0.36333938 0.36246308
Longitudinal (mm2/m) 630.9571542 628.5650556 626.9871986 625.7341945 623.9032054 622.7809863 621.5448577 620.1146612 618.6211816 616.9462907 616.2797094 614.6343505 613.8960485 612.9721162 612.0692782 611.0905007 609.3270135 608.3862057 608.1879189 607.9474433 606.54256 604.9393898 603.4965367 602.0410269
Transverse (mm2/m) 101.619623 101.23436 100.980237 100.778432 100.48354 100.3028 100.103713 99.8733711 99.6328369 99.3630851 99.255728 98.9907326 98.8718244 98.7230193 98.5776116 98.4199733 98.1359525 97.9844295 97.9524942 97.9137641 97.6874988 97.4292981 97.1969175 96.9624985 154
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Tables 5.73: Reinforcement Computation of the PCC Slabs for 150 mm Subbase Thickness in Longitudinal (Short) and Transverse (Long) Directions – 201 msa Soil Subgrade CBR (%) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
k (pci) D (inches) 43.5 15.4685 53 15.4117 60 15.3743 66 15.3446 75.5 15.3012 81.75 15.2746 89 15.2453 98 15.2114 108 15.176 120 15.1363 125 15.1206 138 15.0815 144 15.064 152 15.0421 160 15.0207 169 14.9975 186 14.9557 195.5 14.9334 197.5 14.9287 200 14.923 215 14.8897 233 14.8517 250 14.8175 268 14.783
D (m) 0.3928999 0.39145718 0.39050722 0.38975284 0.38865048 0.38797484 0.38723062 0.38636956 0.3854704 0.38446202 0.38406324 0.3830701 0.3826256 0.38206934 0.38152578 0.3809365 0.37987478 0.37930836 0.37918898 0.3790442 0.37819838 0.37723318 0.3763645 0.3754882
Longitudinal (mm2/m) 652.5957327 650.1994152 648.6215582 647.3685542 645.5375651 644.4153459 643.1792174 641.7490208 640.2555412 638.5806503 637.9182879 636.2687101 635.5304081 634.6064758 633.7036379 632.7248603 630.9613731 630.0205653 629.8222785 629.581803 628.1769196 626.5737495 625.1308963 623.6753865
Transverse (mm2/m) 105.104652 104.71871 104.464586 104.262782 103.96789 103.787149 103.588063 103.357721 103.117187 102.847435 102.740757 102.475082 102.356174 102.207369 102.061961 101.904323 101.620302 101.468779 101.436844 101.398114 101.171849 100.913648 100.681267 100.446848
Tables 5.74: Reinforcement Computation of the PCC Slabs for 150 mm Subbase Thickness in Longitudinal (Short) and Transverse (Long) Directions – 247 msa Soil Subgrade CBR (%) 2 3 4 5 6 7 8 9 10 11
k (pci) D (inches) 43.5 15.933 53 15.8763 60 15.8389 66 15.8092 75.5 15.7657 81.75 15.7391 89 15.7099 98 15.6759 108 15.6405 120 15.6008
D (m) 0.4046982 0.40325802 0.40230806 0.40155368 0.40044878 0.39977314 0.39903146 0.39816786 0.3972687 0.39626032
Longitudinal (mm2/m) 672.1923787 669.80028 668.222423 666.969419 665.134211 664.0119919 662.7800822 661.3456668 659.8521872 658.1772962
Transverse (mm2/m) 108.260815 107.875553 107.621429 107.419625 107.124053 106.943313 106.744906 106.513884 106.27335 106.003598 155
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
12 13 14 15 16 20 22 25 30 31 32 35 86 90
125 138 144 152 160 169 186 195.5 197.5 200 215 233 250 268
15.5851 15.5461 15.5285 15.5067 15.4853 15.462 15.4203 15.3979 15.3933 15.3876 15.3543 15.3163 15.2821 15.2475
0.39586154 0.39487094 0.3944239 0.39387018 0.39332662 0.3927348 0.39167562 0.39110666 0.39098982 0.39084504 0.38999922 0.38903402 0.38816534 0.3872865
AAiT, SCEE
657.5149338 655.869575 655.127054 654.2073406 653.3045027 652.3215062 650.5622379 649.6172113 649.4231433 649.1826678 647.7777844 646.1746143 644.7317611 643.2720325
105.896921 105.631925 105.512337 105.364212 105.218804 105.060486 104.777145 104.624943 104.593687 104.554957 104.328691 104.070491 103.83811 103.603012
Tables 5.75: Reinforcement Computation of the PCC Slabs for 150 mm Subbase Thickness in Longitudinal (Short) and Transverse (Long) Directions – 299 msa Soil Subgrade CBR (%) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
k (pci) D (inches) 43.5 16.3755 53 16.3187 60 16.2813 66 16.2516 75.5 16.2082 81.75 16.1816 89 16.1523 98 16.1184 108 16.083 120 16.0433 125 16.0276 138 15.9885 144 15.971 152 15.9491 160 15.9277 169 15.9045 186 15.8627 195.5 15.8404 197.5 15.8357 200 15.83 215 15.7967 233 15.7587 250 15.7245 268 15.69
D (m) 0.4159377 0.41449498 0.41354502 0.41279064 0.41168828 0.41101264 0.41026842 0.40940736 0.4085082 0.40749982 0.40710104 0.4061079 0.4056634 0.40510714 0.40456358 0.4039743 0.40291258 0.40234616 0.40222678 0.402082 0.40123618 0.40027098 0.3994023 0.398526
Longitudinal (mm2/m) 690.8608734 688.4645559 686.886699 685.6336949 683.8027058 682.6804867 681.4443581 680.0141616 678.520682 676.845791 676.1834286 674.5338509 673.7955488 672.8716165 671.9687786 670.990001 669.2265138 668.2857061 668.0874192 667.8469437 666.4420604 664.8388902 663.396037 661.9405273
Transverse (mm2/m) 111.267494 110.881552 110.627428 110.425624 110.130732 109.949991 109.750905 109.520563 109.280029 109.010277 108.903599 108.637924 108.519016 108.370211 108.224803 108.067165 107.783144 107.631621 107.599686 107.560956 107.334691 107.07649 106.844109 106.60969 156
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
5.8.2 Flexible Pavement Alternative Design Recalling from Table 5.22, the design cumulative equivalent standard single axles at the end of the base period was 183823226. Introducing a lane distribution factor of 0.8, the new number of equivalent standard single axle becomes 183823226*0.8=147058580.8. Therefore, the IRC Pavement Design Manual (2001) can be successfully used to design the roadway for a base period of 20 years. This approach makes more sense since such major trunk roads should be designed for as long a base period as possible in order to avoid regular major rehabilitation activities which could severely interfere with traffic flow. Additionally, reasons mentioned in Section 5.8 serve as further justifying points for this approach. This way it is possible to avoid regular inconveniences. Table 5.76: Flexible Pavement Design for CBR 2% and 20 Years Design Period Design Manual: Indian Road Congress: IRC 37-2001 Design Period=20 years Design CBR=2% Design Traffic=147058580.8esa
50mm Asphalt Concrete 215 mm Dense Bitumen Macadam
250 mm Granular Base Course
460 mm Sub-base
Table 5.77: Flexible Pavement Design for CBR 3% and 20 Years Design Period Design Manual: Indian Road Congress: IRC 37-2001 Design Period=20 years Design CBR=3% Design Traffic=147058580.8esa
50mm Asphalt Concrete 210 mm Dense Bitumen Macadam
250 mm Granular Base Course
380 mm Sub-base
157 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.78: Flexible Pavement Design for CBR 4% and 20 Years Design Period
Design Manual: Indian Road Congress: IRC 37-2001 Design Period=20 years Design CBR=4% Design Traffic=147058580.8esa
50mm Asphalt Concrete 190 mm Dense Bitumen Macadam
250 mm Granular Base Course
330 mm Sub-base
Table 5.79: Flexible Pavement Design for CBR 5% and 20 Years Design Period
Design Manual: Indian Road Congress: IRC 37-2001 Design Period=20 years Design CBR=5% Design Traffic=147058580.8esa
50mm Asphalt Concrete 170 mm Dense Bitumen Macadam
250 mm Granular Base Course
300 mm Sub-base
158 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.80: Flexible Pavement Design for CBR 6% and 20 Years Design Period
Design Manual: Indian Road Congress: IRC 37-2001 Design Period=20 years Design CBR=6% Design Traffic=147058580.8esa
50mm Asphalt Concrete 160 mm Dense Bitumen Macadam
250 mm Granular Base Course
260 mm Sub-base
Table 5.81: Flexible Pavement Design for CBR 7% and 20 Years Design Period
Design Manual: Indian Road Congress: IRC 37-2001 Design Period=20 years Design CBR=7% Design Traffic=147058580.8esa
50mm Asphalt Concrete 165 mm Dense Bitumen Macadam
250 mm Granular Base Course
230 mm Sub-base
159 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.82: Flexible Pavement Design for CBR 8% and 20 Years Design Period
Design Manual: Indian Road Congress: IRC 37-2001 Design Period=20 years Design CBR=8% Design Traffic=147058580.8esa
50mm Asphalt Concrete 160 mm Dense Bitumen Macadam
250 mm Granular Base Course
200 mm Sub-base
Table 5.83: Flexible Pavement Design for CBR 9% and 20 Years Design Period
Design Manual: Indian Road Congress: IRC 37-2001 Design Period=20 years Design CBR=9% Design Traffic=147058580.8esa
50mm Asphalt Concrete 155 mm Dense Bitumen Macadam
250 mm Granular Base Course
200 mm Sub-base
160 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
12Table 5.84: Flexible Pavement Design for CBR 10% and 20 Years Design Period
Design Manual: Indian Road Congress: IRC 37-2001 Design Period=20 years Design CBR=10% Design Traffic=147058580.8esa
50mm Asphalt Concrete 150 mm Dense Bitumen Macadam
250 mm Granular Base Course
200 mm Sub-base
5.9 Unit Rate Analysis The general essence of this research is the implication of rigid pavements construction in Ethiopia and, among other things, it is necessary to make economic comparison. For this comparison unit rate analysis is carried out. The earthwork in a roadway project (either a flexible pavement or a rigid one) is more of less the same. The only major difference comes at the construction of the pavement structure layers (i.e. subbase to surfacing). Therefore, comparing the expense of each pavement alternative with one another gives a good indication on whether constructing rigid pavements is feasible or not. Unit rates are usually a combination of rates for labor, equipment and materials which are the direct cost and the indirect one will be taken as the percentage of this. [16] Thus, 30 % percent is used for our case. The challenge here is that current market rates paid for labor near the site and market prices for equipment hire. Nonetheless, the researchers have tried to come up with a reasonable rate for each item based on data from previous years. Appendix D carries the cost breakdown carried for the purpose of the study.
5.9.1 Labor Rates The formula used to estimate labor rates is given by: Hourly Rate (
Birr monthly cost of employing an operative )= hr actual hours worked per month
Then this hourly rate is divided by the hourly output of the labor force to get output rates. Spreadsheets are used for these repetitious calculations for various combinations are tried. 161 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
The following breakdown was used for labor rate calculation. 1. Asphalt Concrete a. Wearing and Binding Course Paver Operator Roller Operator Foreman Helper b. Prime Coat Bitumen Distributor Operator Helper c. Tack Coat Bitumen Distributor Operator Helper 2. Cement Concrete a. Foreman b. Gang Leader c. Daily Laborer d. Helper e. Mixer Operator
5.9.2 Material Rates [16] Quotations should be obtained for all materials, not only because prices can fluctuate predictably but also because the haulage rates to various sites could be different, depending on their distance from the supplier; and the size of loads can dramatically affect the transport costs. The quantity required for each unit of work must be considered for each material.The following breakdown was used for material rate calculation. 1. Asphalt Concrete a. Wearing and Binding Course i. Bitumen ii. 01 Aggregate b. Prime Coat i. Bitumen for MC 30 ii. Naphthalene c. Tack Coat i. Bitumen for RC 70 ii. Kerosene 2. Cement Concrete a. Cement b. Crushed Sand c. 01 Aggregate d. 02 Aggregate e. Admixture f. Curing Chemical 162 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
5.9.3 Equipment Rates [16] The following breakdown was used for equipment rate calculation. 1. Asphalt Concrete a. Wearing and Binding Course i. Paver ii. Roller b. Prime Coat i. Bitumen Distributor c. Tack Coat i. Bitumen Distributor 2. Cement Concrete a. Mixer b. Vibrator c. Other tools
5.10 Economic Analysis As per the general comparison carried under Section 1.1, there are several points that favor rigid pavements over their flexible pavement counterparts. But, to be specific to this research’s area of concern, the design values of the two pavement structure alternatives carried under the previous sections shall be compared for their respective advantages and drawbacks. To arrive at the overall intended purpose of this research, economical comparisons shall be considered the primary procedure. Again as per Section 2.4, not only their initial investments are the sole consideration, but items like: Vehicle user operation costs (Rolling Resistance and Fuel Consumption) Early Completion, Future maintenance costs, etc.
5.10.1 Rigid Pavement 5.10.1.1 Initial Investment i. Values As it can be referred from the Cost Break down, Take off and Bill of Quantity attached in Appendix F, for one case (that is: for a design year and soil subgrade CBR) the total construction cost can be computed. And these costs are based on the design based on AASHTO (1993) of two-way, two-lane rural road way. It only consists of the pavement structure layers above the subbase. Tables 5.1 to 5.5 contain the initial investment costs in Birr in the years 2014 and 2015 per km.
163 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.85: Initial Investment costs of Rigid Pavements for 2014 and 2017 Subgrade CBR 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
175 msa, Subbase of 150 mm 2014 2017 17939581.81 22977447.93 17725993.81 22703879.29 17725993.81 22703879.29 17725993.81 22703879.29 17725993.81 22703879.29 17725993.81 22703879.29 17512405.81 22430310.64 17512405.81 22430310.64 17512405.81 22430310.64 17512405.81 22430310.64 17512405.81 22430310.64 17512405.81 22430310.64 17298817.81 22156741.99 17298817.81 22156741.99 17298817.81 22156741.99 17298817.81 22156741.99 17298817.81 22156741.99 17298817.81 22156741.99 17298817.81 22156741.99 17298817.81 22156741.99 17298817.81 22156741.99 17085229.81 21883173.34 17085229.81 21883173.34 17085229.81 21883173.34
198 msa, Subbase of 150 mm 2014 2017 18153169.81 23251016.58 18153169.81 23251016.58 17939581.81 22977447.93 17939581.81 22977447.93 17939581.81 22977447.93 17939581.81 22977447.93 17939581.81 22977447.93 17939581.81 22977447.93 17725993.81 22703879.29 17725993.81 22703879.29 17725993.81 22703879.29 17725993.81 22703879.29 17725993.81 22703879.29 17725993.81 22703879.29 17725993.81 22703879.29 17725993.81 22703879.29 17512405.81 22430310.64 17512405.81 22430310.64 17512405.81 22430310.64 17512405.81 22430310.64 17512405.81 22430310.64 17512405.81 22430310.64 17512405.81 22430310.64 17298817.81 22156741.99
Table 5.86: Initial Investment costs of Rigid Pavements for 2014 and 2017 Subgrade CBR 2 3 4 5 6 7 8 9 10
251 msa, Subbase of 150 mm 2014 2017 18793933.81 24071722.53 18580345.81 23798153.88 18580345.81 23798153.88 18580345.81 23798153.88 18580345.81 23798153.88 18580345.81 23798153.88 18366757.81 23524585.23 18366757.81 23524585.23 18366757.81 23524585.23
310 msa, Subbase of 150 mm 2014 2017 19275045.94 24687942.52 19275045.94 24687942.52 19275045.94 24687942.52 19061457.94 24414373.87 19061457.94 24414373.87 19061457.94 24414373.87 19061457.94 24414373.87 19061457.94 24414373.87 18847869.94 24140805.23 164
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
18366757.81 18366757.81 18366757.81 18366757.81 18153169.81 18153169.81 18153169.81 18153169.81 18153169.81 18153169.81 18153169.81 18153169.81 17939581.81 17939581.81 17939581.81
23524585.23 23524585.23 23524585.23 23524585.23 23251016.58 23251016.58 23251016.58 23251016.58 23251016.58 23251016.58 23251016.58 23251016.58 22977447.93 22977447.93 22977447.93
AAiT, SCEE
18847869.94 18847869.94 18847869.94 18847869.94 18847869.94 18847869.94 18634281.94 18634281.94 18634281.94 18634281.94 18634281.94 18634281.94 18634281.94 18634281.94 18634281.94
24140805.23 24140805.23 24140805.23 24140805.23 24140805.23 24140805.23 23867236.58 23867236.58 23867236.58 23867236.58 23867236.58 23867236.58 23867236.58 23867236.58 23867236.58
Table 5.87: Initial Investment costs of Rigid Pavements for 2014 and 2017 Subgrade CBR 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 20 22 25 30 31 32 35 86
374 msa, Subbase of 150 mm 2014 2017 19702221.94 25235079.82 19702221.94 25235079.82 19702221.94 25235079.82 19702221.94 25235079.82 19702221.94 25235079.82 19488633.94 24961511.17 19488633.94 24961511.17 19488633.94 24961511.17 19488633.94 24961511.17 19488633.94 24961511.17 19488633.94 24961511.17 19275045.94 24687942.52 19275045.94 24687942.52 19275045.94 24687942.52 19275045.94 24687942.52 19275045.94 24687942.52 19275045.94 24687942.52 19275045.94 24687942.52 19275045.94 24687942.52 19275045.94 24687942.52 19061457.94 24414373.87 19061457.94 24414373.87 19061457.94 24414373.87
175 msa, Subbase of 400 mm 2014 2017 18425669 23600040 18212081 23326471 18212081 23326471 17998493 23052903 17998493 23052903 17998493 23052903 17998493 23052903 17998493 23052903 17784905 22779334 17784905 22779334 17784905 22779334 17784905 22779334 17784905 22779334 17571317 22505765 17571317 22505765 17571317 22505765 17571317 22505765 17357729 22232197 17357729 22232197 17357729 22232197 17144141 21958628 16930553 21685059 16930553 21685059 165
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
90
19061457.94
24414373.87
AAiT, SCEE
16930553
21685059
Table 5.88: Initial Investment costs of Rigid Pavements for 2014 and 2017 Subgrade CBR 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
198 msa, Subbase of 400 mm 2014 2017 18639257 23873609 18639257 23873609 18425669 23600040 18425669 23600040 18212081 23326471 18212081 23326471 18212081 23326471 18212081 23326471 17998493 23052903 17998493 23052903 17998493 23052903 17998493 23052903 17998493 23052903 17998493 23052903 17784905 22779334 17784905 22779334 17784905 22779334 17784905 22779334 17571317 22505765 17571317 22505765 17357729 22232197 17357729 22232197 17144141 21958628 16930553 21685059
251 msa, Subbase of 400 mm 2014 2017 19280021 24694314 19066433 24420746 19066433 24420746 18852845 24147177 18852845 24147177 18852845 24147177 18852845 24147177 18852845 24147177 18639257 23873609 18639257 23873609 18639257 23873609 18639257 23873609 18639257 23873609 18639257 23873609 18425669 23600040 18425669 23600040 18425669 23600040 18212081 23326471 18212081 23326471 18212081 23326471 17998493 23052903 17784905 22779334 17571317 22505765 17571317 22505765
Table 5.89: Initial Investment costs of Rigid Pavements for 2014 and 2017 Subgrade CBR 2 3 4 5 6 7 8 9
310 msa, Subbase of 400 mm 2014 2017 19761133 25310534 19761133 25310534 19547545 25036966 19547545 25036966 19547545 25036966 19333957 24763397 19333957 24763397 19333957 24763397
374 msa, Subbase of 400 mm 2014 2017 20188309 25857672 20188309 25857672 20188309 25857672 19974721 25584103 19974721 25584103 19974721 25584103 19761133 25310534 19761133 25310534 166
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
10 11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
19333957 19120369 19120369 19120369 19120369 19120369 19120369 19120369 18906781 18906781 18906781 18906781 18479605 18479605 18266017 18052429
24763397 24489828 24489828 24489828 24489828 24489828 24489828 24489828 24216260 24216260 24216260 24216260 23669123 23669123 23395554 23121985
AAiT, SCEE
19761133 19761133 19761133 19761133 19547545 19547545 19547545 19547545 19547545 19333957 19333957 19333957 19120369 18906781 18693193 18693193
25310534 25310534 25310534 25310534 25036966 25036966 25036966 25036966 25036966 24763397 24763397 24763397 24489828 24216260 23942691 23942691
167 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
20600000
19600000
Cost per km in Birr
175 msa, 150 mm 198 msa, 150 mm 251 msa, 150 mm
310 msa, 150 mm
18600000
374 msa, 150 mm 175 msa, 400 mm 198 msa, 400 mm 251 msa, 400 mm 17600000
310 msa, 400 mm 374 msa, 400 mm
16600000 0
5
10
15
20
25
30
35
40 45 50 55 60 Subgrade CBR, %
65
70
75
80
85
90
95 100
Figure 5.17: Initial Investment costs of Rigid Pavements for 2014 in Birr/km 168 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
26000000
25000000
Cost per km in Birr
175 msa, 150 mm 198 msa, 150 mm
24000000
251 msa, 150 mm 310 msa, 150 mm 374 msa, 150 mm 175 msa, 400 mm
23000000
198 msa, 400 mm 251 msa, 400 mm 310 msa, 400 mm 22000000
374 msa, 400 mm
21000000 0
5
10
15
20
25
30
35
40 45 50 55 60 Subgrade CBR, %
65
70
75
80
85
90
95 100
Figure 5.18: Initial Investment costs of Rigid Pavements for 2017 in Birr/km 169 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
ii. Significance As we can see from the tables (Tables 5.1 to 5.5), the initial investment for the years 2014 (Current construction cost breakdown) and 2017 (year of construction beginning) was presented. And the future value on 2017 was forecasted by an inflation rate of 8.16 % from the present value (2014) by FW 2017 = FW 2014 (1 + 0.0816) 3. That is: in order to predict what the cost of materials and construction equipments will be, one needs to know the rate at which a country grows. One of the parameters used in predicting these prices is the forecasted inflation rate of the country. Thus, in order to estimate the price indices, one needs to know the forecasted inflation rate. In economics, inflation is a sustained increase in the prices of commodities in an economy over a period of time and is influenced by the availability of materials in addition to other parameters, and reflects the purchasing power of money. The inflation rate of a country can be qualitatively predicted by observing past trends or quantitatively forecasted by implementing analytical models such as regression and Naïve Bayes based forecasts. Tables 5.90 and 5.91: Past and forecasted inflation values of Ethiopia (Source: www.tradingeconomics.com (the last two values were obtained by training a neural network (naïve bayes’ algorithm)) [18] Year 2014 2013 2012 2011 2010 2009 2008 2007 2006 2005 2004 2003 2002 2001
Jan 7.8 12.5 32 17.7 7.6 37.8 19.7 16.6 9.6 9 3.1 -12.3 -6.9 -2.8
Feb 7.9 10.9 36.3 16.5 7 32.9 22.9 17.5 10.3 8.72 2.92 14.4 -7.3 -3.8
Mar 8.8 7.6 32.5 25 7.4 23.7 29.6 18.6 9.7 8.1 2.9 15.9 4.7 -8.1
Apr 9.1 6.1 29.8 29.5 6.8 23.4 29.7 20 8.3 7.86 4.12 17.39 -4.1 -11.4 Year 2015 2020 2030 2040 2050
May Jun
Jul Aug Sept Oct Nov Dec Average 8.4 6.3 7.4 8 7 6.9 8.5 7.9 7.7 8.06 25.5 20.5 20 20.2 18.9 15.8 15.6 12.9 23.33 34.7 38.1 39.2 40.6 40.1 39.8 39.2 35.9 33.025 7.4 7.3 5.7 5.3 7.5 10.6 10.2 14.5 8.108 14.1 2.7 -3.7 -3.9 -4.1 -3.7 0.6 7.1 10.575 39.1 55.2 64.1 61.7 59.6 55.4 49.4 39.3 43.808 16 15.1 14.3 16 17.7 18.7 18.1 18.4 17.25 12.2 10.8 12.6 13.5 12.8 14.5 15.3 17.2 12.23 7.98 10.7 11.6 11.5 12.1 10.2 10.6 10.2 9.88 3.99 2.38 1.53 1.16 2.21 3.69 5.33 6.65 3.33 17.45 17.77 17.19 17.49 13.04 11.78 8.58 5.51 12.016 -3.4 -1.2 2.28 5.77 5.63 6.79 6.81 9.73 1.5675 -10.6 -10.7 -31.6 31.1 -7.5 -5.7 -3.4 -3.4 -5.658 Forecasted IR (%) 8.16 5.15 4.14 0.67 -2.27 170
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
As we can see from Figures 5.1 and 5.2, the 400 mm thick subbase constituted rigid pavement structures bears smaller construction cost than its 150 mm counterpart for any design period for subgrade CBRs less than 30 %. 5.10.1.2 Maintenance and Rehabilitation Costs Even though rigid pavements are well known for their minimum rehabilitation and maintenance costs, they shall rather be considered for the economic comparison to be satisfactory. Since rigid pavements have not been constructed as road way pavement in Ethiopia, there is no as such articulated data on maintenance and rehabilitation costs. Therefore, the researchers faced problem to picture what value there will be at a time and in the long run. This necessitated, review of literatures once again. Doing so, Nebraska Department of Roads, Pavement Maintenance Manual (2002) was used for guidance. The following table (Table 5.8) contains guide for rigid pavements’ maintenance that shall be considered. Table 5.92: Maintenance and Rehabilitation Methods that shall be considered for Rigid Pavements and their Expected Life [19] Treatment Expected Life Crack & Joint Seal/Fill 4-7 Partial/Full Depth Slab/Joint Repair 10 - 15 Thin Hot Mix Overlay (1.5 ”) 6 - 10 Mud jacking 10 - 15 Diamond Grinding 12 - 15 Cross Stitching 10 - 15 Slab Replacement 20 + Thick Hot Mix Overlay 8 - 12 And of the above listed, this research will consider Crack & Joint Seal/Fill (5 years expected life and cost of 10.056 Birr/ml of joint in 2014), Partial/Full Depth Slab/Joint Repair (13 years expected life and cost of 120.48 Birr/m2 in 2014) and Other Miscellaneous Treatments Unforeseen Presently (13 years expected life and cost of 170.965 Birr/m2 in 2014). All other detail works is shown in Appendix F
171 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.93: Maintenance Costs of the Rigid Pavement at Different Intervals Until 2057 (40 years design Period (as of 2017)
Year
Inflation percent
2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049
8.16 8.16 8.16 8.16 8.16 8.16 5.15 5.15 5.15 5.15 5.15 5.15 5.15 5.15 5.15 5.15 4.14 4.14 4.14 4.14 4.14 4.14 4.14 4.14 4.14 4.14 0.67 0.67 0.67 0.67 0.67 0.67 0.67 0.67 0.67 0.67
Crack and Joint Partial/Full Depth Miscellaneous Seal/Fill Slab/Joint Repair (Grinding etc) Expenditures in Interval per Unit Measurement ------------------------17.30694566 --------------22.24676234 ---------318.2167 449.3931292 ---27.78037407 --------------34.02717981 --------------37.64968167 ---528.1924191 748.2725937 ---------38.92796056 --------172
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
2050 -2.27 2051 -2.27 2052 -2.27 2053 -2.27 2054 -2.27 2055 -2.27 2056 -2.27 2057 -2.27 Total Unit Costs in Birr Total Cost in Birr (40 Years)
--36.82523145 -----214.7641356 713016.9301
AAiT, SCEE
--------845.4110985 6763288.788
--------1197.665723 9581325.783
Table 5.94: Total Maintenance and Rehabilitation Costs at 20, 25, 30, 35 and 40 Years of Design Periods (in Birr) Crack and Joint Partial/Full Depth Miscellaneous Seal/Fill* Slab/Joint Repair** (Grinding etc)** 2036 20 223549.2 2537749 3595145 2041 25 336519.4 2537749 3595145 2046 30 461516.3 6763289 9581326 2051 35 590757.2 6763289 9581326 2057 40 713016.9 6763289 9581326 *(Considering 3 lines (2 edge & center) longitudinally (3*1000 = 3000 m) and 40 transverse joints per 1 km (40*8 = 320 m) Total of 3320 m Year Design Period
** 8 m width carriage way and 1 km length, therefore, 8*1000 = 8000 m2
173 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
20000000 18000000 16000000
Cost in Birr
14000000 Crack and Joint Seal/Fill Partial/Full Depth Slab/Joint Repair Miscellaneous
12000000
10000000 8000000 6000000 4000000
Total Maintenance Cost
2000000 0 20
22
24
26
28 30 32 34 Design Period, Years
36
38
40
Figure 5.19: Maintenance Costs (as of 2017) of the Rigid Pavement in different Design Periods 5.10.1.3 Total Cost (Initial + Maintenance) The combined cost of construction and maintenance is shown here under. Table 5.95 to 5.99: Total Cost (Construction + Maintenance) of Rigid Pavements for different design periods Subgrade CBR 2 3 4 5 6 7 8 9 10 11 12 13 14 15
175 msa, Subbase of 150 mm Maintenance Construction 3595145 22977447.93 3595145 22703879.29 3595145 22703879.29 3595145 22703879.29 3595145 22703879.29 3595145 22703879.29 3595145 22430310.64 3595145 22430310.64 3595145 22430310.64 3595145 22430310.64 3595145 22430310.64 3595145 22430310.64 3595145 22156741.99 3595145 22156741.99
Total 26572593 26299024 26299024 26299024 26299024 26299024 26025456 26025456 26025456 26025456 26025456 26025456 25751887 25751887
198 msa, Subbase of 150 mm Maintenance Construction 3595145 23251016.58 3595145 23251016.58 3595145 22977447.93 3595145 22977447.93 3595145 22977447.93 3595145 22977447.93 3595145 22977447.93 3595145 22977447.93 3595145 22703879.29 3595145 22703879.29 3595145 22703879.29 3595145 22703879.29 3595145 22703879.29 3595145 22703879.29
Total 26846162 26846162 26572593 26572593 26572593 26572593 26572593 26572593 26299024 26299024 26299024 26299024 26299024 26299024 174
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
3595145 3595145 3595145 3595145 3595145 3595145 3595145 3595145 3595145 3595145
16 20 22 25 30 31 32 35 86 90
22156741.99 22156741.99 22156741.99 22156741.99 22156741.99 22156741.99 22156741.99 21883173.34 21883173.34 21883173.34
Subgrade CBR 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
251 msa, Subbase of 150 mm Maintenance Construction 9581326 24071722.53 9581326 23798153.88 9581326 23798153.88 9581326 23798153.88 9581326 23798153.88 9581326 23798153.88 9581326 23524585.23 9581326 23524585.23 9581326 23524585.23 9581326 23524585.23 9581326 23524585.23 9581326 23524585.23 9581326 23524585.23 9581326 23251016.58 9581326 23251016.58 9581326 23251016.58 9581326 23251016.58 9581326 23251016.58 9581326 23251016.58 9581326 23251016.58 9581326 23251016.58 9581326 22977447.93 9581326 22977447.93 9581326 22977447.93
Subgrade CBR 2 3
25751887 25751887 25751887 25751887 25751887 25751887 25751887 25478318 25478318 25478318
AAiT, SCEE
3595145 3595145 3595145 3595145 3595145 3595145 3595145 3595145 3595145 3595145
22703879.29 22703879.29 22430310.64 22430310.64 22430310.64 22430310.64 22430310.64 22430310.64 22430310.64 22156741.99
26299024 26299024 26025456 26025456 26025456 26025456 26025456 26025456 26025456 25751887
Total 33653048.53 33379479.88 33379479.88 33379479.88 33379479.88 33379479.88 33105911.23 33105911.23 33105911.23 33105911.23 33105911.23 33105911.23 33105911.23 32832342.58 32832342.58 32832342.58 32832342.58 32832342.58 32832342.58 32832342.58 32832342.58 32558773.93 32558773.93 32558773.93
310 msa, Subbase of 150 mm Maintenance Construction 9581326 24687942.52 9581326 24687942.52 9581326 24687942.52 9581326 24414373.87 9581326 24414373.87 9581326 24414373.87 9581326 24414373.87 9581326 24414373.87 9581326 24140805.23 9581326 24140805.23 9581326 24140805.23 9581326 24140805.23 9581326 24140805.23 9581326 24140805.23 9581326 24140805.23 9581326 23867236.58 9581326 23867236.58 9581326 23867236.58 9581326 23867236.58 9581326 23867236.58 9581326 23867236.58 9581326 23867236.58 9581326 23867236.58 9581326 23867236.58
Total 34269268.52 34269268.52 34269268.52 33995699.87 33995699.87 33995699.87 33995699.87 33995699.87 33722131.23 33722131.23 33722131.23 33722131.23 33722131.23 33722131.23 33722131.23 33448562.58 33448562.58 33448562.58 33448562.58 33448562.58 33448562.58 33448562.58 33448562.58 33448562.58
374 msa, Subbase of 150 mm Total Maintenance Construction 9581326 25235079.82 34816405.82 9581326 25235079.82 34816405.82
175 msa, Subbase of 400 mm Maintenance Construction 3595145 23600040 3595145 23326471
Total 27195185 26921616 175
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
4 5 6 7 8 9 10 11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
Subgrade CBR 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 20 22 25
9581326 9581326 9581326 9581326 9581326 9581326 9581326 9581326 9581326 9581326 9581326 9581326 9581326 9581326 9581326 9581326 9581326 9581326 9581326 9581326 9581326 9581326
25235079.82 25235079.82 25235079.82 24961511.17 24961511.17 24961511.17 24961511.17 24961511.17 24961511.17 24687942.52 24687942.52 24687942.52 24687942.52 24687942.52 24687942.52 24687942.52 24687942.52 24687942.52 24414373.87 24414373.87 24414373.87 24414373.87
198 msa, Subbase of 400 mm Maintenance Construction 3595145 23873609 3595145 23873609 3595145 23600040 3595145 23600040 3595145 23326471 3595145 23326471 3595145 23326471 3595145 23326471 3595145 23052903 3595145 23052903 3595145 23052903 3595145 23052903 3595145 23052903 3595145 23052903 3595145 22779334 3595145 22779334 3595145 22779334 3595145 22779334
34816405.82 34816405.82 34816405.82 34542837.17 34542837.17 34542837.17 34542837.17 34542837.17 34542837.17 34269268.52 34269268.52 34269268.52 34269268.52 34269268.52 34269268.52 34269268.52 34269268.52 34269268.52 33995699.87 33995699.87 33995699.87 33995699.87
Total 27468754 27468754 27195185 27195185 26921616 26921616 26921616 26921616 26648048 26648048 26648048 26648048 26648048 26648048 26374479 26374479 26374479 26374479
AAiT, SCEE
3595145 3595145 3595145 3595145 3595145 3595145 3595145 3595145 3595145 3595145 3595145 3595145 3595145 3595145 3595145 3595145 3595145 3595145 3595145 3595145 3595145 3595145
23326471 23052903 23052903 23052903 23052903 23052903 22779334 22779334 22779334 22779334 22779334 22505765 22505765 22505765 22505765 22232197 22232197 22232197 21958628 21685059 21685059 21685059
251 msa, Subbase of 400 mm Maintenance Construction 9581326 24694314 9581326 24420746 9581326 24420746 9581326 24147177 9581326 24147177 9581326 24147177 9581326 24147177 9581326 24147177 9581326 23873609 9581326 23873609 9581326 23873609 9581326 23873609 9581326 23873609 9581326 23873609 9581326 23600040 9581326 23600040 9581326 23600040 9581326 23326471
26921616 26648048 26648048 26648048 26648048 26648048 26374479 26374479 26374479 26374479 26374479 26100910 26100910 26100910 26100910 25827342 25827342 25827342 25553773 25280204 25280204 25280204
Total 34275640 34002072 34002072 33728503 33728503 33728503 33728503 33728503 33454935 33454935 33454935 33454935 33454935 33454935 33181366 33181366 33181366 32907797 176
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
3595145 3595145 3595145 3595145 3595145 3595145
30 31 32 35 86 90
Subgrade CBR 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 20 22 25 30 31 32 35 86 90
22505765 22505765 22232197 22232197 21958628 21685059
310 msa, Subbase of 400 mm Maintenance Construction 9581326 25310534 9581326 25310534 9581326 25036966 9581326 25036966 9581326 25036966 9581326 24763397 9581326 24763397 9581326 24763397 9581326 24763397 9581326 24489828 9581326 24489828 9581326 24489828 9581326 24489828 9581326 24489828 9581326 24489828 9581326 24489828 9581326 24216260 9581326 24216260 9581326 24216260 9581326 24216260 9581326 23669123 9581326 23669123 9581326 23395554 9581326 23121985
26100910 26100910 25827342 25827342 25553773 25280204
Total 34891860 34891860 34618292 34618292 34618292 34344723 34344723 34344723 34344723 34071154 34071154 34071154 34071154 34071154 34071154 34071154 33797586 33797586 33797586 33797586 33250449 33250449 32976880 32703311
AAiT, SCEE
9581326 9581326 9581326 9581326 9581326 9581326
23326471 23326471 23052903 22779334 22505765 22505765
374 msa, Subbase of 400 mm Maintenance Construction 9581326 25857672 9581326 25857672 9581326 25857672 9581326 25584103 9581326 25584103 9581326 25584103 9581326 25310534 9581326 25310534 9581326 25310534 9581326 25310534 9581326 25310534 9581326 25310534 9581326 25036966 9581326 25036966 9581326 25036966 9581326 25036966 9581326 25036966 9581326 24763397 9581326 24763397 9581326 24763397 9581326 24489828 9581326 24216260 9581326 23942691 9581326 23942691
32907797 32907797 32634229 32360660 32087091 32087091
Total 35438998 35438998 35438998 35165429 35165429 35165429 34891860 34891860 34891860 34891860 34891860 34891860 34618292 34618292 34618292 34618292 34618292 34344723 34344723 34344723 34071154 33797586 33524017 33524017
177 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
36000000 35000000
34000000
Total Cost in Birr/km
33000000 175 msa, 150 mm
32000000
198 msa, 150 mm 251 msa, 150 mm
31000000
310 msa, 150 mm 374 msa, 150 mm
30000000
175 msa, 400 mm 198 msa, 400 mm
29000000
251 msa, 400 mm 310 msa, 400 mm
28000000
374 msa, 400 mm
27000000 26000000 25000000 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95100 Subgrade CBR, % Figure 5.20: Total Costs (as of 2017) of the Rigid Pavement in different Design Periods
5.10.2 Flexible Pavement 5.10.2.1 Initial Investment The analysis is made for 147 million equivalent standard axles (17 years design period). The values will be presented on a basis of future worth at 2017. Future worth method has been selected because using present worth value incorporates further uncertainties such as rate of return for 40 up coming years. This, combined with inflation rate (for purchasal of materials, machineries hiring and labor employment) leads to a seriously compromised result. Therefore, it is better to utilize only inflation rate and prepare a platform for comparison with rigid pavements on future worth basis. For the case of 178 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
initial investment (which has been computed in 2014), the future worth at 2017 is expressed as Initial Investment at 2014*((1+r)3), where r is equal to inflation rate expected between 2014 and 2017. Allowing 1m shoulder on both sides and taking 8m carriage way, the subbase and basecourse will extend 10 meters. The bituminous macadam and wearing asphalt course, however, will only be applied to the carriage way, i.e. 8m. Lastly, all computations will be strictly carried based on 1000m (1km) length basis. In order to draw better results, CBR values greater than 10% (not provided under the IRC Manual) have been considered. The trend in basecourse, subbase and macadam layer were observed as the subgrade CBR increases and the researchers have made their own reasonable thickness preference to design for subgrade class between 10% and 15%, 15% and 30%, and greater than 30%. Table 5.100: Trend in thickness variation as CBR value varies CBR (%)
Sub base Base course Bitumen Macadam AC (mm) (mm) (mm) (mm) 2 460 250 215 50 3 380 250 210 50 4 330 250 190 50 5 300 250 170 50 6 260 250 160 50 7 230 250 165 50 8 200 250 160 50 9 200 250 155 50 10 200 250 150 50 10 to 15 180 225 140 50 15 to 30 160 200 130 50 >30 150 110 50 Table 5.101: Initial Investment for different CBR values (see Appendix G I for details) CBR (%) 2 3 4 5 6 7 8 9 10 10-15 15-30 >30
Initial Investment (Birr at 2014) 15846312.00 15399416.00 14367481.00 13391520.00 12833572.00 12972611.00 12665650.00 12442650.00 12219650.00 11530101.00 10840552 9125610
Future Value (Birr at 2017) 20050639.95 19485173.94 18179446.96 16944544.94 16238562.73 16414491.42 16026087.83 15743921.69 15461755.54 14589256.08 13716756.62 11546807.89 179
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
CBR-vs-Initial Investment 18000000.00 16000000.00 14000000.00 12000000.00 10000000.00 8000000.00 CBR-vs-Initial Investment
6000000.00 4000000.00 2000000.00 0.00 0
5
10
15
20
25
30
35
Figure 5.21: CBR VS Initial Investment Graph (Investment at 2014) 5.10.2.2 Future Incurred Costs These include the cost of yearly overlay, periodic maintenance and major maintenance. The following table shows the values (at 2017) to be used for further computation. Note here that yearly overlay will be carried out starting from 2017 (first year of opening), periodic maintenance will be carried out every other 3 years (starting from 2020) and major maintenance will be carried out every other 5 years (starting from 2034). Table 5.102: Different Recurring Costs (Source: ERA, Procurement Division) Yearly overlay (Birr/km/year)
50,000
Periodic Maintenance (Birr/km/3 years)
2,500,000
Major maintenance (Birr/km/5 years)
11,000,000
5.10.2.3 Total Incurred Costs The following tables illustrate all incurred costs at different years in terms of future value with respect to 2017. See appendix G for details of how these values were acquired. Please note here that the term “Recurring Investment” represents the sum of yearly overlay, periodic maintenance and major maintenance. 180 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.103: Expenditure in Future Value with respect to 2017 at selected years (see Appendix G I & II for details) Expenditure in Future Value with respect to 2017 (Birr) CBR 2% Year Initial Investment Recurring investment Total 2017 20050639.95 50000 20100639.95 2037 20050639.95 62730731.13 82781371.07 2042 20050639.95 104472965.5 124523605.4 2047 20050639.95 156883742.1 176934382 2052 20050639.95 210682233.8 230732873.8 2057 20050639.95 252553049.4 272603689.3
Table 5.104: Expenditure in Future Value with respect to 2017 at selected years (see Appendix G I & II for details) Expenditure in Future Value with respect to 2017 (Birr) CBR 3% Year Initial Investment Recurring investment Total 2017 19485173.94 50000 19535173.94 2037 19485173.94 62730731.13 82215905.07 2042 19485173.94 104472965.5 123958139.4 2047 19485173.94 156883742.1 176368916 2052 19485173.94 210682233.8 230167407.8 2057 19485173.94 252553049.4 272038223.3
Table 5.105: Expenditure in Future Value with respect to 2017 at selected years (see Appendix G I & II for details) Expenditure in Future Value with respect to 2017 (Birr) CBR 4% Year Initial Investment Recurring investment Total 2017 18179446.96 50000 18229446.96 2037 18179446.96 62730731.13 80910178.09 2042 18179446.96 104472965.5 122652412.4 2047 18179446.96 156883742.1 175063189 2052 18179446.96 210682233.8 228861680.8 2057 18179446.96 252553049.4 270732496.3
181 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.106: Expenditure in Future Value with respect to 2017 at selected years (see Appendix G I & II for details)
Year 2017 2037 2042 2047 2052 2057
Expenditure in Future Value with respect to 2017 (Birr) CBR 5% Initial Investment Recurring investment Total 16944544.94 50000 16994544.94 16944544.94 62730731.13 79675276.07 16944544.94 104472965.5 121417510.4 16944544.94 156883742.1 173828287 16944544.94 210682233.8 227626778.8 16944544.94 252553049.4 269497594.3
Table 5.107: Expenditure in Future Value with respect to 2017 at selected years (see Appendix G I & II for details) Expenditure in Future Value with respect to 2017 (Birr) CBR 6% Year Initial Investment Recurring investment Total 2017 16238562.73 50000 16288562.73 2037 16238562.73 62730731.13 78969293.85 2042 16238562.73 104472965.5 120711528.2 2047 16238562.73 156883742.1 173122304.8 2052 16238562.73 210682233.8 226920796.5 2057 16238562.73 252553049.4 268791612.1
Table 5.108: Expenditure in Future Value with respect to 2017 at selected years (see Appendix G I & II for details)
Year 2017 2037 2042 2047 2052 2057
Expenditure in Future Value with respect to 2017 (Birr) CBR 7% Initial Investment Recurring investment Total 16414491.42 50000 16464491.42 16414491.42 62730731.13 79145222.55 16414491.42 104472965.5 120887456.9 16414491.42 156883742.1 173298233.5 16414491.42 210682233.8 227096725.2 16414491.42 252553049.4 268967540.8
182 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.109: Expenditure in Future Value with respect to 2017 at selected years (see Appendix G I & II for details) Expenditure in Future Value with respect to 2017 (Birr) CBR 8% Year Initial Investment Recurring investment Total 2017 16026087.83 50000 16076087.83 2037 16026087.83 62730731.13 78756818.95 2042 16026087.83 104472965.5 120499053.3 2047 16026087.83 156883742.1 172909829.9 2052 16026087.83 210682233.8 226708321.6 2057 16026087.83 252553049.4 268579137.2
Table 5.110: Expenditure in Future Value with respect to 2017 at selected years (see Appendix G I & II for details) Expenditure in Future Value with respect to 2017 (Birr) CBR 9% Year Initial Investment Recurring investment Total 2017 15743921.69 50000 15793921.69 2037 15743921.69 62730731.13 78474652.81 2042 15743921.69 104472965.5 120216887.2 2047 15743921.69 156883742.1 172627663.8 2052 15743921.69 210682233.8 226426155.5 2057 15743921.69 252553049.4 268296971.1
Table 5.111: Expenditure in Future Value with respect to 2017 at selected years (see Appendix G I & II for details)
Year 2017 2037 2042 2047 2052 2057
Expenditure in Future Value with respect to 2017 (Birr) CBR 10% Initial Investment Recurring investment Total 15461756 50000 15511755.54 15461756 62730731.13 78192486.67 15461756 104472965.5 119934721 15461756 156883742.1 172345497.6 15461756 210682233.8 226143989.4 15461756 252553049.4 268014804.9
183 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Table 5.112: Expenditure in Future Value with respect to 2017 at selected years (see Appendix G I & II for details) Expenditure in Future Value with respect to 2017 (Birr) CBR 10% - 15% Year Initial Investment Recurring investment Total 2017 14589256.08 50000 14639256.08 2037 14589256.08 62730731.13 77319987.21 2042 14589256.08 104472965.5 119062221.6 2047 14589256.08 156883742.1 171472998.1 2052 14589256.08 210682233.8 225271489.9 2057 14589256.08 252553049.4 267142305.5
Table 5.113: Expenditure in Future Value with respect to 2017 at selected years (see Appendix G I & II for details) Expenditure in Future Value with respect to 2017 (Birr) CBR 15% - 30% Year Initial Investment Recurring investment Total 2017 13716756.62 50000 13766756.62 2037 13716756.62 62730731.13 76447487.74 2042 13716756.62 104472965.5 118189722.1 2047 13716756.62 156883742.1 170600498.7 2052 13716756.62 210682233.8 224398990.4 2057 13716756.62 252553049.4 266269806
Table 5.114: Expenditure in Future Value with respect to 2017 at selected years (see Appendix G I & II for details)
Year 2017 2037 2042 2047 2052 2057
Expenditure in Future Value with respect to 2017 (Birr) CBR >30% Initial Investment Recurring investment Total 11546807.89 50000 11596807.89 11546807.89 62730731.13 74277539.02 11546807.89 104472965.5 116019773.4 11546807.89 156883742.1 168430550 11546807.89 210682233.8 222229041.7 11546807.89 252553049.4 264099857.3
184 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
5.10.3 Comparison between Flexible and Rigid Pavements The following series of graphs reveal the facts: 140000000 120000000 Linear (Rigid Pavement Initial Investment)
Cost in Birr/km
100000000 80000000 60000000
Linear (Rigid Pavement Total Cost)
40000000 20000000 0 0
20
40 60 Subgrade CBR, %
80
100
Figure 5.22: Comparison of Different Costs of the two Pavement Alternatives (as of 2017) for 20 years Design Period 140000000 Flexible Pavement Initial Investment
120000000
Cost in Birr/km
100000000
Rigid Pavement Initial Investment
80000000
Flexible Pavement Total Cost
60000000
40000000 Rigid Pavement Total Cost
20000000 0 0
20
40 60 Subgrade CBR, %
80
100 185
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Figure 5.23: Comparison of Different Costs of the two Pavement Alternatives (as of 2017) for 25 years Design Period 300000000 Flexible Pavement Initial Investment
250000000
Rigid Pavement Initial Investment
Cost in Birr/km
200000000 150000000
Flexible Pavement Total Cost
100000000
Rigid Pavement Total Cost
50000000 0 0
20
40 60 Subgrade CBR, %
80
100
Figure 5.24: Comparison of Different Costs of the two Pavement Alternatives (as of 2017) for 30 years Design Period 300000000 Flexible Pavement Initial Investment
250000000
Rigid Pavement Initial Investment
Cost in Birr/km
200000000
150000000 Flexible Pavement Total Cost
100000000
Rigid Pavement Total Cost
50000000
0 0
20
40 60 Subgrade CBR, %
80
100
186 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Figure 5.25: Comparison of Different Costs of the two Pavement Alternatives (as of 2017) for 35 years Design Period 300000000 Flexible Pavement Initial Investment
250000000
Rigid Pavement Initial Investment
Cost in Birr/km
200000000 150000000
Flexible Pavement Total Cost
100000000
Rigid Pavement Total Cost
50000000 0 0
20
40 60 Subgrade CBR, %
80
100
Figure 5.26: Comparison of Different Costs of the two Pavement Alternatives (as of 2017) for 40 years Design Period What do we entail from these results? 1. At 20 years design period, the initial investment for flexible pavements for any soil subgrade CBR is slightly less than that of its rigid pavement counterpart 2. But for the same design period (i.e. 20 years), adding the cost effects of routine maintenance (every 2 years), periodic overlay (every 1 year) and major rehabilitation (the first one after 17 years and then every 5 years after) to the total Life Cycle Cost of the flexible pavement, it exceeded with very much amount to its rigid pavement counterpart (which also included all of its related maintenance treatments) 3. For design period greater than 20 years, apparent from the rehabilitation cost, the initial investment of the flexible pavement alternative is higher than that of the rigid pavement alternative
187 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
References TO CHAPTER FIVE [1]
IRC, Indian Road Congress Manual (2001), Guidelines for the Design of Flexible Pavements – Second Edition, New Delhi, India
[2]
FHWA (2002), Life-Cycle Cost Analysis Primer, Department of Transportation Federal Highway Administration Washington, D.C., U.S.A.
[3]
ERA, Ethiopian Road Authority (2002), Pavement Design Manual – Volume II, Addis Ababa, Ethiopia (Pp. 14)
[4]
ERA, Ethiopian Road Authority (2002), Pavement Design Manual – Volume I, Addis Ababa, Ethiopia (Pp. 2-3, 2-7 to 2-8)
[5]
ERA, Ethiopian Road Authority (2002), Geometric Design Manual, Addis Ababa, Ethiopia (Pp. A-2)
[6]
ERA, Ethiopian Roads Authority (2011), Annual Traffic Count Report on the Federal Road Network in Ethiopia of 2009, Addis Ababa, Ethiopia (Pp. 9, 26 & 27)
[7]
ERA, Ethiopian Roads Authority (2009), Report on Annual Rural Traffic Movement in Ethiopia of 2008, Addis Ababa, Ethiopia (Pp. 14)
[8]
AACC & Sectoral Associations (2009), The Management of Commercial Road Transport in Ethiopia, Addis Ababa Chamber of Commerce – Private Sector Development Hub, Addis Ababa, Ethiopia(Pp. 19 – 21)
[9]
Core Consulting Engineers (2011), Detail Engineering Design for the Realignment of Beseka Crossing (Metehara Railway Crossing – Awash Junction) Road Project for Ethiopian Roads Authority (ERA), Addis Ababa, Ethiopia
[10] Roads Department, Botswana (2000), Guideline for Axle Load Surveys,ISBN 99912 - 0 - 358 – 3, Gaborone, Botswana (Pp. 26) [11] ERA, Ethiopian Roads Authority (2011), Feasibility of Rigid Pavements in Ethiopia – Trial 1 km Section Design at Metehara, Addis Ababa, Ethiopia
188 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
[12] Huang, Yang H. (2004), Pavement Analysis & Design, 2nd Edition - Pearson Education, Inc. – New Jersey, U.S.A. (Pp. 259 - 263) [13] AASHTO, American Association of State Highway & Transportation Officials (1993), Guide for the Design of Pavement Structures, Capitol Street – Washington D.C., U.S.A. (Part II) [14] Core Consulting Engineers (2011), Soil and Materials Report for the Re-alignment of Beseka Crossing (Metehara Railway Crossing – Awash Junction) Road Project for Ethiopian Roads Authority (ERA), Addis Ababa, Ethiopia [15] EBCS, Ethiopian Building Code of Standards (1995), Structural Use of Concrete, Ministry of Works & Urban Development (MoWUD), Addis Ababa, Ethiopia [16] Brook, Martin (2004), Estimating and Tendering for Construction Work-Third Edition, Elsevier Butterworth-Heinemann, Great Britain [17] http://www.constructionproxy.com/ [18] http://www.tradingeconomics.com; Based on Training a Neural Network Method by (Naïve Bayes’ algorithm) [19] NDoR, Nebraska Department of Roads (2002), Pavement Maintenance Manual, Nebraska, U.S.A. (Pp. 32)
189 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
CHAPTER SIX IMPLICATION IN ETHIOPIAN ROAD CONSTRUCTION 6.1 Introduction As a final and concluding part of this particular research entitled “The Design of the Roadway Section from Adama to Awash using Rigid Pavement and Its Implication in Ethiopian Road Construction”, the researchers have presented possible findings that are more or less related to the objectives set out at the very beginning. In doing so, Section 6.2 has been dedicated to the cost implication of using rigid pavements as an alternative to their flexible counterparts in Ethiopia (generally for different soil conditions and various design/performance periods). From there, it is possible to forward general comments. Apart from minimum cost implications, it is wise to assess factors related to construction ease and quality inspection in countries like Ethiopia with minimal exposure to the technology of rigid pavement construction. This will be widely discussed in Section 6.3. Finally, Section 6.4 covers Conclusions and Recommendations.
6.2 Economic Feasibility In this section, we shall consider three important economic criteria: Initial Investment, Life Cycle Cost and Total Cost of Construction and Operation.
6.2.1 Initial Investment Expenditure 6.2.1.1 High Volume Roads (the Case Study picked) As justified in Section 5.10 of the previous Chapter, for 20 years design period, the initial investment of flexible pavement alternatives is slightly less than their rigid counterpart (almost 19 % less; Eg. 20.5 million ETB and 25 million ETB). But for a design period exceeding 20 years, the use of rigid pavements is economical - even on the basis of initial investments.
190 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
6.2.1.2 Low Volume Roads This thesis has not assessed the case of low volume roads for rigid pavement design. But from the high volume road design and cost comparison done in the previous chapter, some comments can be made, i.e. initial investment of rigid pavements is likely to be higher than flexible pavements.
6.2.2 Life Cycle Cost Since flexible pavements incur larger future investments on maintenance and rehabilitation works (see Section 5.10 for types of maintenance and associated costs) than rigid pavements, under many circumstances, rigid pavements are less costly than flexible pavements.
6.2.3 Total Cost For high volume roads and low subgrade soil CBR, the Total Cost of Rigid Pavements (the sum of initial investment, maintenance and/or rehabilitation costs) on Life Cycle basis is definitely lower than the flexible pavement alternative.
6.3 Ease and Quality of Construction Though ease and quality have not been duly acknowledged in Ethiopian Road Construction scheme, they are dependent on the following: Competence level of design professionals, Experience of construction firms involved, Expertise in construction project management, Availability of equipments for construction and other activities, and Availability of skilled manpower
191 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
6.4 Conclusion and Recommendations The Road Sector Development Plan – Phase IV (RSDP IV) is currently being executed as part of the first phase of the Growth and Transformation Plan (GTP) of Ethiopia that was launched back in 2010. Despite having undeniably good prospects in nurturing the Road Network of Ethiopia, the RSDP IV has been and will continue to be criticized for one major setback: a staggering 60 to 75 percent of the total 125 billion ETB budget has been scheduled to be expended on upgrading, maintaining, rehabilitating and improving the existing road network. In order to highlight recommendations to improve the Ethiopian road network, this research made a case study on the highly trafficked corridor of the nation linking Adama with Awash. Having made numerous analyses on the relevant research data; the researchers have come to the conclusion that rigid pavements are indeed favorable for highly trafficked trunk roads. Had our nation been familiar with rigid pavement construction technology, such huge national budget could have been invested on further interconnection of the road network or perhaps some other infrastructure sector. Frankly speaking, rigid pavements are suitable for three general cases in the Ethiopian road construction scheme: 1. For High Volume roads; 2. For subgrade soils of low CBR (usually less than 10 %) and 3. For special rural roadways or urban highways of design periods greater than 20 years
192 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
APPENDIX A: PROGRAM DESCRIPTION AND ORGANIZATION A.1 Introduction The rigid pavement analysis program implemented here was used in this project as a means to analyze and design and check the rigid pavement design proposed in previous chapters. It was written wholly in a programming language called lisp. The need to build it arose from the fact that the design process’ cumbersomeness and its liability to hand-made errors. The first portions of this appendix highlight the operational characteristic of the software while the rest of this appendix shows how to write a basic version of the rigid pavement program and at the end, a complete common Lisp implementation has been provided as a means to interpret and correlate the algorithms provided in earlier sections. In this section of the appendix, we will discuss the basic components/modules/ used for making this algorithm and how they operate and communicate with each other. Peripheral programs used as utilities in this example (which have been marked as “PERIPHERAL”) are only highlighted and are not discussed in detail nor is the source code presented. Proprietary portions of the code (which have been marked as “PROPRIETARY”) are also not presented here, but are described at the theoretical level. There are five basic components used in the program: a rigid pavement analysis algorithm, a natural language semantic and linguistic analysis macro, a PDF output compiler macro, an artificially intelligent inference engine and “GLUE” utilities. The following subsections briefly describe each component in the order of their execution.
A.2 LISP: LISt Processing A.2.1 What is Lisp? Lisp is a programming language mainly used for artificial intelligence applications and database management systems. It was invented by John McCarthy at the Massachusetts Institute of Technology AI labs in 1959 and is the second oldest programming language preceded only by FORTRAN. Throughout the years several dialects and implementations have been made and used making it the largest subset of programming language dialects. Among these, AutoLISP(through which Autodesk’s AUTOCAD was implemented in), Emacs LISP(where Emacs is one of the most extensible code editors in use by programmers today) and Common LISP are the most popular dialects in use today.
193 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Lisp is different and perhaps very unique than other programming languages for many different reasons. The following section highlights how.
A.2.2 Comparison with other programming languages Lisp is very unique and has a completely different set of programming paradigms as compared to other mainstream languages such as java and C++. Some of these features include: Data structures: all Lisp source code is made up of nested or regular lists. This makes it easy for data manipulation and creation of abstraction to be readily available. This property also makes the code it generates maintainable and dynamic. Symbols are mainly the Homiconicity: homiconicity means the singularity of data with code i.e. code is data and data is code. This feature of lisp doesn’t exist in any other programming language in existence today making it the most powerful and extendable programming language. Homiconicity enables the programmer to manipulate code at runtime (i.e. the program that executes will be able to reprogram itself while running by inputting and outputting code instead of data throughout its execution), whereas in other programming languages, the program has to be modified manually before each execution occurs making their code static through execution. Homiconicity is the major reason as to why lisp is used in artificial intelligence applications. Macros: Macros in lisp have a completely different meaning than macros in other programming languages. In lisp, macros are used to generate and manipulate code at runtime making use of the code’s homiconicity. Macros are what make lisp a “programmable programming language” since it is possible to extend the language to one’s preference by constructing and combining new data structures and constructs. Macros also make it easy to implement another embedded programming language within lisp (like C++ or PROLOG). OOP (object oriented programming): Lisp (specifically Common Lisp) has a powerful object oriented programming system called the CLOS which enable it to interface with other languages such as C++ and Java.
A.2.3 Lisp and Artificial Intelligence Lisp was created in the late 50’s for the sole purpose of creating “thinking machines” and was exclusively used as an artificial intelligence system programming tool until the late 1980s after which it started to become a mainstream language because of the “AI winter” and lack of funding. Its areas of application included expert systems which are systems capable of performing reasoning as good as or better than a human within a certain domain, mathematical modules which were used for solving complex differential equations and residual integrals and more importantly, the development of intelligent database systems.
194 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
APPENDIX B: PROGRAM STRUCTURE B.1 Components In this appendix, we will discuss the basic components/modules/ used for making this algorithm and how they operate and communicate with each other. Peripheral programs used as utilities in this example (which have been marked as “PERIPHERAL”) are only highlighted and are not discussed in detail nor is the source code presented. Proprietary portions of the code (which have been marked as “PROPRIETARY”) are also not presented here, but are described at the theoretical level. The program is organized as a set of 3 basic components, namely input analysis and output, which in turn are broken down into smaller modules as shown below.
Preprocessing
Inference Engine
input
Natural Language Processing Mathematical Modules
Utilities
top-level
Unit Conversion
analysis
Rigid Pavement Analysis
PDF generator
output
Error Handlers
Preprocessing
Slab Thickness
Subgrade Reaction
Reinforcement
Formatted output
Figure B.1: Program Heirarchy
195 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
B.1.1 Input B.1.1.1 NLP: Natural Language Processing (PROPRIETARY) In order to make the software more user friendly, we have implemented a language processing engine which takes as input normal English questions such as “what is the value of the subgrade reaction?”, statements such as “the drainage condition of the area is excellent”, commands like “compute the thickness of slab required” and outputs a logically interpreted form of the input/query. However, the output is hauled to other parts of the software and is not seen on the display. The natural language processing engine is not available for the preliminary version of the program discussed here as it has some efficiency issues. B.1.1.2 PROLOG: PROgramming in LOGic (PROPRIETARY) Prolog is a programming language like Lisp and is the classic choice of language for writing AI or artificial intelligence applications. It uses a powerful inference engine to deduce new facts and statements from previously known rules and facts. Here in this software, it has been partially implemented as an embedded programming language for the purpose of interrelating concepts and storing relevant data in an orderly form. It generally takes logical queries or statements acquired from the NLP macro and either returns a valid response or stores the information as data for future reference. INPUT: enter numerical or import data.
INPUT PREPROCESSSING: classify the entered data into different categories or reject the input and display a warning message INPUT PARSING: nest useful information from the input and prepare the data for entry into the inference database. CLASSIFICATION: Further process the data and classify as either a command, a question, a formal query,a fact or numerical input. DATA ENTRY: If classified as a fact or numerical data, is reconstruct input as a formal data point and append into the inference database. DATA ENTRY: If input is classified as a question or a formal data query, reconstruct a formal query and evaluate the query, goto the analysis module if necessary and return output.
Figure B.2: Input processing and Data Storage
196 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
B.1.2 Analysis B.1.2.1 Rigid Pavement Analysis Core The main focus of discussion in the subsequent sections is the rigid pavement analysis and design algorithm which is responsible for retrieving relevant data from the PROLOG database, compute necessary parameters(such as details of the rigid pavement being designed) and store the newly acquired information back to the PROLOG database. Its operation is discussed in detail in the coming sections. B.1.2.2 “GLUE” Utilities (PERIPHERAL) By glue, one means interactive and in-process pieces of code that get executed at many levels/cycles throughout runtime. These pieces of code are crucial to the operation of this system that without them, many fatal errors would occur and the program would terminate. Included in this package are parsing functions, preprocessors, number crunchers, list manipulators, external libraries and indexing functions among several others.
DATA RETRIEVAL and CHECK: Retreive the necessary data and check the units used
UNIT CONVERSION: If a data point doesn't confirm with american standard units, it is converted into the ft-lb-sec system of units.
K-VALUE: Compute the effective subgrade reaction and store the value in the data-base
SLAB THICKNESS: Retrieve the effective subgrade reaction value and compute the slab thickness. Store the value in the database.
REINFORCEMENT: Calculate the reinforcement schedule and store in the database.
Figure B.3: Analysis and data access
197 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
B.1.3 OUTPUT B.1.3.1 The Output Module The output module is responsible for formally answering queries initiated by the user or other parts of the program. It is also in charge of generating data that is to be extracted by the report generator which is responsible for generating a formatted PDF output with all design parameters, describing all the necessary design information and details of the pavement project instantiated by the user. B.1.3.2 Report Generation Always the last module to be executed, the report generation function compiles all inputs, outputs and intermediate values to generate a standardized document with brief but full information regarding the rigid pave analyzed through the previous sections. This module utilizes an external library called cl-PDF (the source hosted at https://www.github.com/mbattyani/cl-pdf) which takes all the preprocessed data and generates a PDF document based on the user specifications. These include table and layout formats, fonts and other formatting options. The process for report generation takes two steps: preprocessing and PDF generation. By preprocessing, one means the preparation of the input and output metadata into actual strings of coherent information and the execution of other subroutines such as unit conversion, number trimming and number checking. The PDF generator takes this compiled form, attaches the proper specifications, generates the PDF file and saves it in the user-defined destination folder. The only input needed here would be this destination folder. QUERY ANSWERING: Compile user query and extract data from the database. If data is nonexistent, go back to the analysis module and compute necessary parameters. store these values into the database for future reference or display the relevant data.
PREPROCESSING: Format outputs it to a more readable form.
UNIT CONVERSION: If the user requests values in non-standardized units, covert units and store data.
DATA EXTRACTION: Check and choose which data to extract if there are too many solutions for a single query.
COMPILATION: Prepare data for use in report generation which includes parameter-value matching, organization and value unit matching.
REPORT GENERATION: Construct a PDF file with all necessary inputs, calculations equations, tables and design parameters for the analyzed input.(requires complete information
Figure B.4: Output
198 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
APPENDIX C: ALGORITHMS C.1 How to Read this Section The following sections present the inner workings of the program’s core analysis module and are accompanied by several pieces of pseudo-code which describe the level of abstraction of a certain component. These algorithms allow the reader to develop more insight as to how the program executes and how it handles error. Even though there are marked differences between these pseudo-codes and the actual source code, it is still possible to re-implement a similar version of this program from the algorithms. The actual source code presented in the coming appendices is the intended to be read along with these sections. Another significance for the algorithms presented here would be for the implementation of the program in another programming language like VB.net, Java or C++.
C.2 K-Value The effective subgrade reaction is computed by averaging out the subgrade soil properties with respect to the total relative damage calculated for seasonal variation of the roadbed mechanical properties. The top-level algorithm, which is shown in algorithm I.1 uses many child functions (Algorithms I.2 to I.6) to loop through the soil data for each month and compute relevant parameters such as relative damage and uncorrected k-values. Lines 1’ to 3 are used to collect input from either the user or from loaded data after which lines 4 to 7 execute algorithms I.2 to I.6 sequentially. Finally the k-value is either printed with an output function or is stored for use in other calculations. Algorithm C.2.1 k-value 1’ set months to a list/array containing January, February… 1 input slab-thickness, slab depth, loss of support, projected slab thickness 2 prompt or import For each month in months Input roadbed soil resilient modulus Input subbase elastic modulus 3 Assign property list For each month in months loop roadbed soil resilient modulus subbase elastic modulus 4 Do For each month in months loop Calculate Composite k-value (I.2) Calculate Modified k-value (I.3) Calculate relative damage (I.4) 5 compute average relative damage 6 for average relative damage get relative k-value (I.5) 199 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
7 Compute Effective k-value (I.6) 8 output Effective k-value As discussed in the previous chapters, many parameters are obtained using charts by pinpointing the intersection of projection lines emanating from the different portions of the graph. In this case however, implementing a machine vision application that will be used for the sole purpose of reading graphs would be quite cumbersome and inefficient. Therefore in order to accomplish this task, one needs to develop a module that reads values from an analytical representation of the graph, interpolates values for intermediate points, and maps normalized values to function calls. Hence, we have used three key concepts in developing the functions that do just this efficiently. These are regression models, linear mapping and normalization and are discussed briefly in the following few paragraphs. Analyzing each curve on the chart for the best-fit line by employing different types of regression models (logistic , exponential, logarithmic, linear, combined among others), one can reach a family of equations which can predict where a projection might fall accurately . Most of the fitted equations the algorithms use have a correlation coefficient ranging from 0.950 to 0.999. However, it should be noted that the accuracy of the estimations decline as the values applied to the functions increase in magnitude. Most of the charts that are used in the design process have families of curves which are labeled with a sequence of values. For example, the chart for evaluating the composite subgrade reaction has sequential values ranging from 100 to 1400 on the top-right part of the chart. Thus the values obtained from the regression equations need to be one of these sequential values (i.e. values from 100 to 1400 with an increment of 100 units). Otherwise, the value obtained is said to be not normalized. Normalization is a process of converting non-standard values into standard ones by the use of a multitude of techniques such as averaging, interpolating and integrating. In this case, normalization involves getting the interval in which the nonstandard value resides in and using the boundary points to interpolate the values location within a certain function. In most programming languages, data that needs to be stored is kept in structures known as arrays which are matrices of varying size and content depending on the type of information. In high-level languages such as Lisp, different types of data structures are provided among which hash-tables, lists and property lists are worth mentioning. Once such a structure is declared and data is stored in it, the programmer/user views or outputs data by calling a key or a marker to which a certain part of the data is attached to. In mathematics, this is called linear mapping. Most of the equations fitted are kept in these data constructs and are called whenever the previously computed value within the program equals one of the keys in the declared data constructs. 200 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Algorithm C.2.2 Composite k-value 1 Input roadbed soil resilient modulus(Rbsrm) Input subbase elastic modulus(Sbem) Input subbase thickness 2 Do for X= rbsrm If X is normalized then Set fx to: Do Get function for X Evaluate function at subbase thickness Else ` Normalize X Set fx to: Do Get function for floor X Evaluate function at subbase thickness of floor X (A) Get function for ceiling X Evaluate function at subbase thickness of ceiling X (B) Average A,B 3 Do for X= sbem If X is normalized then Set gx to: Do Get function for X Evaluate function at subbase thickness Else ` Normalize X Set gx to: Do Get function for floor X Evaluate function at subbase thickness of floor X(A) Get function for ceiling X Evaluate function at subbase thickness of ceiling X(B) Average A,B 4 Do composite k-value = hx Set hx to fx + gx If hx is normal then Get composite-k(hx) Else Interpolate for composite-k(X) Between: Composite-k(hx) of floor hx Composite-k(hx) of ceiling hx 5 Output Composite k-value Algorithm C.2.3 Modified k-value 1 Input Roadbed soil resilient modulus(rbsrm) Input composite k-value(comp-k) Input subgrade depth(sg) 2 Do for X= rbsrm 201 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
If X is normalized then Set hy to: Do Get function for X Evaluate function at subgrade depth Else ` Normalize X: Set hy to: Do Get function for floor X Evaluate function at subgrade depth of floor X (A) Get function for ceiling X Evaluate function at subgrade depth of ceiling X (B) Interpolate for X between A and B at subgrade depth 3 Do for X= comp-k Set modified k-value to: Get function for floor X Evaluate function at subgrade depth of floor X (A) Get function for ceiling X Evaluate function at subgrade depth of ceiling X (B) Interpolate for X between A and B at subgrade depth 4 Output modified k-value Algorithm C.2.4 Relative Damage 1 Input composite k-value (comp-k) Input projected slab thickness (PST) 2 Round projected slab thickness to integer. 3 Set relative damage to: Get function for PST Evaluate function at comp-k 4 Output relative damage In Algorithm I.5, we have implemented an analytical equation solver module which takes in an equation of one or several unknowns as input and if the unknown specified by the user can be isolated to one side of the equation, the module will return the isolated form of the equation. If the unknown cannot be separated, then the equation itself is returned. Once the equation has been solved for the unknown, the module will test whether the isolated form can be evaluated into a single number (i.e. tests if all the unknowns have bound values, or better yet if there are no unknowns) and if so, it will output the result. For the sake of clarity, the algorithm is shown here. Subroutine C.2.1 1 input equation 2 input unknown (usually a variable within the equation) 3 check whether equation contains variables. If not, terminate subroutine 4 check whether equation contains the unknown. If not, terminate subroutine 202 BSc. Thesis
AAiT, SCEE
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction 5 nest the equation (eg “x*3 + 4/x=tanx+3” becomes “((x +3) + (4/x)) = (tan(x) + 3)” 6 Do until left side equals the unknown for operation in (+ - * / exp log sin cos tan ...) Check the current operation Reverse the current operation and identify its operands If one of the operands is the unknown Do nothing Else use the reverse operation with one of the operands as the right side and the other one from the current side.
The solver module was used because one needs to reverse the process of looking up an equation and evaluating it for a certain value like we did in previous programs. Algorithm C.2.5 Relative k-value 1 Input projected slab thickness (PST) 2 Input relative damage 3 Set relative k-value to: Get function for PST Solve relative damage = Function (composite-k) for composite-k 4 Output relative k-value Algorithm C.2.6 Effective k-value 1 Input relative k-value (rel-k) 2 Input loss of support coefficient (ls) 3 round ls to integer 4. Set effective k-value to: Get function for ls Evaluate function at rel-k 5 Output effective k-value
C.3 Slab Thickness
(keys : ((Directional Distribution Factor, Dd ) (Lane distribution factor, Dl) (Growth factor, g) (Equivalent Single Axle Load , ESAL) (W18,W18) (Reliability , rel) (Standard Normal Deviate, std-nordev) (Permanent Serviceability Index, PSI) (Overall Standard Deviation, So) (Concrete Elastic Modulus, Ec) (Concrete Modulus of Rupture, Sc) (Drainage Coefficient, Cd) (Slab Thickness D) (Terminal Serviceability Index, TSL)) The slab thickness computation algorithm is a straight forward implementation of the equation provided for calculating slab thicknesses. Items to note would be i. Decomposition of the equation into 9 parts for convenience in code implementation, maintenance and overall efficiency of the program.
203 BSc. Thesis
AAiT, SCEE
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
ii. Fool-proofing programs involving logarithms to reject invalid values like zero and negative numbers preventing runtime errors. iii. The fact that there is no iteration for the computation of the slab thickness. Iteration procedures were avoided due to the presence of many pitfalls within equation and there is no way to guarantee the continuation of all the programs if one fails to deliver an output. An alternative here would be to take a suggestion from the user and give a table of outputs that compare the left-hand side of the equation with the right-hand side. A third alternative would be to accept a value from the user and print out the suitability of the value using a ranking system. In our case, the second alternative was the one implemented. Algorithm C.3.1 k1 1 Input w18 2 Set k1 to : (log W18) Algorithm C.3.2 k2 1 input std-nor-dev 2 Set k2 to : (std-nor-dev * so) Algorithm C.3.3 k3 1 input D 2 Set k3 to : (7.35 * (log D + 1)) Algorithm C.3.4 k4 1 Set k4 to :0.06 Algorithm C.3.5 k5 1 input PSI 2 Set k5 to :(log (PSI / (4.5-1.5))) Algorithm C.3.6 k6 1 input TSL 2 Set k6 to :(0.32 * TSL - 4.22) Algorithm C.3.7 k7 1 Input Sc, Cd, J-factor 2 Set k7 to :(log (Sc * Cd)/ (j-factor * 215.63)) Algorithm C.3.8 k8 1 Input D,Ec,K-value 2 Set k8 to :(log (D0.75 – 1.132) / (D0.75 – (Ec/kvalue)0.25) Algorithm C.3.9 k9 1 Input D 2 Set k9 to :((1.624*107/ (D +1)8.46)-1) Algorithm C.3.10 slab thickness 1 Set k10 to: Sum k1 to k9 204 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Algorithm C.3.11 slab thickness 1 Do until (k1 - slab thickness) < error-limit Compute slab-thickness Compute k1
C.4 Reinforcement The reinforcement schedule for the pavement is computed as a percentage of the total pavement cross-sectional area. The function takes steel working stress, friction factor and the length of the slab as input parameters and outputs the reinforcement schedule as percentage of the total area of the slab. Algorithm C.4.1 reinforcement 1. set reinforcement-percentage to ((f * l)/(2 * fs)) * 100) Once the percentage is computed, we can get the total reinforcement area of the slab, decide the type and size of bars used, development length and overall structural layout. The quantity should be the same for both longitudinal and transverse directions in the case of jointed reinforced rigid pavements. It should also be noted that the reinforcement area is calculated for a unit width of the slab (and hence the constant 12 in algorithm C.4.2 signifies the unit conversion from feet to inches). Algorithm C.4.2 reinforcement area 1. set reinforcement-area to (12 * slab-thickness * reinforcement-percentage) Other things to consider would be computing the steel working stress from yield strength of steel which is executed by the following algorithm. Algorithm C.4.3 steel yield strength to working stress 1. set working-stress to (0.75 * yield-strength)
C.5 Output Once all computations are done, the results are stored in variables by using the built-in “setf” function. For example, after the computation of a subgrade reaction a setf statement is initiated to store the final value from the executed function into an accessible variable. (setf k-value effective-k) Where effective-k is a meta-variable (an intermediate variable used for passing values to other variables) used to store the k-value. These final variables were set to pave an easy way for the output and report generation functions to take over. The output functions rearrange the values obtained from the previous procedures to a more complete and readable form 205 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
while the report generation functions initiate external libraries for the preparation of the PDF document. The output functions are also responsible for displaying requested or temporary information on the command screen. These information include warning messages, possible errors, help statements and intermediate values (values obtained at the end of a primary module execution such as the k-value and slab thickness modules). In the modified version of the program, the output functions also perform conversion of units, proper data storage for late requests and entry of final computed data into a database.
206 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
APPENDIX D: USER MANUAL This appendix is meant as a guide to the user of this program and illustrates basic features in the input and output of the program.
D.1 Data Input The data inputs in the preliminary and final version of the software are different. While the preliminary program (i.e. the one discussed here) only allows for numerical input, the final version of the program (still in development) can allow for imported data and natural language input in addition to numerical input. The final version has not been presented here for the sake of clarity in explaining these features. Thus, the user is only expected to follow directions printed on the command screen. Numerical values entered should also be in American units(ftpsi-pci) rather than in metric or imperial units.
D.1.1 K-value computation The program begins with the following prompt for the subbase thickness at which point the user is supposed to enter a value between 4 and 20 inches. subbase-thickness: Then follows depth to rigid foundation which accepts values between 2 and 10 feet. subgrade-depth:9 Loss of support assumes a value from 1 to 3 and converts decimal values into one of these whole numbers. loss of subbase support:2 The projected slab thickness should also be in between 6 and 14 inches. projected slab thickness:9 After this, the monthly values of the roadbed’s seasonal resilient modulus are entered and these should preferably be between 1000 and 20000 psi. MONTH : RBSRM JANUARY : 20000 FEBRUARY : 20000 MARCH : 10000 APRIL : 10000 MAY : 5000 JUNE : 5000 JULY : 5000 AUGUST : 20000 SEPTEMBER : 20000 OCTOBER : 20000 NOVEMBER : 15000 DECEMBER : 15000 The seasonal subbase resilient moduli follow and are to be values between 15000 and 1000000 psi. 207 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
MONTH : SBRM JANUARY : 30000 FEBRUARY : 40000 MARCH : 50000 APRIL : 30000 MAY : 40000 JUNE : 50000 JULY : 50000 AUGUST : 35000 SEPTEMBER : 40000 OCTOBER : 25000 NOVEMBER : 45000 DECEMBER : 50000 Once these data have been entered, the intermediate effective k-value is printed to show the user that there are no errors or warning messages present up to this point. 67.09655
D.1.2 Slab Thickness The slab thickness algorithm assumes a minimum of inputs and only requires the equivalent single axle load and the compressive strength of concrete as inputs. ESAL: 15000000 Compressive strength of concrete:40 The following “pseudo-table” will print out if the iteration for the slab thickness terminates successfully. log18 right-side delta 6.720159 ---- 5.642778 ---- 1.0773811 6.720159 ---- 6.0239196 ---- 0.6962395 6.720159 ---- 6.374411 ---- 0.34574795 6.720159 ---- 6.6996117 ---- 0.02054739 6.720159 ---- 6.9993734 ---- -0.27921438
D.1.3 Reinforcement The friction factor the steel’s working stress and the longitudinal length of the slab are provided as inputs here. friction factor: 1.5 steel working stress: 30000 length of slab: 36
D.2 Data Output In order to generate the final output as a PDF document, the program needs a file name or a destination folder as input which should be entered within brackets and quotations. file name: ("pave2.pdf") other examples include: (“c:/pave2.pdf”), (“c:/users/user/documents/pave2.pdf”). 208 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Once the destination file has been provided, the final values are printed out to show successful execution of the output module and the creation of the PDF document which can be found in the proposed destination folder. K-VALUE: 67.09655 pci SLAB THICKNESS: 10 in REINFORCEMENT PERCENTAGE: 0.089999996% REINFORCEMENT AREA PER UNIT WIDTH: 10.799999sq.in.
209 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
APPENDIX E: AN IMPLEMENTATION IN COMMON LISP E.1 K-Value ;All rights reserved © 2014 ELIAS YILMA. Licensed under the GPL. ;to-do ---> gracious exit from the program ;to-do ---> normalize-projected slab thickness (defpackage :k--final (:use :common-lisp ) (:export #:k-value #:ask-sb-thickness #:ask-sg-depth #:ask-sb-los #:ask-pst #:ask-sbrm #:ask-rbsrm #:composite-k #:prompt #:new-symbol #:comp-k-vs-fx+gx #:*months* #:avg-values #:interpolate-val #:normalizerbsrm #:normalize-sbrm #:modified-k #:normalize-comp-k #:interpolate #:relative-damage #:round-off-pst #:deepreplace #:solve-uf-eqn #:interpolate-sg-dep #:effective-k #:normalize-fx+gx #:interpolate-comp-k #:interpolate-modk #:normalize-sg-depth #:k-top)) (defun k-top() (prog () loop (k-value) (go loop))) ;k-value (defun k-value() "top-level: runs and evaluates variables and returns kvalue" ;get subbase thickness from the user:type nump ;(setf sb-thickness (prompt "subbase thickness:")) ;get subgrade depth from the user:type nump ;(setf sg-depth (prompt "subgrade depth:")) ;get loss of support value from the user ;(setf ls (prompt "loss of subbase support:")) ;get projected slab thickness(PST) from the user:type nump ;(setf pst (prompt "projected slab thickness:")) ;(round-off-pst) ;(format t "MONTH : RBSRM ~%") ;road-bed soil resilient modulus ;(loop for month in *months* do ;(setf (get 'rbsrm month) (prompt "~a : " month))) ;(format t "MONTH : SBRM ~%") ;subbase resilient/elastic modulus ;(loop for month in *months* do 210 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
; (setf (get 'sbrm month) (prompt "~a : " month))) ;(loop for month in *months* do (ask-sb-thickness) (ask-sg-depth) (ask-sb-los) (ask-pst) (format t "MONTH : RBSRM ~%") (loop for month in *months* do (ask-rbsrm month)) (format t "MONTH : SBRM ~%") (loop for month in *months* do (ask-sbrm month)) ;compute composite-k and modified k-values (loop for month in *months* do (let ((rbsrm (get 'rbsrm month)) (sbrm (get 'sbrm month))) (setf (get 'composite-k month) (composite-k rbsrm sbrm sb-thickness)) (setf (get 'modified-k month) (modified-k rbsrm composite-k sg-depth)) (setf (get 'rel-damage month) (relative-damage composite-k pst)))) ;average relative-damage value (setf sum-uf 0) (loop for month in *months* do (setf sum-uf (+ sum-uf (get 'rel-damage month)))) (setf avg-uf (/ sum-uf (length *months*))) ;effective-k corrected for relative-damage (setf rel-k-value (solve-uf-eqn pst avg-uf)) ;effective-k corrected fro loss of support (effective-k ls rel-k-value) (princ effective-k)) ;ask-sb-thickness ask-sg-depth ask-sb-los ask-pst (defun ask-sb-thickness() "prompt for subbase thickness while checking for whether the entered value is numerical" (setf val1 (prompt "~% sb-thickness:")) (cond ((numberp val1) (cond ((and (>= val1 4.0) (= val1 2) (= val1 0.0) (= val1 6) (= val1 15000) ( rbsrm '1000) (< rbsrm '2000)) (avg-values 'rbsrm sb-thickness '1000psi '2000psi) (if (and (> rbsrm '2000) (< rbsrm '3000)) (avg-values 'rbsrm sb-thickness'2000psi '3000psi) (if (and (> rbsrm '3000) (< rbsrm '5000)) (avg-values 'rbsrm sb-thickness'3000psi '5000psi) (if (and (> rbsrm '5000) (< rbsrm '7000)) (avg-values 'rbsrm sb-thickness '5000psi '7000psi) (if (and (> rbsrm '7000) (< rbsrm '10000)) (avg-values 'rbsrm sb-thickness '7000psi '10000psi) (if (and (> rbsrm '10000) (< rbsrm '12000)) (avg-values 'rbsrm sb-thickness '10000psi '12000psi) (if (and (> rbsrm '12000) (< rbsrm '16000)) (avg-values 'rbsrm sb-thickness '12000psi '16000psi) (if (and (> rbsrm '16000) (< rbsrm '20000)) (avg-values 'rbsrm sb-thickness '16000psi '20000psi) '1200)))))))))) (defun normalize-sbrm(sbrm sb-thickness) 214 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
"if standard values of sbrm are not met with, then the non-std value's gx value will be instantiated to the average of the top & bottom-most values the sbrm lies in" (if (< sbrm '15000) (eval (get '15000psi 'sbrm)) (if (and (> sbrm '15000) (< sbrm '30000)) (avg-values 'sbrm sb-thickness '15000psi '30000psi) (if (and (> sbrm '30000) (< sbrm '50000)) (avg-values 'sbrm sb-thickness'30000psi '50000psi) (if (and (> sbrm '50000) (< sbrm '75000)) (avg-values 'sbrm sb-thickness'50000psi '75000psi) (if (and (> sbrm '75000) (< sbrm '100000)) (avg-values 'sbrm sb-thickness '75000psi '100000psi) (if (and (> sbrm '100000) (< sbrm '200000)) (avg-values 'sbrm sb-thickness '100000psi '200000psi) (if (and (> sbrm '200000) (< sbrm '400000)) (avg-values 'sbrm sb-thickness '200000psi '400000psi) (if (and (> sbrm '400000) (< sbrm '600000)) (avg-values 'sbrm sb-thickness '400000psi '600000psi) (if (and (> sbrm '600000) (< sbrm '1000000)) (avg-values 'sbrm sb-thickness '600000psi '1000000psi) (eval (get '1000000psi 'sbrm)))))))))))) (setf (get '15000psi 'sbrm) '(- (* 49.21 (log sbthickness)) 43.19)) (setf (get '30000psi 'sbrm) '(- (* 52.73 (log sbthickness)) 43.2)) (setf (get '50000psi 'sbrm) '(- (* 55.36 (log sbthickness)) 47.03)) (setf (get '75000psi 'sbrm) '(- (* 56.61 (log sbthickness)) 46.01)) (setf (get '100000psi 'sbrm) '(- (* 56.51 (log sbthickness)) 44.37)) (setf (get '200000psi 'sbrm) '(- (* 60.69 (log sbthickness)) 48.09)) (setf (get '400000psi 'sbrm) '(- (* 63.01 (log sbthickness)) 47.81)) (setf (get '600000psi 'sbrm) '(- (* 65.11 (log sbthickness)) 48.99)) (setf (get '1000000psi 'sbrm) '(- (* 67.32 (log sbthickness)) 50.04)) (setf (get '1000psi 'rbsrm) '(* 102.509 (exp (* -0.126010 sb-thickness)))) (setf (get '2000psi 'rbsrm) '(* 104.33 (exp (* -0.0741556 sb-thickness)))) (setf (get '3000psi 'rbsrm) '(* 111.77 (exp (* -0.0609416 sb-thickness)))) (setf (get '5000psi 'rbsrm) '(* 127.83 (exp (* -0.0530787 sb-thickness)))) 215 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
(setf (get '7000psi 'rbsrm) '(* 137.65 (exp (* -0.0489196 sb-thickness)))) (setf (get '10000psi 'rbsrm) '(* 147.62 (exp (* -0.045285 sb-thickness)))) (setf (get '12000psi 'rbsrm) '(* 155.18 (exp (* -0.044319 sb-thickness)))) (setf (get '16000psi 'rbsrm) '(* 162.55 (exp (* -0.041954 sb-thickness)))) (setf (get '20000psi 'rbsrm) '(* 168.91 (exp (* -0.040163 sb-thickness)))) (defun modified-k(road-bed composite-k subgrade-depth) (let ((~sg-depth (new-symbol subgrade-depth 'ft)) (~composite-k (new-symbol composite-k 'pci))) (setf rbsrm (abs (- 20 (/ road-bed 1000)))) (setf hy (if (get ~sg-depth 'subgrade-depth) (eval (get ~sg-depth 'subgrade-depth)) (normalize-sg-depth sg-depth rbsrm))) (setf modified-k (if (get ~composite-k 'composite-k) (eval (get ~composite-k 'composite-k)) (normalize-comp-k composite-k hy))))) (defun normalize-comp-k(comp-k hy-val) (if (< comp-k 160) '50pci (if (and (> comp-k 50) (< comp-k 100)) (apply #'(lambda (val) (setf x1 50) (setf x2 100) (interpolate-mod-k 'composite-k val '50pci '100pci )) (list comp-k)) (if (and (> comp-k 100) (< comp-k 200)) (apply #'(lambda (val) (setf x1 100) (setf x2 200) (interpolate-mod-k 'composite-k val '100pci '200pci)) (list comp-k)) (if (and (> comp-k 200) (< comp-k 300)) (apply #'(lambda (val) (setf x1 200) (setf x2 300) (interpolate-mod-k 'composite-k val '200pci '300pci)) (list comp-k)) (if (and (> comp-k 300) (< comp-k 400)) (apply #'(lambda (val) (setf x1 300) (setf x2 400) (interpolate-mod-k 'composite-k val '300pci '400pci)) (list comp-k)) (if (and (> comp-k 400) (< comp-k 500)) (apply #'(lambda (val) (setf x1 400) (setf x2 500) (interpolate-mod-k 'composite-k val '400pci '500pci)) (list comp-k)) (if (and (> comp-k 500) (< comp-k 600)) (apply #'(lambda (val) (setf x1 500) (setf x2 600) (interpolate-mod-k 'composite-k val '500pci '600pci)) (list comp-k)) (if (and (> comp-k 600) (< comp-k 700)) (apply #'(lambda (val) (setf x1 600) (setf x2 700) 216 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
(interpolate-mod-k 'composite-k val '600pci '700pci)) (list comp-k)) (if (and (> comp-k 700) (< comp-k 800)) (apply #'(lambda (val) (setf x1 700) (setf x2 800) (interpolate-mod-k 'composite-k val '700pci '800pci)) (list comp-k)) (if (and (> comp-k 800) (< comp-k 1000)) (apply #'(lambda (val) (setf x1 800) (setf x2 1000) (interpolate-mod-k 'composite-k val '800pci '1000pci)) (list comp-k)) (if (and (> comp-k 1000) (< comp-k 1200)) (apply #'(lambda (val) (setf x1 1000) (setf x2 1200) (interpolate-mod-k 'composite-k val '1000pci '1200pci)) (list comp-k)) (if (and (> comp-k 1200) (< comp-k 1400)) (apply #'(lambda (val) (setf x1 1200) (setf x2 1400) (interpolate-mod-k 'composite-k val '1200pci '1400pci)) (list comp-k)) (eval (get '1400pci 'composite-k ))))))))))))))) (setf (get '10ft 'subgrade-depth) '(* 0.113 (expt rbsrm 1.879))) (setf (get '5ft 'subgrade-depth) '(* 4.178 (exp (* rbsrm 0.131)))) (setf (get '2ft 'subgrade-depth) '(* 9.795 (exp (* 0.109 rbsrm)))) (defun normalize-sg-depth(sg-depth rbsrm) (if (< sg-depth 2) 50 (if (and (> sg-depth 2) (< sg-depth 5)) (apply #'(lambda (val) (setf x1 2) (setf x2 5) (interpolate-sg-dep 'subgrade-depth val '2ft '5ft)) (list sg-depth)) (if (and (> sg-depth 5) (< sg-depth 10)) (apply #'(lambda (val) (setf x1 5) (setf x2 10) (interpolate-sg-dep 'subgrade-depth val '5ft '10ft)) (list sg-depth)) 60)))) (setf (setf (setf (setf (setf (setf (setf (setf (setf (setf (setf (setf
(get (get (get (get (get (get (get (get (get (get (get (get
'50pci 'composite-k) '(/ (+ hy 50) 2.4)) '100pci 'composite-k) '(/ (+ hy 33.68) 0.737)) '200pci 'composite-k) '(/ (+ hy 30) 0.275)) '300pci 'composite-k) '(/ (+ hy 29.65) 0.15)) '400pci 'composite-k) '(/ (+ hy 32.2) 0.107)) '500pci 'composite-k) '(/ (+ hy 32.2) 0.078)) '600pci 'composite-k) '(/ (+ hy 32) 0.061)) '700pci 'composite-k) '(/ (+ hy 30) 0.048)) '800pci 'composite-k) '(/ (+ hy 32) 0.041)) '1000pci 'composite-k) '(/ (+ hy 28) 0.0275)) '1200pci 'composite-k) '(/ (+ hy 34) 0.025)) '1400pci 'composite-k) '(/ (+ hy 33) 0.02)) 217
BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
(defun interpolate(x1 x2 y1 y2 x3) (let ((m (/ (- y2 y1) (- x2 x1))) (xf (- x3 x1))) (+ (* m xf) y1))) (defun relative-damage (composite-k PST) ;PST --> projected slab thickness (let ((~pst (new-symbol pst 'in))) (setf uf (eval (get ~pst 'pst))))) (setf (get 70.11)) (setf (get 114.6)) (setf (get 172.8)) (setf (get 245.7)) (setf (get 330.2)) (setf (get 540.7)) (setf (get 830.3))
'6in 'pst) '(+ (* -9.39 (log composite-k)) '7in 'pst) '(+ (* -14.7 (log composite-k)) '8in 'pst) '(+ (* -21.3 (log composite-k)) '9in 'pst) '(+ (* -29.2 (log composite-k)) '10in 'pst) '(+ (* -37.6 (log composite-k)) '12in 'pst) '(+ (* -57.1 (log composite-k)) '14in 'pst) '(+ (* -82.7 (log composite-k))
(defun round-off-pst() (cond ((< pst 6) (setf pst 6)) ((> pst 14) (setf pst 14)) (t (setf pst (round pst))))) (defun deep-replace(replacer replacee list1) (cond ((endp list1) nil) ((equal replacee (first list1)) (cons replacer (deepreplace replacer replacee (rest list1)))) ((atom (first list1)) (cons (first list1) (deep-replace replacer replacee (rest list1)))) (t (cons (deep-replace replacer replacee (first list1)) (deep-replace replacer replacee (rest list1)))))) (defun solve-uf-eqn(pst avg-uf) (let ((~pst (new-symbol pst 'in))) (compute (prefix->infix (deep-replace 'k 'composite-k (append (cons '= (list (get ~pst 'pst))) (list avg-uf)))) 'k))) (setf (get '0ls 'ls) '(expt 10 (- (* (log rel-k-value 10) 1.01) 0.010))) 218 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
(setf (get '1ls 'ls) '(expt 10 (- (* (log rel-k-value 10) 0.839) 0.067))) (setf (get '2ls 'ls) '(expt 10 (- (* (log rel-k-value 10) 0.640) 0.075))) (setf (get '3ls 'ls) '(expt 10 (- (* (log rel-k-value 10) 0.540) 0.178))) (defun effective-k(ls rel-k-value) (let ((~ls (new-symbol (values (round ls)) 'ls))) (setf effective-k (eval (get ~ls 'ls))))) (setf (setf (setf (setf (setf (setf (setf (setf (setf (setf (setf
(get (get (get (get (get (get (get (get (get (get (get
'80u '100u '125u '140u '150u '160u '165u '173u '180u '190u '200u
'comp-k) 'comp-k) 'comp-k) 'comp-k) 'comp-k) 'comp-k) 'comp-k) 'comp-k) 'comp-k) 'comp-k) 'comp-k)
50) 100) 200) 300) 400) 500) 600) 800) 1000) 1500) 2000)
(defun normalize-fx+gx(fx+gx) "if standard values of fx+gx are not met with, then the non-std value's fx value will be instantiated to the average of the top & bottom-most values the fx+gx lies in" (if (< fx+gx '80) (eval (get '80u 'comp-k)) (if (and (> fx+gx '80) (< fx+gx '100)) (apply #'(lambda (val) (setf x1 80) (setf x2 100) (interpolate-comp-k 'comp-k val '80u '100u)) (list fx+gx)) (if (and (> fx+gx '100) (< fx+gx '125)) (apply #'(lambda (val) (setf x1 100) (setf x2 125) (interpolate-comp-k 'comp-k val '100u '125u)) (list fx+gx)) (if (and (>= fx+gx '125) (< fx+gx '140)) (apply #'(lambda (val) (setf x1 125) (setf x2 140) (interpolate-comp-k 'comp-k val '125u '140u)) (list fx+gx)) (if (and (>= fx+gx '140) (< fx+gx '150)) (apply #'(lambda (val) (setf x1 140) (setf x2 150) 219 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
(interpolate-comp-k 'comp-k fx+gx))
val '140u
AAiT, SCEE
'150u)) (list
(if (and (>= fx+gx '150) (< fx+gx '160)) (apply #'(lambda (val) (setf x1 150) (setf x2 160) (interpolate-comp-k 'comp-k val '150u '160u)) (list fx+gx)) (if (and (>= fx+gx '160) (< fx+gx '165)) (apply #'(lambda (val) (setf x1 160) (setf x2 165) (interpolate-comp-k 'comp-k val '160u '165u)) (list fx+gx)) (if (and (>= fx+gx '165) (< fx+gx '173)) (apply #'(lambda (val) (setf x1 165) (setf x2 173) (interpolate-comp-k 'comp-k val '165u '173u)) (list fx+gx)) (if (and (>= fx+gx '173) (< fx+gx '180)) (apply #'(lambda (val) (setf x1 173) (setf x2 180) (interpolate-comp-k 'comp-k val '173u '180u)) (list fx+gx)) (if (and (>= fx+gx '180) (< fx+gx '190)) (apply #'(lambda (val) (setf x1 180) (setf x2 190) (interpolate-comp-k 'comp-k val '180u '190u)) (list fx+gx)) (if (and (>= fx+gx '190) (< fx+gx '200)) (apply #'(lambda (val) (setf x1 190) (setf x2 200) (interpolate-comp-k 'comp-k val '190u '200u)) (list fx+gx)) '2000)))))))))))) (defun interpolate-comp-k(data-type val fun1 fun2) ;(interpolate x1 x2 y1 y2 x3) (interpolate x1 x2 (eval (get fun1 data-type)) (eval (get fun2 data-type)) val)) (defun interpolate-mod-k(data-type val fun1 fun2) ;(interpolate x1 x2 y1 y2 x3) (interpolate x1 x2 (eval (get fun1 data-type)) (eval (get fun2 data-type)) val)) (defun interpolate-sg-dep(data-type val fun1 fun2) ;(interpolate x1 x2 y1 y2 x3) (interpolate x1 x2 (eval (get fun1 data-type)) (eval (get fun2 data-type)) val))
220 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
E.2 Slab Thickness ; All rights reserved © 2014 ELIAS YILMA. Licensed under the GPL. (defpackage :slab (:use :common-lisp ) #:slab #:thickness #:solve-for-d #:dd #:dl #:g #:cd #:drain #:sc #:k1 #:k2 #:k3 #:k4 #:k5 #:k6 #:k7 #:k8 #:k9 #:slab-thickness #:solve-thickness #:psi->kpa #:kpa->psi #:in->cm #:cm->in #:ft->m #:m->ft #:slab-top-level #:w18 #:reliability #:std-nor-dev #:*r-vs-zr* #:default #:psi #:ec) ;******************************************************** ****** ;DEFAULT VALUES ;******************************************************** ****** (setf dd 0.50) (defun dd(value) (setf dd value)) (setf dl 0.70) (defun dl(value) (setf dl value)) (setf g
0.05)
(defun g(value) (setf g value)) (setf cd 1.00) (defun drain(conditions) (setf cd (get conditions 'drainage))) (setf (setf (setf (setf (setf (setf
reliability 0.90) std-nor-dev -1.282) psi 2.00) tsl 2.5) ec 5000000) sc 650)
;++++++++++++++++++++++++++++++example+++++++++++++++++++ ++++++ ;k=72pci ;ec=5 * 10^6 psi ;s'c=650psi ;j=3.2 221 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
;cd=1.0 ;So=0.29 ;del.psi=1.7 ;r=95% (zn=-1.645) ;w18 = 5.1 * 10^6 (setf esal 14571428.57) (setf ec 5000000) (setf period 20) (setf g 0.04) (setf k-value 72)
;******************************************************** ****** ;PARAMETERS ;******************************************************** ****** ;traffic (defun esal() (setf esal (* w18-orig (/ (- (expt (+ 1 g) period) 1) g)))) (defun w18() (setf w18 (* dl dd esal))) ;reliability (setf (get 'i&of 'urban) 0.925) 'rural) 0.9) (setf (get 'pa 'urban) 0.9) 0.85) (setf (get 'coll 'urban) 0.875) 'rural) 0.85) (setf (get 'loc 'urban) 0.650) 'rural) 0.65)
(setf (get 'i&of (setf (get 'pa 'rural) (setf (get 'coll (setf (get 'loc
(defun reliability(road-funct road-loc) (setf reliability (get road-funct road-loc))) ;w18-orig period ;standard normal deviate (defun std-nor-dev(rel) (setf std-nor-dev (second (assoc rel *r-vs-zr*)))) (defparameter *r-vs-zr* '((0.925 -1.141) (0.90 -1.282) (0.875 -1.1595) (0.85 -1.037) 222 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
(0.65 -0.3885))) ;overall standard deviation (setf so 0.35) ;serviceability loss (setf (get 'default 'tsl) 2.5) (setf (get 'default 'isi) 4.5) (defun default(item) (get 'default item)) (defun psi(po pt) (setf psi (- po pt))) ;concrete elastic modulus (defun ec() (setf ec (* 57000 (sqrt fc)))) ;concrete modulus of rupture (defun sc(fc) (setf sc (* 7.5 (sqrt fc)))) ;j-factor (setf j-factor 3.2) ;drainage (setf (get 'excellent 1.15) 'drainage) (setf (get 'good 1.0875) 'drainage) (setf (get 'fair 1) 'drainage) (setf (get 'poor 0.9) 'drainage) (setf (get 'very-poor 0.8) 'drainage) ;******************************************************** ********** ;EVALUATE THE EQUATION (defun k1 () (setf k1 (log (w18) 10))) (defun k2() (setf k2 (* std-nor-dev so))) (defun k3() (setf k3 (* 7.35 (log (+ D 1) 10)))) (defvar k4 0.06) (defun k5() (setf k5 (log (/ psi (- 4.5 1.5)) 10))) (defun k6() (setf k6 (- 4.22 (* 0.32 tsl)))) (defun K7() (setf k7 (log (/ (* sc cd) (* 215.63 j-factor)) 10))) 223 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
;k-value is needed at k8. (defun k8() (setf k8 (log (/ (- (expt d 0.75) 1.132) (- (expt d 0.75) (/ 18.42 (expt (/ ec k-value) 0.25)))) 10))) (defun k9() (setf k9 (+ 1 (/ 1.624e7 (expt (+ d 1) 8.46))))) (defun slab-thickness() (+ (k2) (k3) k4 (/ (k5) (k9)) (* (k6) (+ (k7) (k8))))) (defvar *std-thicknesses* '(5 6 7 8 9 10 11 12)) (defun solve-for-d() (format t "log18 right-side delta ~%") (loop for std-thickness in '(5 6 7 8 9 10 11 12 13 15 17) do (setf d std-thickness) (k1) (let ((slab-thickness (slab-thickness))) (format t "~a ---- ~a ---- ~a ~%" k1 slab-thickness (- k1 slab-thickness))))) (defun solve-thickness() (k1) (setf a '()) (setf d 5) (setf slab-thickness 4) (format t "log18 right-side delta ~%") (loop until (< (- k1 slab-thickness) 0) do (setf d (+ 1 d)) (setf slab-thickness (slab-thickness)) (setf a (cons (list d k1 slab-thickness) a)) (format t "~a ---- ~a ---- ~a ~%" k1 slab-thickness (- k1 slab-thickness))) (setf a (nreverse a))) (defun slab-top-level() (k-value) ;(setf k-value (prompt "k-value: ")) (setf esal (prompt "~% ESAL : ")) (setf k-value effective-k) (setf fc (prompt "~% compressive strength of concrete :")) (solve-thickness) (rein-%) (setf file (prompt "file name: ")) 224 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
(test-table (first file)) (output)) (defun output() (format t "~%K-VALUE : ~a pci" k-value) (format t "~%SLAB THICKNESS : ~a in" d) (format t "~%REINFORCEMENT PERCENTAGE: ~a%" rein-%) (format t "~%REINFORCEMENT AREA PER UNIT WIDTH: ~asq.in." rein-a))
E.3 Reinforcement ; All rights reserved © 2014 ELIAS YILMA. Licensed under the GPL. (defpackage :rein (:use :common-lisp ) (:export #:rein-% #:fs)) ;reinforcement (defun rein-% () (setf f (prompt "friction factor: ")) (setf fs (prompt "steel working stress: ")) (setf l (prompt "length of slab: ")) (setf rein-% (* (/ (* f l) (* 2 fs)) 100)) (setf rein-a (* 12 rein-% d))) ;steel stress (defun fs() (setf fs (* 0.75 fy)))
E.4 PDF Output ; All rights reserved © 2014 ELIAS YILMA. Licensed under the GPL. ;CL-PDF © 2014 MATT BATTYANI ;CL-PDF hosted at https:/www.github.com/mbattyani/cl-pdf (load "c:/users/user/quicklisp/setup.lisp") (ql:quickload "cl-pdf") (ql:quickload "cl-typesetting") (defvar *months* '(january february march april may june july august september october november december)) (defun test-table (&optional (file "test-table12.pdf") &aux content table (margins '(72 72 72 50))) (let* ((row-height nil)) (tt:with-document () (setq content (tt:compile-text (:font (pdf:get-font "courier") :font-size 12) (tt:paragraph () "PAVEMENT DESIGN RESULTS") 225 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
(tt:paragraph () (tt:format-string "PROJECTED SLAB THICKNESS = ~a" pst)) (tt:paragraph () (tt:format-string "K-VALUE = ~a" effective-k)) (tt:paragraph () (tt:format-string "SUBBASE THICKNESS = ~a" sb-thickness)) (tt:paragraph () (tt:format-string "LOSS OF SUPPORT = ~a" ls)) (tt:paragraph () (tt:format-string "DEPTH TO RIGID FOUNDATION = ~a" sg-depth)) (tt:table (:col-widths '(73 60 60 70 70 60) :border 1) (tt:row (:height row-height) (tt:cell () "Month") (tt:cell () "Roadbed Modulus") (tt:cell () "Subbase Modulus") (tt:cell () "Composite Reaction") (tt:cell () "Modified Reaction") (tt:cell () "Relative Damage")) (loop for month in *months* do (tt::row (:height row-height ) (tt:cell (:row-span 2) (tt:format-string "~a" month)) (tt:cell () (tt:format-string "~a" (get 'rbsrm month))) (tt:cell () (tt:format-string "~a" (get 'sbrm month))) (tt:cell () (tt:format-string "~a" (get 'composite-k month))) (tt:cell () (tt:format-string "~a" (get 'modified-k month))) (tt:cell () (tt:format-string "~a" (get 'reldamage month)))) (tt::row (:height row-height ) (tt:cell () (tt:format-string "-" )) (tt:cell () (tt:format-string "-" )) (tt:cell () (tt:format-string "-" )) (tt:cell () (tt:format-string "-" )) (tt:cell () (tt:format-string "-" )))) (tt:row (:height row-height) (tt:cell (:col-span 5) (tt:format-string "SUMMATION OF RELATIVE DAMAGE, S(uf)= ~a" sum-uf)) (tt:cell () (tt:format-string "~a" 'r)))) (tt:paragraph () (tt:format-string "Average: SUM(UF)/NO. OF MONTHS = ~a" avg-uf)) (tt:paragraph () (tt:format-string "EFFECTIVE MODULUS OF SUBGRADE REACTION, k(pci) = ~a" rel-k-value)) (tt:paragraph () (tt:format-string "CORRECTED FOR LOSS OF SUPPORT, k(pci)= ~a" effective-k)) 226 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
(tt:table (:col-widths '(250 70) :border 1) (tt:row (:height row-height) (tt:cell () (tt:format-string "PARAMETERS")) (tt:cell () (tt:format-string "VALUES"))) (tt:row (:height row-height) (tt:cell () (tt:format-string "EQUIVALENT SINGLE AXLE LOAD,W18")) (tt:cell () (tt:format-string "~a" w18))) (tt:row (:height row-height) (tt:cell () (tt:format-string "RELIABILITY,R")) (tt:cell () (tt:format-string "~a" reliability))) (tt:row (:height row-height) (tt:cell () (tt:format-string "OVERALL STANDARD DEVIATION,So" )) (tt:cell () (tt:format-string "~a" std-nor-dev))) (tt:row (:height row-height) (tt:cell () (tt:format-string "DESIGN SERVICEABILITY LOSS,PSI")) (tt:cell () (tt:format-string "~a" psi))) (tt:row (:height (tt:cell () MODULUS,Ec")) (tt:cell () (tt:row (:height (tt:cell () RUPTURE,Sc")) (tt:cell () (tt:row (:height (tt:cell () COEFFICIENT,J")) (tt:cell () (tt:row (:height (tt:cell () (tt:cell () (tt:row (:height (tt:cell () (tt:cell () (tt:row (:height (tt:cell () STRESS,Fs")) (tt:cell () (tt:row (:height (tt:cell () (tt:cell ()
row-height) (tt:format-string "CONCRETE ELASTIC (tt:format-string "~a" ec))) row-height) (tt:format-string "CONCRETE MODULUS OF (tt:format-string "~a" sc))) row-height) (tt:format-string "LOAD TRANSFER (tt:format-string row-height) (tt:format-string (tt:format-string row-height) (tt:format-string (tt:format-string row-height) (tt:format-string
"~a" j-factor))) "K-VALUE,k")) "~a" effective-k))) "SLAB LENGTH,L")) "~a" l))) "STEEL WORKING
(tt:format-string "~a" fs))) row-height) (tt:format-string "FRICTION FACTOR,F")) (tt:format-string "~a" f))))
(tt:table (:col-widths '(70 100 100 100) :border 1) (tt:row (:height row-height) (tt:cell () (tt:format-string "trial D")) (tt:cell () (tt:format-string "left hand side")) (tt:cell () (tt:format-string "right hand side")) 227 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
(tt:cell () (tt:format-string "difference"))) (loop for i from 0 to (- (length a) 1) do (tt:row (:height row-height) (tt:cell () (tt:format-string "~a") (first (nth i a))) (tt:cell () (tt:format-string "~a") (second (nth i a))) (tt:cell () (tt:format-string "~a") (third (nth i a)))))) (tt:paragraph () (tt:format-string "SLAB THICKNESS, D = ~a inches" d)) (tt:paragraph () (tt:format-string "reinforcement % = LF/2Fs = ~a %" rein-%)) (tt:paragraph () (tt:format-string "reinforcemnt area = 12 * D * % =~a sq.in." rein-a)) )) (tt::draw-pages content :margins margins :break :after) (pdf:write-document file))))
E.5 Utilities ; All rights reserved © 2014 ELIAS YILMA. Licensed under the GPL. ;-------------------------isolation of variables----------------------; (defun variable-p (exp) "Variables are the symbols M through Z." (member exp '(x y z m n o p q r s t u v w))) (defun ex-p (x) (consp x)) (defun ex-args (x) (rest x)) (defun ex-lhs (exp1) (second exp1)) (defun ex-op (exp1) (first exp1)) (defun ex-rhs (exp1) (nth 2 exp1)) (defun mkex (ex-l ex-o ex-r) (list ex-o ex-l ex-r)) ;mktri identify-variables vars-in-exp var-in-exp (defun mktri (ex-t ex-e) (list ex-t ex-e)) (defun ex-t(ex) (first ex)) (defun ex-e(ex) (second ex)) 228 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
(defun inverse-trig-op(op) (second (assoc op *trig-inverses*))) (defparameter *trig-inverses* '((sin arcsin) (tan arctan) (cos arccos) (log exp))) (defun binary-ex-p (x) (and (ex-p x) (= (length (ex-args x)) 2))) (defparameter variables '(composite-k a b c d e f g h i j k l m n o p q r s t u v w x y z)) (defun identify-variables(list1) (cond ((null list1) nil) ((numberp list1) nil) ((and (atom list1) (member list1 variables)) list1) ((member list1 variables) list1) ((member (first list1) variables) (cons (first list1) (identify-variables (rest list1)))) ((atom (first list1)) (identify-variables (rest list1))) (t (cons (identify-variables (first list1)) (identify-variables (rest list1)))))) (defun flatten (l) (cond ((null l) nil) ((atom l) l) ((atom (car l)) (cons (car l) (flatten (cdr l)))) (t (append (flatten (car l)) (flatten (cdr l)))))) (defun vars-in-exp (list1) (flatten (identify-variables list1))) (defun var-in-exp (x list1) (cond ((eql x (vars-in-exp list1)) t) ((and (listp list1) (member x (vars-in-exp list1))) t) (t nil))) (defun one-unknown (list1) (if (= (length (vars-in-exp list1)) 1) (first (vars-inexp list1)) nil)) ;no-unknown isolate-var solve compute prefix->infix split ;*inv-ops* inverse-op (defun no-unknown (list1) (if (null(vars-in-exp list1)) t nil)) (defun isolate-var (e x) 229 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
(cond ((eql (ex-lhs e) x) e) ((var-in-exp x (ex-rhs e)) (isolate-var (mkex (ex-rhs e) '= (ex-lhs e)) x)) ((unary-ex-p (ex-lhs e)) (isolate-var (mkex (ex-e (ex-lhs e)) '= (mktri (inverse-trig-op (ex-t (ex-lhs e))) (ex-rhs e))) x)) ((var-in-exp x (ex-lhs (ex-lhs e))) (isolate-var (mkex (ex-lhs (ex-lhs e)) '= (mkex (exrhs e) (inverse-op (ex-op (ex-lhs e))) (ex-rhs (ex-lhs e)))) x)) ((commutative-p (ex-op (ex-lhs e))) (isolate-var (mkex (ex-rhs (ex-lhs e)) '= (mkex (exrhs e) (inverse-op (ex-op (ex-lhs e))) (ex-lhs (ex-lhs e)))) x)) (t (isolate-var (mkex (ex-rhs (ex-lhs e)) '= (mkex (ex-lhs (ex-lhs e)) (ex-op (ex-lhs e)) (ex-rhs e))) x)))) (defun solve(eqn x) (isolate-var (infix->prefix eqn) x)) (defun compute(eqn x) (cond ((not (null (vars-in-exp (ex-rhs (solve eqn x))))) (eval (ex-rhs (solve eqn x)))) (t "unknowns still exist within the eqn"))) ;inverse rules (defparameter *inv-ops* '((+ -) (- +) (* /) (/ *))) (defun inverse-op (op) (second (assoc op *inv-ops*))) (defun commutative-p(op) (member op '(+ - *))) ;--------------------------infix->prefix--------------------------------; (defun prefix->infix (exp1) "Translate prefix to infix expressions." (if (atom exp1) exp1 (mapcar #'prefix->infix (if (binary-ex-p exp1) (list (ex-lhs exp1) (ex-op exp1) (exrhs exp1)) exp1)))) (defun unary-ex-p (ex) (and (listp ex) (= (length ex) 2)))
230 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
(defun split (list index) (assert (prefix (defparameter *ops* '(= + - * / sine)) (defun op-succeedence(ex) (or (position (first *ops*) ex) (position (second *ops*) ex) (position (third *ops*) ex) (position (fourth *ops*) ex) (position (fifth *ops*) ex))) (defun nest-lists(ex) (let ((index (op-succeedence ex))) (cond (index (multiple-value-bind (before op after) (split ex index) (list (nest-lists before) op (nest-lists after)))) (t (car ex))))) (defun nest-trigon(lists) (cond ((endp lists) nil) ((not (member (car lists) *trig-ops*)) (cons (car lists) (nest-trigon (cdr lists)))) ( (member (car lists) *trig-ops*) (if (consp (second lists)) (cons (list (car lists) (nest-lists (second lists))) (nest-trigon (cddr lists))) (cons (list (car lists) (second lists)) (nesttrigon (cddr lists))))) (t (nest-trigon (cdr lists))))) (defparameter *trig-ops* '(tan tangent arctan arctangent cosine cos arccos arccosine log sin sine arcsine arcsin )) (defun prepare(ex) (cond ((unary-ex-p ex) (list (car ex) (infix->prefix (cdr ex)))) 231 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
((= (length ex) 1) (prepare (car ex))) ((prefix->infix (nest-lists ex))) (t "illegal exp"))) (defun infix->prefix(ex) (prepare (nest-trigon ex)))
232 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
APPENDIX F: Cost Breakdown, Takeoff And Boq F.1 Cost Breakdown Reinforced Concrete (C-35) 1
m
LABOUR HOURLY OUTPUT:
3
0.625
EQUIPMENT:
0.624
(B) Labour (1:02) Qty.
* Rate
Cost per Unit
5.00
270.00
1350.00
0.712
460.00
0.282 0.352 9.00
Labour by Trade
Unit
UF
Forman
1
0.10
38.46
3.85
327.52
G.Leader
1
0.25
24.04
6.01
368.00
103.78
DL
4
1.00
12.50
50.00
414.00 12.00
145.73 108.00
Helper Plant
1 1
1.00 1.00
19.23 24.04
19.23 24.04
Total = B
2035.02
Add for overhead and profit
= =
Manpower Unit Cost Total of (1:02) 103.13 Hourly output 0.625 =
4271.75 5339.69
/ hr
/ hr
(C) Equipment Cost (1:03)
** Indexed Hour. Cost
2035.02
m3
m3
Hourly Cost
Type of Equipment
No
UF
Hourly Rental
Tools
4
1
2.01
Concrete Plant
1
1
1200.00
Vibrator
2
1
42.36
Total =
103.13 C 165.00
=
= =
5339.70
Per
8.04 1200.00 84.72
1292.76
Equipment Unit Cost Total of (1:03) 1292.76 Hourly output 0.624 Birr
Hourly Cost
2071.73
m3
233 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
3.4) Formworks, a,b,c,d,e,f,g,h 1
LABOUR HOURLY OUTPUT:
m2
0.723
EQUIPMENT:
0.720
(B) Labour (1:02) Qty.
* Rate
Cost per Unit
Labour by Trade
0.25 1.30 1.50 0.50
70.00 2.00 8.00 2.00
17.50 2.60 12.00 1.00
Forman G.Leader DL Carpenter Helper
Unit
UF
** Indexed Hour. Cost
1 1 2 1 2
0.10 0.25 1.00 1.00 1.00
38.46 24.04 12.50 19.23 19.23
33.10
Total = B
33.10
Add for overhead and profit
= =
Manpower Unit Cost Total of (1:02) 92.55 Hourly output 0.723 =
172.27 223.95
m2
m2
/ hr
/ hr
(C) Equipment Cost (1:03) Hourly Cost 3.85 6.01 25.00 19.23 38.46
Type of Equipment Tools
No
UF
Hourly Rental
4
1
2.01
Total =
92.55 C
=
128.01
=
=
224.00
Per
8.04
8.04
Equipment Unit Cost Total of (1:03) 8.04 Hourly output 0.72 Birr
Hourly Cost
11.17
m2
234 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
3.5) Reinforcement Steel Bars, a,b,c,d,e,f,g 1 Kg
LABOUR HOURLY OUTPUT: EQUIPMENT:
11.500
(B) Labour (1:02) Qty. 1
* Rate 24.12
Cost per Unit 24.12
Labour by Trade Forman G.Leader
Unit 1 1
UF 0.10 0.25
** Indexed Hour. Cost 38.46 24.04
DL Bar bender
2 1
1.00 1.00
12.50 19.23
24.12
Total = B
24.12
Add for overhead and profit
= =
Manpower Unit Cost Total of (1:02) 54.09 Hourly output 11.5 =
29.00 37.70
11.500 Kg
Kg
/ hr
/ hr
(C) Equipment Cost (1:03) Hourly Cost 3.85 6.01
Type of Equipment Tools
No 1
UF 1
Hourly Rental 2.01
Hourly Cost 2.01
25.00 19.23
Total =
54.09 C
=
4.70
=
=
37.70
2.01
Equipment Unit Cost Total of (1:03) 2.01 Hourly output 11.5 Birr
Per
0.17
Kg
235 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
F.2 Bar Schedule Item
Position
Longitudinal Bars (20, 25 or 30 years design period) PCC Slab Longitudinal Bars (35 or 40 years design period) Reinforcement Transverse Bars (20, 25, 30, 35 & 40 years design period) Tie Bars At the road crown Load Transfer Dowel Bars Longitudinally
Shape
No of No of Bar Bars Diameter Members
Length
Dia 10
Dia 12
Dia 14
Dia 50
6
12
80
25
--
12000
--
--
5
14
80
25
--
--
10000
--
2 10
10 14
80 40
4 0.3
640 --
---
-120
---
10
50
80
0.46
--
--
--
368
Total length kg/m
640 12000 10120 368 0.6166667 0.888 1.2086667 15.416667
Total kg 394.66667 10656 12231.707 5673.3333
236 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
F.3 Takeoff Sheet Item No. LxWxH
Qty
25 4 0.39
Description I. Concrete Works C-35 Ordinary Portland Cement Concrete of D depth and 4 m slab width
80 3120 m3
2
Formwork Side Formwork of 50 cm thickness
1000 0.5 1000
1000 10 0.15
II Gravel Subbase Layer With additional shoulder of 1m on each side (I.e. 8m + 2m = 10m) and 150 mm thickness 1500 m3
1 1000 10 0.4 1
m2
With additional shoulder of 1m on each side (I.e. 8m + 2m = 10m) and 400 mm thickness 4000 m3
237 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
F.4 BOQ I. Concrete Works 1.1 C-35 Portland Cement Concrete Slab Ordinary Portland Cement Concrete of C35 grade laid on a prepared subbase, which is proportioned, mixed, installed and cured to the required standard 1.2 Reinforcement Bars 1.2.1 Deformed Reinforcement Steel Bars Transverse Bars of Diameter 10 Longitudinal Bars of Diameter 12 Longitudinal Bars of Diameter 14 Tie Bars of Diameter 14 1.2.2 Plain Reinforcement Steel Bars Dowel Bars of Diameter 50
Unit
Quantity
Rate
Amount
m3
3120
5339.7
16659864
kg kg kg kg
394.6667 10656 12086.67 145.04
37.7 37.7 37.7 37.7
14878.93333 401731.2 455667.3333 5468.008
kg
5673.333
37.7
213884.6667
1.3 Formwork Side Formwork of 50 cm Depth
m2
1000
223.95
223950
II. Granular Subbase beneath the PCC Slab 150 mm thick granular subbase 400 mm thick granular subbase
m3 m3
1500 4000
279.87 279.87
419805 1119480
238 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
APPENDIX G: ECONOMIC DETAIL OF FLEXIBLE PAVEMENT APPENDIX G I: BOQ Note: The price of Bitumen Macadam has been assumed to be 70% of asphaltic wearing course because macadam is somehow an inferior material compared to asphaltic concrete. Table G1: Initial Investment of flexible pavement for subgrade CBR 2% Item No. Description Unit Qty. Rate Amount (Birr) Pavement a. Carriageway 46cm thick Gravel Subbase Compaction to 96% of AACRA Test S-11 Test S-11 Density (Compacted layer thickness of maximum 150mm) 25cm thick Crushed Stone Base Course Compacted to 98% of AACRA Test S-11 density (maximum compacted layer thickness 150mm) Supply and spray MC- 30 Cut Back Asphalt Prime Coat application at a Rate of 1lit/m2 between dense bitumen macadam and Base Course.
1
2
3
m3
4,600
279.87
1,287,402.00
m3
2,500
750.30
1,875,750.00
Lit
10,000
44.00
440,000.00
9,589,000.00
4
supply 21.5cm close graded dense bitumen macadam
m3
1,720 5,575.00
5
Supply and apply RC-70 Tack Coat application at a Rate of 0.3 lit/m2 on every layer of bitumen macadam Dense Graded Asphaltic Concrete (AC) Wearing Course Compacted thickness of 50mm
Lit
2,400
44.00
105,600.00
m2
8,000
318.57
2,548,560.00
6
Grand Total
15,846,312.00
239 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
Item No.
Table G2: Initial Investment of flexible pavement for subgrade CBR 3% Description Unit Qty. Rate Amount (Birr) Pavement a. Carriageway 38cm thick Gravel Subbase Compaction to 96% of AACRA Test S-11 Test S-11 Density (Compacted layer thickness of maximum 150mm) 25cm thick Crushed Stone Base Course Compacted to 98% of AACRA Test S11 density (maximum compacted layer thickness 150mm) Supply and spray MC- 30 Cut Back Asphalt Prime Coat application at a Rate of 1lit/m2 between dense bitumen macadam and Base Course. supply 21 cm close graded dense bitumen macadam Supply and apply RC-70 Tack Coat application at a Rate of 0.3 lit/m2 on every layer of bitumen macadam Dense Graded Asphaltic Concrete (AC) Wearing Course Compacted thickness of 50mm
1
2
3
4 5
6
AAiT, SCEE
m3
3,800
279.87
1,063,506.00
m3
2,500
750.30
1,875,750.00
Lit
10,000
44.00
440,000.00
m3
1,680 5,575.00
9,366,000.00
Lit
2,400
44.00
105,600.00
m2
8,000
318.57
2,548,560.00
Grand Total
Item No.
1
2
15,399,416.00
Table G3: Initial Investment of flexible pavement for subgrade CBR 4% Description Unit Qty. Rate Amount (Birr) Pavement a. Carriageway 33cm thick Gravel Subbase Compaction to 96% of AACRA Test S-11 Test S-11 Density (Compacted layer thickness of maximum 150mm) 25cm thick Crushed Stone Base Course Compacted to 98% of AACRA Test S-11 density (maximum compacted layer
m3
3,300
279.87
923,571.00
m3
2,500
750.30
1,875,750.00
240 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
thickness 150mm)
3
4 5
6
Supply and spray MC- 30 Cut Back Asphalt Prime Coat application at a Rate of 1lit/m2 between dense bitumen macadam and Base Course. supply 19 cm close graded dense bitumen macadam Supply and apply RC-70 Tack Coat application at a Rate of 0.3 lit/m2 on every layer of bitumen macadam Dense Graded Asphaltic Concrete (AC) Wearing Course Compacted thickness of 50mm
Lit
44.00
440,000.00
8,474,000.00
Lit
1,520 5,575.0 0 2,400 44.00
m2
8,000
2,548,560.00
m3
10,000
Grand Total
Item No.
2
3
4 5
14,367,481.0 0
Table G4: Initial Investment of flexible pavement for subgrade CBR 5% Description Unit Qty. Rate Amount (Birr) Pavement a. Carriageway 30cm thick Gravel Subbase Compaction to 96% of AACRA Test S-11 Test S-11 Density (Compacted layer thickness of maximum 150mm) 25cm thick Crushed Stone Base Course Compacted to 98% of AACRA Test S-11 density (miximum compacted layer thickness 150mm) Supply and spray MC- 30 Cut Back Asphalt Prime Coat application at a Rate of 1lit/m2 between dense bitumen macadam and Base Course. supply 17 cm close graded dense bitumen macadam Supply and apply RC-70 Tack Coat application at a Rate of 0.3 lit/m2 on every layer of bitumen macadam
1
318.57
105,600.00
m3
3,000
279.87
839,610.00
m3
2,500
750.30
1,875,750.00
Lit
10,000
44.00
440,000.00
m3
1,360 5,575.00
7,582,000.00
Lit
2,400
44.00
105,600.00
241 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
6
AAiT, SCEE
m2
Dense Graded Asphaltic Concrete (AC) Wearing Course Compacted thickness of 50mm
8,000
318.57
Grand Total
Item No.
1
2
3
4 5
6
2,548,560.00
13,391,520.00
Table G5: Initial Investment of flexible pavement for subgrade CBR 6% Description Unit Qty. Rate Amount (Birr) Pavement a. Carriageway 26cm thick Gravel Subbase Compaction to 96% of AACRA Test S-11 Test S-11 Density (Compacted layer thickness of maximum 150mm) 25cm thick Crushed Stone Base Course Compacted to 98% of AACRA Test S-11 density (maximum compacted layer thickness 150mm) Supply and spray MC- 30 Cut Back Asphalt Prime Coat application at a Rate of 1lit/m2 between dense bitumen macadam and Base Course. supply 16cm close graded dense bitumen macadam Supply and apply RC-70 Tack Coat application at a Rate of 0.3 lit/m2 on every layer of bitumen macadam Dense Graded Asphaltic Concrete (AC) Wearing Course Compacted thickness of 50mm
m3
2,600
279.87
727,662.00
m3
2,500
750.30
1,875,750.00
Lit
10,000
44.00
440,000.00
7,136,000.00
Lit
1,280 5,575.0 0 2,400 44.00
m2
8,000
2,548,560.00
m3
Grand Total
318.57
105,600.00
12,833,572.0 0
242 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
Item No.
1
2
3
4 5
6
AAiT, SCEE
Table G6: Initial Investment of flexible pavement for subgrade CBR 7% Description Unit Qty. Rate Amount (Birr) Pavement a. Carriageway 23cm thick Gravel Subbase Compaction to 96% of AACRA Test S-11 Test S-11 Density (Compacted layer thickness of maximum 150mm) 25cm thick Crushed Stone Base Course Compacted to 98% of AACRA Test S-11 density (maximum compacted layer thickness 150mm) Supply and spray MC- 30 Cut Back Asphalt Prime Coat application at a Rate of 1lit/m2 between dense bitumen macadam and Base Course. supply 16.5cm close graded dense bitumen macadam Supply and apply RC-70 Tack Coat application at a Rate of 0.3 lit/m2 on every layer of bitumen macadam Dense Graded Asphaltic Concrete (AC) Wearing Course Compacted thickness of 50mm
m3
2,300
279.87
643,701.00
m3
2,500
750.30
1,875,750.00
Lit
10,000
44.00
440,000.00
7,359,000.00
Lit
1,320 5,575.0 0 2,400 44.00
m2
8,000
2,548,560.00
m3
Grand Total
Item No.
318.57
12,972,611.0 0
Table G7: Initial Investment of flexible pavement for subgrade CBR 8% Description Unit Qty. Rate Amount (Birr) Pavement a. Carriageway 20cm thick Gravel Subbase Compaction to 96% of AACRA Test S-11 Test S-11 Density (Compacted layer thickness of maximum 150mm)
1
105,600.00
m3
2,000
279.87
559,740.00
243 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
2
25cm thick Crushed Stone Base Course Compacted to 98% of AACRA Test S-11 density (maximum compacted layer thickness 150mm) Supply and spray MC- 30 Cut Back Asphalt Prime Coat application at a Rate of 1lit/m2 between dense bitumen macadam and Base Course. supply 16cm close graded dense bitumen macadam Supply and apply RC-70 Tack Coat application at a Rate of 0.3 lit/m2 on every layer of bitumen macadam Dense Graded Asphaltic Concrete (AC) Wearing Course Compacted thickness of 50mm
3
4 5
6
AAiT, SCEE
m3
2,500
750.30
1,875,750.00
Lit
10,000
44.00
440,000.00
m3
1,280 5,575.00
7,136,000.00
Lit
2,400
44.00
105,600.00
m2
8,000
318.57
2,548,560.00
Grand Total
Item No.
1
2
3
4 5
6
12,665,650.00
Table G8: Initial Investment of flexible pavement for subgrade CBR 9% Description Unit Qty. Rate Amount (Birr) Pavement a. Carriageway 20cm thick Gravel Subbase Compaction to 96% of AACRA Test S-11 Test S-11 Density (Compacted layer thickness of maximum 150mm) 25cm thick Crushed Stone Base Course Compacted to 98% of AACRA Test S-11 density (maximum compacted layer thickness 150mm) Supply and spray MC- 30 Cut Back Asphalt Prime Coat application at a Rate of 1lit/m2 between dense bitumen macadam and Base Course. supply 15.5cm close graded dense bitumen macadam Supply and apply RC-70 Tack Coat application at a Rate of 0.3 lit/m2 on every layer of bitumen macadam Dense Graded Asphaltic Concrete (AC) Wearing Course Compacted thickness of 50mm
m3
2,000
279.87
559,740.00
m3
2,500
750.30
1,875,750.00
Lit
10,000
44.00
440,000.00
m3
1,240 5,575.00
6,913,000.00
Lit
2,400
44.00
105,600.00
m2
8,000
318.57
2,548,560.00
244 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Grand Total
Item No.
1
2
3
4 5
6
12,442,650.00
Table G9: Initial Investment of flexible pavement for subgrade CBR 10% Description Unit Qty. Rate Amount (Birr) Pavement a. Carriageway 20cm thick Gravel Subbase Compaction to 96% of AACRA Test S-11 Test S-11 Density (Compacted layer thickness of maximum 150mm) 25cm thick Crushed Stone Base Course Compacted to 98% of AACRA Test S-11 density (maximum compacted layer thickness 150mm) Supply and spray MC- 30 Cut Back Asphalt Prime Coat application at a Rate of 1lit/m2 between dense bitumen macadam and Base Course. supply 15cm close graded dense bitumen macadam Supply and apply RC-70 Tack Coat application at a Rate of 0.3 lit/m2 on every layer of bitumen macadam Dense Graded Asphaltic Concrete (AC) Wearing Course Compacted thickness of 50mm
m3
2,000
279.87
559,740.00
m3
2,500
750.30
1,875,750.00
Lit
10,000
44.00
440,000.00
m3
1,200 5,575.00
6,690,000.00
Lit
2,400
44.00
105,600.00
m2
8,000
318.57
2,548,560.00
Grand Total
12,219,650.00
Table G10: Initial Investment of flexible pavement for subgrade CBR 10% to 15% Item No. Description Unit Qty. Rate Amount (Birr) Pavement a. Carriageway 18cm thick Gravel Subbase Compaction to 96% of AACRA Test S-11 Test S-11 Density (Compacted layer thickness of maximum 150mm)
1
m3
1,800
279.87
503,766.00
245 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
2
22.5cm thick Crushed Stone Base Course Compacted to 98% of AACRA Test S-11 density (maximum compacted layer thickness 150mm) Supply and spray MC- 30 Cut Back Asphalt Prime Coat application at a Rate of 1lit/m2 between dense bitumen macadam and Base Course. supply 14cm close graded dense bitumen macadam Supply and apply RC-70 Tack Coat application at a Rate of 0.3 lit/m2 on every layer of bitumen macadam Dense Graded Asphaltic Concrete (AC) Wearing Course Compacted thickness of 50mm
3
4 5
6
AAiT, SCEE
m3
2,250
750.30
1,688,175.00
Lit
10,000
44.00
440,000.00
m3
1,120 5,575.00
6,244,000.00
Lit
2,400
44.00
105,600.00
m2
8,000
318.57
2,548,560.00
Grand Total
Item No.
11,530,101.00
Table G11: Initial Investment of flexible pavement for subgrade CBR 15% to 30% Description Unit Qty. Rate Amount (Birr) Pavement a. Carriageway 16cm thick Gravel Subbase Compaction to 96% of AACRA Test S-11 Test S-11 Density (Compacted layer thickness of maximum 150mm) 20cm thick Crushed Stone Base Course Compacted to 98% of AACRA Test S-11 density (maximum compacted layer thickness 150mm) Supply and spray MC- 30 Cut Back Asphalt Prime Coat application at a Rate of 1lit/m2 between dense bitumen macadam and Base Course. supply 13cm close graded dense bitumen macadam
1
2
3
4
m3
1,600
279.87
447,792.00
m3
2,000
750.30
1,500,600.00
Lit
10,000
44.00
440,000.00
1,040 5,575.00
5,798,000.00
m3
246 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
5
Supply and apply RC-70 Tack Coat application at a Rate of 0.3 lit/m2 on every layer of bitumen macadam Dense Graded Asphaltic Concrete (AC) Wearing Course Compacted thickness of 50mm
6
AAiT, SCEE
Lit
2,400
44.00
105,600.00
m2
8,000
318.57
2,548,560.00
Grand Total
Item No.
Table G12: Initial Investment of flexible pavement for subgrade CBR> 30% Description Unit Qty. Rate Amount (Birr) Pavement a. Carriageway 0cm thick Gravel Subbase Compaction to 96% of AACRA Test S-11 Test S-11 Density (Compacted layer thickness of maximum 150mm) 15cm thick Crushed Stone Base Course Compacted to 98% of AACRA Test S-11 density (maximum compacted layer thickness 150mm) Supply and spray MC- 30 Cut Back Asphalt Prime Coat application at a Rate of 1lit/m2 between dense bitumen macadam and Base Course. supply 11cm close graded dense bitumen macadam Supply and apply RC-70 Tack Coat application at a Rate of 0.3 lit/m2 on every layer of bitumen macadam Dense Graded Asphaltic Concrete (AC) Wearing Course Compacted thickness of 50mm
1
2
3
4 5
6
10,840,552.00
m3
0
279.87 -
m3
1,500
Lit
10,000
m3
750.30 1,125,450.00
44.00
440,000.00
880 5,575.00 4,906,000.00
Lit
2,400
m2
8,000
Grand Total
44.00
105,600.00
318.57 2,548,560.00
9,125,610.00
247 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
APPENDIX G II: PERIODIC MAINTENANCE, YEARLY OVERLAY AND REHABILITATION DETAILS Year
2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040
Table G13: Recurring Costs of flexible pavement throughout Design Period Overlay Future Value Periodic Maintenance Sum Cumulative Sum w.r.t 2017 (Birr/km) Future Value w.r.t 2017 (Birr/km) 50000 50000 50000 54080 54080 104080 58492.928 2924646.4 2983139.328 3087219.328 63265.95092 63265.95092 3150485.279 66524.1474 66524.1474 3217009.426 69950.14099 3497507.049 3567457.19 6784466.617 73552.57325 73552.57325 6858019.19 77340.53077 77340.53077 6935359.721 81323.56811 4066178.405 4147501.973 11082861.69 85511.73186 85511.73186 11168373.43 89915.58605 89915.58605 11258289.01 94546.23874 4727311.937 4821858.176 16080147.19 99415.37003 99415.37003 16179562.56 104535.2616 104535.2616 16284097.82 108863.0214 5443151.071 5552014.092 21836111.91 113369.9505 113369.9505 21949481.86 118063.4665 118063.4665 22067545.33 27049284.67 122951.294 6147564.698 33319800.67 55387345.99 128041.4775 128041.4775 55515387.47 133342.3947 133342.3947 55648729.87 138862.7698 6943138.492 7082001.262 62730731.13 144611.6885 144611.6885 62875342.82 33131694.73 150598.6124 33282293.35 96157636.16 156833.395 7841669.749 7998503.144 104156139.3
Major Maintenance Future Value w.r.t 2017 (Birr/km)
248 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057
35437371.3
36640538.02
33649104.1
AAiT, SCEE
157884.1787 158942.0027 160006.9141 161078.9605 162158.1895 163244.6494 164338.3885 165439.4557 166547.9001 167663.771 163857.8034 160138.2313 156503.0934 152950.4732 149478.4975 146085.3356 142769.1984
8000345.707
8162232.469
8327395.004
8006911.563
7473924.873
157884.1787 158942.0027 8160352.621 35598450.26 162158.1895 8325477.118 164338.3885 165439.4557 45134480.92 167663.771 163857.8034 8167049.795 156503.0934 33802054.58 7623403.37 146085.3356 142769.1984
104314023.5 104472965.5 112633318.1 148231768.4 148393926.6 156719403.7 156883742.1 157049181.5 202183662.4 202351326.2 202515184 210682233.8 210838736.9 244640791.5 252264194.9 252410280.2 252553049.4
249 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Appendix H: Typical Flexible Pavement Section
250 BSc. Thesis
The Design of a Roadway Section from Adama to Awash using Rigid Pavement and its Implication in Ethiopian Road Construction
AAiT, SCEE
Appendix I: Typical RIGID Pavement Section
251 BSc. Thesis
