DESIGN OF MULTISTOREY BUILDING WITH COMPARISON OF ...

University of Technology, Sydney Faculty of Engineering and Information Technology

DESIGN OF MULTISTOREY BUILDING WITH COMPARISON OF REINFORCED CONCRETE AND CROSS LAMINATED TIMBER (CLT)

By Mootassem Hassoun

11615022

A15-041

Supervisor: Dr Rijun Shrestha

A 12 Credit Point Project submitted in partial fulfilment of the requirement for the Degree of Bachelor of Engineering November 2015

Statement of Originality I Mootassem Hassoun, declare that my group members and I (Osman El Zohbi, Omar El-Hawat and Mootassem Hassoun) are the sole authors of this report. No fragments of text from other sources have been used without proper acknowledgement. Theories, results and designs of others that have been incorporated into the report, have been appropriately referenced and all sources of assistance have been acknowledged.

Signed ____________________

Date ____________________

Abstract Design of Multistorey Building with comparison of Reinforced Concrete and Cross Laminated Timber (12cp) Mootassem Hassoun- A15-041 Supervisor: Dr Rijun Shrestha Assessor: Dr Yancheng Li Major: Civil Engineering Major BE and BE Dip Eng Prac

Due to expanding world population; cities have become more densely populated and are being pushed towards expansion of infrastructure starting with the construction of multi-storey and multi-residential dwellings. These types of construction are possible due to the accessibility of cheap and convenient building materials such as concrete and steel. However, new building materials such as Cross Laminated Timber (CLT) are striving to enter the construction industry to reduce labour costs and provide a more renewable source of construction materials which offer a similar strength in terms of properties.

CLT was initially developed in Europe and is becoming increasingly common since it is a suitable substitute to concrete. It is a new innovation to timber engineering as it offers enhanced properties at a cost-competitive price. Currently, Europe and New Zealand manufacture Cross Laminated Timber. Handbooks for CLT design are available from FP Innovations utilising American and European standards in their calculations. Designing buildings with CLT reduces construction time enormously as CLT is light in weight and simple to assemble making it an attractive material to use.

This group project aims to compare Cross Laminated Timber with Reinforced Concrete by assessing its feasibility as a construction material and its design properties while attempting to design an eight storey building. The project aims to research as well as learn about the intricate and detailed considerations needed to design a complex multi-storey building. This project will focus on utilising and learning how to use engineering software that is currently used in the industry to model and design the structure, as well as investigate the theory behind CLT.

Acknowledgments First and foremost, I would like to express my deepest appreciation to my supervisor Dr. Rijun Shrestha. Thank you for directing me with your knowledge and experience in many long discussions on various topics related to my Capstone. A special thanks for my wife Zahra Ali for supporting me throughout this thesis. I would also like to thank Mr. Zyad El Dekak (Lecturer at UTS: Insearch) for his generous time in motivating me and guiding my research with his deep knowledge in structural engineering. A great thanks to my wonderful group in helping me finish this big project, through their great participation and planning in this project. Finally, I would like to express my gratitude to my finally for their support and keeping up the good spirit. Great thanks to you all.

Mootassem Hassoun University of Technology, Sydney, November 2015

Table of Contents Statement of Originality ............................................................................................... 2 Abstract ........................................................................................................................ 3 Acknowledgments ........................................................................................................ 4 List of Figures ............................................................................................................ 12 List of Tables.............................................................................................................. 19 Nomenclature ............................................................................................................. 21 Chapter 1: Introduction ................................................................................................ 1 1.1 Motivation .......................................................................................................... 1 1.2 Objective ............................................................................................................ 3 1.3 Scope .................................................................................................................. 4 1.4 Overview of report ............................................................................................. 5 1.5 Group breakdown ............................................................................................... 6 1.6 Restraints ............................................................................................................ 8 1.7 Reflections .......................................................................................................... 9 1.7.1 Contribution ................................................................................................. 9 1.7.2 Group Structure and references ................................................................. 10 1.7.3 Management Structure ............................................................................... 11 1.7.4 Technical challenge ................................................................................... 12 1.7.5 Management challenge .............................................................................. 13 1.7.6 Group work lessons ................................................................................... 13 1.7.7 Responsibility matrix ................................................................................. 15 1.7.8 Time Budget .............................................................................................. 18 1.7.9 Milestones .................................................................................................. 21 Chapter 2: Concrete Design ...................................................................................... 23 2.1 Material Technology and Loading ................................................................... 24

2.1.1 Concrete Materials ..................................................................................... 24 2.1.2 Cement and Water ..................................................................................... 24 2.1.3 Aggregates ................................................................................................. 25 2.1.4 Concrete in Compression and Tension ...................................................... 26 2.1.5 Elastic Modulus of Concrete ..................................................................... 28 2.1.6 Reinforcement Steel .................................................................................. 28 2.2 General Design Requirements .......................................................................... 29 2.2.1 Ultimate Limit State (ULS) ....................................................................... 29 2.2.2 Serviceability Limit ................................................................................... 31 2.3 Reinforced Concrete Beams ............................................................................. 31 2.3.1 Ultimate Strength Theory .......................................................................... 31 2.3.2 Ultimate Strength of a Single Reinforced Rectangular Section ................ 34 2.3.3 Allowable Steel in Beam Section .............................................................. 35 2.3.4 Moment Capacity Equation ....................................................................... 36 2.3.5 Double Reinforced Rectangular Sections .................................................. 37 2.4 Design of Two-Way Transfer Slabs ................................................................. 39 2.4.1 Flat slab design .......................................................................................... 39 2.4.2 Slab Analysis ............................................................................................. 43 2.4.3 Design and Detailing of Flat Slabs ............................................................ 47 2.4.4 Deflection and Serviceability .................................................................... 48 2.5 Shear Walls ...................................................................................................... 50 2.5.1 Types of shear walls .................................................................................. 51 2.5.2 Architectural Aspects ................................................................................ 53 2.5.3 Failure Mechanisms ................................................................................... 54 2.5.4 Shear-Wall-Frame Interaction ................................................................... 57 2.5.5 Coupled Shear Wall ................................................................................... 58 2.5.6 Distribution of Forces ................................................................................ 60

2.5.7 Placement of Shear Walls .......................................................................... 65 2.5.8 Wall Reinforcement Design....................................................................... 66 2.5.9 Effective Height ......................................................................................... 68 2.5.10 Walls Designed as Columns .................................................................... 74 2.5.11 Reinforcement Layout ............................................................................. 75 2.6 Column ............................................................................................................. 76 2.6.1 Columns with central loading .................................................................... 76 2.6.2 Uniaxial bending of columns ..................................................................... 78 2.6.3 Biaxial bending .......................................................................................... 81 2.6.4 Short column design .................................................................................. 82 2.6.5 Slender columns ......................................................................................... 83 Chapter 3: Cross Laminated Timber

(CLT) ............................................................ 89

3.1 Cross Laminated Timber (CLT) ....................................................................... 90 3.2 CASE Study ..................................................................................................... 92 3.2.1 Forte Lend Lease ....................................................................................... 92 3.2.2 Stadthaus, Murray Grove ........................................................................... 94 3.2.3 XLam NZ ................................................................................................... 96 3.3 Environmental and Economic Benefits ............................................................ 97 3.4 CLT Analysis and Design ................................................................................ 98 3.4.1 Formulae .................................................................................................... 99 3.4.2 Mechanically Jointed Beams Theory (Gamma Method) ......................... 100 3.4.3 Composite Theory (K-method) ................................................................ 101 3.4.4 Shear Analogy Method (by Kreuzinger) ................................................. 103 3.4.5 Our Chosen Methods for Calculations..................................................... 104 3.4.6 Analysis of Timber Connections ............................................................. 105 3.4.7 Method of Design .................................................................................... 116 3.4.8 CLT Connection Structural Analysis ....................................................... 122

Chapter 4: Loading .................................................................................................. 123 Chapter 5: Computer Modelling and Design ........................................................... 127 5.1 ETABS Model ................................................................................................ 128 5.1.1 General Modelling ................................................................................... 128 5.1.2 Material Definition .................................................................................. 129 5.1.3 Sections Definition .................................................................................. 129 5.1.4 Floor Diaphragms .................................................................................... 131 5.1.5 Frame Connection.................................................................................... 131 5.1.6 Loadings .................................................................................................. 132 5.1.7 Concrete Frame and Shear Wall Design.................................................. 134 5.1.8 Analysis and Results ................................................................................ 137 5.1.9 Shear Wall Moments ............................................................................... 137 5.2 SAFE .............................................................................................................. 138 5.2.1 Background .............................................................................................. 138 5.2.2 Advanced Deflection Calculations .......................................................... 138 5.2.3 Modelling................................................................................................. 139 5.2.4 Deflection Checks.................................................................................... 139 5.2.5 Ultimate Limit State Design .................................................................... 139 5.3 CSI Column .................................................................................................... 140 5.4 CLT Modelling............................................................................................... 142 5.4.1 Background .............................................................................................. 142 5.4.2 Modelling the Frame ............................................................................... 142 5.4.3 Preliminary Member Sizing..................................................................... 143 5.4.4 Materials .................................................................................................. 143 5.4.5 Element Sections ..................................................................................... 144 5.4.6 Modelling Techniques ............................................................................. 144 5.4.7 Output results ........................................................................................... 146

5.4.8 CLT Design and Check............................................................................ 146 5.5 Foundation Design ......................................................................................... 147 5.5.1 RC Building Mat Foundation Design ...................................................... 148 5.5.2 CLT Building Foundation Design ........................................................... 151 5.5.3 Foundation Summary............................................................................... 152 Chapter 6: Manual Calculations ............................................................................... 155 6.1 Building Manual Analysis and Design ........................................................... 156 6.2 Flat slab .......................................................................................................... 156 6.2.1 Flat Slab Analysis .................................................................................... 156 6.2.2 Moment Calculation ................................................................................ 159 6.2.3 Reinforcement Design ............................................................................. 159 6.2.4 Serviceability Check ................................................................................ 160 6.3 Column Design ............................................................................................... 163 6.3.1 Column Analysis...................................................................................... 163 6.3.2 Design Column under Mmax* and N* ...................................................... 164 6.3.3 Construction of Column Interaction Diagram ......................................... 165 6.4 Shear Walls..................................................................................................... 168 6.4.1 Shear Walls Analysis ............................................................................... 168 6.4.2 Check Strength of the Wall ...................................................................... 171 6.4.3 Shear Design ............................................................................................ 171 6.5 Cross Laminated Timber ................................................................................ 173 6.5.1 Floor Panel ............................................................................................... 173 6.5.2 Wall Design ............................................................................................. 175 6.5.3 Fire Rating Design ................................................................................... 176 6.5.4 Connection Design ................................................................................... 177 6.5.4.1 Floor-to-floor panel connection ............................................................ 177 6.6 Raft Foundations ............................................................................................ 182

6.6.1 Traditional Rigid Method ........................................................................ 183 Chapter 7: Financial Plan ........................................................................................ 191 7.1 Financial Plan ................................................................................................. 192 7.2 Construction sequence.................................................................................... 193 7.2.1 Access to Construction site...................................................................... 193 7.2.2 Construction Set out ................................................................................ 194 7.2.3 Excavation and compaction ..................................................................... 194 7.2.4 Raft Slab Construction............................................................................. 195 7.2.5 Crane Installation ..................................................................................... 196 7.2.6 Scaffolding around Building ................................................................... 197 7.2.8 Construction of Building ......................................................................... 198 7.2.9 Cross Laminated Structure ...................................................................... 203 7.2.10 Installation of services (electricity and other works)............................. 208 7.2.11 Closure: Finished Product ..................................................................... 208 7.3 Duration of construction................................................................................. 209 7.3.1 Concrete Structure ................................................................................... 209 7.3.2 Cross Laminated Structure ...................................................................... 217 7.4. Cost of Labour and Services ......................................................................... 222 7.4.1 Services .................................................................................................... 222 7.4.2 Crane Tower ............................................................................................ 222 7.4.3 Scaffolding............................................................................................... 224 7.4.4 Required Labourers Onsite ...................................................................... 226 7.5 Cost of materials............................................................................................. 229 7.5.1 Concrete Structure ................................................................................... 230 7.5.2 Cross Laminated Structure ...................................................................... 232 7.6 Advantages and Disadvantages of Using CLT .............................................. 235 7.6.1 Advantages .............................................................................................. 235

7.6.2 Disadvantages .......................................................................................... 237 7.7 Comparison between CLT and Concrete ....................................................... 239 7.7.1 Time of Construction ............................................................................... 240 7.7.2 Labour and service hire............................................................................ 241 7.7.3 Structural advantages ............................................................................... 244 7.7.4 Cost of materials ...................................................................................... 245 7.7.5 Transportation of material ....................................................................... 247 7.7.6 Prefabrication of materials ....................................................................... 248 7.7.7 Australian standards ................................................................................. 249 7.7.8 Environmental aspects ............................................................................. 250 7.7.9 Safety ....................................................................................................... 251 7.7.10 Durability ............................................................................................... 252 7.8 Summary of Results ....................................................................................... 253 Conclusion and recommendations ........................................................................... 256 Structural .............................................................................................................. 257 Construction ......................................................................................................... 257 References ................................................................................................................ 260 Appendix A- Model input ........................................................................................ 267 Appendix B – Model output..................................................................................... 276 Appendix C –Transfer slabs SAFE model output. ................................................... 294 Appendix D-CLT model input ................................................................................. 303 Appendix E- CLT model output .............................................................................. 305 Appendix F- RAFT Slab Input Data to SAFE ......................................................... 310 Appendix G- Raft slab output form SAFE ............................................................... 312 Appendix H- Construction plans.............................................................................. 323

List of Figures Figure 2.1: water cement ratio configuration chart (Omfra 2009)............................. 25 Figure 2.2: Different grading of concrete (Google 2008) .......................................... 26 Figure 2.3: Concrete compressive strength vs age of concrete (Cement 2010)......... 27 Figure 2.4: Concrete stress vs strain (Google 2014) .................................................. 29 Figure 2.5: Concrete stress Block in beams (Chowdhury & Loo 2010) .................... 32 Figure 2.6: Reinforced concrete internal forces, strain diagram and stress diagram . 33 Figure 2.7: Strain distributions at the ultimate state (Chowdhury & Loo 2010) ....... 34 Figure 2.8: Stress and strain diagrams of singly reinforced beams (Chowdhury & Loo 2010) .......................................................................................................................... 36 Figure 2.9: Stress and strain distributions of a doubly reinforced beams. ................. 38 (UTS lecture notes) .................................................................................................... 38 Figure 2.10: Illustration of danger caused by punching shear failure (Google 2011)39 Figure 2.11: critical punching shear perimeter ( AS3600:2009 ) .............................. 40 Figure 2.12: Illustration of parameters b and a (Lim &Rangan 2015) ..................... 42 Figure 2.13: Illustration shear studs layout. ............................................................... 42 Figure 2.14: shear studs placement in practice (Google 2015) ................................. 43 Figure 2.15: Width of design strips. (AS3600-2009) ................................................ 44 Figure 2.17: Column strip distribution....................................................................... 46 Figure 2.16: Middle strip distribution factors. ........................................................... 46 Figure 2.18: shear wall layout in the proposed model. .............................................. 50 Figure 2.19: shear walls types of deformation (Google 2012) .................................. 51 Figure 2.20: Typical shear wall-frame type configuration (Wight 2009) .................. 52 Figure 2.21: preferred shear walls plan layout. (Google 2012) ................................. 54 Figure 2.22: Types of shear walls failure (Russel 2015) ........................................... 55 Figure 2.23: Shear wall failure in Nepal (Google 2015) ........................................... 56 Figure 2.24: flexural shear wall failure (Google 2015) ............................................. 56 Figure 2.25: shear failure in shear walls. (Google 2015) ........................................... 57 Figure 2.26: Analysis of shear wall frame (Wight 2009) .......................................... 58 Figure 2.27: Types of shear walls-frame deformations (Google 2014) ..................... 58 Figure 2.28: Hinged versus stiff coupled shear walls. (Wight 2009) ........................ 59 Figure 2.29: Analysis of shear walls coupling beam. (Wight 2009) ......................... 60

Figure 2.30: Ieq values in different wall configurations (PCA 2009)........................ 61 Figure 2.31: Method of calculating effective flange width. (PCA 2009) .................. 63 Figure 2.32: difference between centre of rigidity and centre of mass. (Wight 2009) .................................................................................................................................... 64 Figure 2.33: Different shapes of shear walls. (Google 2014) .................................... 65 Figure 2.34: Different shear walls configurations within a plan. ............................... 65 Figure 2.35: Location of the critical shear section. (Wight 2009) ............................. 68 Figure 2.36: Buckling of two-edge restrained walls vs four-edge restrained walls. (Doh 2010) .......................................................................................................................... 69 Figure 2.37: Stress and strain in buckled shear wall .................................................. 72 Figure 2.38: Edge columns supporting high rise floor system................................... 76 Figure 2.39: A column loaded through its plastic centroid. (Loo 2010) .................... 77 Figure 2.40: Strain and stress diagrams in eccentrically loaded columns. (Loo 2010) .................................................................................................................................... 78 Figure 2.41: Strain and stress diagrams in different stages of columns loading ........ 80 Figure 2.42: Column interaction diagram. (Slideshare 2012) .................................... 81 Figure 2.43: Limitation for line of action of resultant axial force in a rectangular column. (AS3600) ...................................................................................................... 82 Figure 2.44: Definitions of variable for a short column. (AS3600) ........................... 83 Figure 2.45: Effective length factor for columns with simple end conditions. (AS3600) .................................................................................................................................... 84 Figure 2.46: Effective length factor for braced column. (AS3600) ........................... 86 Figure 2.47: Effective length factor for sway column. (AS3600).............................. 87 Figure 3.1: CLT single and double layer cross sections. (FPinnovation 2011) ......... 90 Figure 3.2: Standard CLT panel (assume section B-B is longitudinal). (FPinnovation 2011) .......................................................................................................................... 90 Figure 3.3: CLT and GLT. (FPinnovation 2011) ....................................................... 91 Figure 3.4: pictures showing the construction of Forte building. .............................. 92 Figure 3.5: 3-D model of forte. .................................................................................. 92 Figure 3.6: Stadthaus building. .................................................................................. 94 Figure 3.7: Stadthaus building construction (Trada 2012)......................................... 94 Figure 3.8: CLT transverse and longitudinal layers.( FPinnovation 2011) ............... 99 Figure 3.9: Rolling shear action between the CLT layers.(FPinnovation 2011) ....... 99 Figure 3.10: Typical geometry of CLT cross section.( FPinnovation 2011) ........... 104

Figure 3.11: Two way bending of CLT panels.( FPinnovation 2011) ..................... 105 Figure 3.12: Self tapping screws installation an shape.( FPinnovation 2011) ......... 107 Figure 3.13: Nail plate test.( FPinnovation 2011).................................................... 107 Figure 3.14: Timber Dowel. (FPinnovation 2011) .................................................. 108 Figure 3.15: Different connection points in typical CLT structure. (FPinnovation 2011) ........................................................................................................................ 108 Figure 3.16: Double spline connection (Egmond 2011) .......................................... 109 Figure 3.17: Surface spline connection (Egmond 2011) ......................................... 110 Figure 3.18: Half-lapped joint connection (Egmond 2011) ..................................... 110 Figure 3.19: Self tapping screws connection. (FPinnovation 2011) ........................ 112 Figure 3.20: Metal bracket connection at point B (FPinnovation 2011) ................. 113 Figure 3.21: Metal bracket connection at point C (FPinnovation 2011) ................. 114 Figure 3.22: Wall-to-roof connection.(FPinnovation 2011) .................................... 114 Figure 3.23: CLT connection to the foundation. (Egmond 2011) ........................... 115 Figure 3.24: Metal brackets installed on-site (Egmond 2011) ................................. 116 Figure 3.25: Geometry of Surface spline connection. (Storaenso 2014) ................. 119 Figure 3.26: Shear action of half-lapped joint connection (Storaenso 2014) .......... 120 Figure 3.27: Shear action on double lap joint (Storaenso 2014).............................. 121 Figure 3.28: Long section of the double lap joint. (Storaenso 2014) ...................... 122 Figure 5.1: ETABS model of the proposed building (ETABS 2015) ...................... 128 Figure 5.2: Floor diaphragm assignment in ETABS . ............................................. 131 Figure 5.3: Screenshot of ETABS output for column design. (ETABS 2015) ........ 135 Figure 5.4: Screenshot of ETABS output for Wall design. (ETABS 2015) ............ 136 Figure 5.5: Slab modelling in SAFE. (SAFE 2015) ................................................ 139 Figure 5.6: Punching shear calculation sheet as produced by SAFE. (SAFE 2015) 140 Figure 5.7: Shows the position of the neutral axis in the section. (CSI column)..... 141 Figure 5.8: Shows the stress values in the bars. (CSI column) ................................ 141 Figure 5.9: Typical CLT floor plan. (ETABS 2015) ............................................... 142 Figure 5.10: The spreadsheet program used to design CLT. ................................... 143 Figure 5.11: Full CLT model in ETABS 2015.(ETABS 2015) ............................... 145 Figure 5.12: The layout of the Mat foundation.(SAFE 2015) ................................. 148 Figure 5.13: Shows the column and design strips distribution in the slab.( ............ 149 Figure 5.14: CLT foundation layout. (SAFE 2015) ................................................. 151 Figure 6.1: Design strips layout. .............................................................................. 157

Figure 6.2: Column strip distribution factors. .......................................................... 158 Figure 6.3: Middle strip distribution factors. ........................................................... 159 Figure 6.4: bending moment diagram in column and middle strip. ......................... 160 Figure 6.5: serviceability bending moment distribution factors. ............................. 161 Figure 6.6: Bending moment diagram at serviceability. .......................................... 161 Figure 6.7: Column strip section at mid-span. ......................................................... 162 Figure 6.8: Tributary area distribution for each column. ......................................... 163 Figure 6.9: Column interaction diagram. ................................................................. 167 Figure 6.10: Shear walls layout. ............................................................................... 168 Figure 6.11: Applied forces, shear force and bending moment diagrams on the wall. .................................................................................................................................. 170 Figure 6.12: Wall interaction diagram per meter run. .............................................. 171 Figure 6.13: CLT cross section layout. .................................................................... 173 Figure 6.14: Internal forces in the CLT floor cross section. .................................... 174 Figure 6.15: Effect of 90min of fire exposure on the CLT section. ......................... 177 Figure 6.16: Various geometry of screws supplied in the market. .......................... 180 Figure 6.17: Floor to wall connection geometry. ..................................................... 181 Figure 6.18: Typical raft slab configuration. ........................................................... 183 Figure 6.19: Raft slab load balancing. ..................................................................... 183 Figure 6.20: Applied loads on the structure. ............................................................ 184 Figure 6.21: Load balancing on the design strip. ..................................................... 187 Figure 6.22: Bending moment diagram. Obtained from Microstran. ...................... 187 . ................................................................................................................................. 187 Figure 6.23: Shear force diagram. Obtained from Microstran. ................................ 187 Figure 7.1: Cross-laminated Multi-Dwelling building in New Zealand .................. 192 Figure 7.2: Establishing Access to sight for workers and machinery ..................... 193 Figure 7.3: Shows a surveyor using a total station to set out marks for the construction set out. ...................................................................................................................... 194 Figure 7.4: Excavation works being carried out ...................................................... 195 Figure 7.5: Excavation works being carried out ...................................................... 196 Figure 7.6: Initial construction of crane, being attached to slab .............................. 197 Figure 7.7: Scaffolding around structure ................................................................. 198 Figure 7.8: Placement of formwork for the concrete columns which are ready to be poured. ..................................................................................................................... 199

Figure 7.9: Conventional steel formwork used to set out walls............................... 200 Figure 7.10: The underside formwork and false work of the slabs in the concrete . 201 Figure 7.11: Curing of concrete by spraying a chemical compound. ...................... 202 Figure 7.12: Concrete crane truck pumping concrete to the upper levels of the building. .................................................................................................................................. 203 Figure 7.13: manufacturing of CLT timber to the appropriate size and measurements. .................................................................................................................................. 204 Figure 7.14: Mobile crane moving the CLT wall panel........................................... 205 Figure 7.15: connection of CLT slab sheets ............................................................ 206 Figure 7.16: connection between CLT column and Concrete Raft slab. ................. 206 Figure 7.17: connection between CLT wall panels using nail plates ...................... 207 Figure 7.18: Diagram shows the construction of a multistorey CLT building. ....... 208 Figure 7.19: Comparison of the time of construction of the eight storey building for both Cross-laminated timber and Concrete.............................................................. 241 Figure 7.20: Comparison for the cost of labour ....................................................... 243 Figure 7.21: Comparison for the cost of services .................................................... 244 Figure 7.22: The total estimated cost of the materials ............................................. 246 Figure 7.23: The total estimated cost of the materials ............................................. 247 Figure 7.24: Shows the percentage of CO2 emissions. ............................................ 250 Figure 7.25: Shows the Comparison of the costs associated with the construction of the CLT and concrete multistorey building. ............................................................ 253 Figure A.1: Model initialisation tab in ETABS . ..................................................... 267 Figure A.2: Creating the grid for the model in ETABS . ......................................... 267 Figure A.3: Concrete material property input in ETABS . ...................................... 268 Figure A.4: Concrete material strength input in ETABS . ....................................... 269 Figure A.6: Steel material strength input in ETABS . ............................................. 270 Figure A.5: Steel material property input in ETABS . ............................................ 270 Figure A.8: Column property stiffness modification factors in ETABS . ............... 271 Figure A.7: Column cross section input to ETABS . ............................................... 271 Figure A.9: Frame section property reinforcement data input into ETABS . .......... 272 Figure A.11: Slab property stiffness modification factors input to ETABS . .......... 273 Figure A.10: Slab property data input to ETABS . .................................................. 273 Figure A.12: Wall property input to ETABS . ......................................................... 273 Figure A.13: Wall property stiffness modification factors input to ETABS . ......... 274

Figure A.14: Wind load factors input to ETABS . ................................................... 274 Figure A.15: Ultimate load combinations input to ETABS . ................................... 274 Figure A.16: Strength reduction factors input to ETABS . ...................................... 275 . ................................................................................................................................. 275 Figure B.2: Myy at elevation A output from ETABS . ............................................. 277 Figure B.3: Mxx at elevation B output from ETABS . ............................................. 278 Figure B.4: Myy at elevation B output from ETABS . ............................................. 279 Figure B.5: Mxx at elevation C output from ETABS . ............................................. 280 Figure B.6: Myy at elevation C output from ETABS . ............................................. 281 . ................................................................................................................................. 281 Figure B.7: Mxx at elevation D output from ETABS . ............................................. 282 Figure B.8: Myy at elevation D output from ETABS . ............................................. 283 Figure B.9: Mxx at elevation E output from ETABS ............................................... 284 Figure B.10: Myy at elevation E output from ETABS . ............................................ 285 Figure B.11: Mxx at elevation F output from ETABS . ............................................ 286 Figure B.12: Myy at elevation F output from ETABS . ............................................ 287 Figure B.13: Base axial force on the columns output from ETABS . ...................... 288 Figure B.14: My- in shear walls for 1.2G+1.5Q output from ETABS . .................. 289 Figure B.15: Mx in shear walls for 1.2G+0.4Q-Wy output form ETABS . ............ 290 Figure B.16: Mx in shear walls 1.2G+0.4Q-Wx output from ETABS . .................. 291 Figure B.17: Axial force in shear walls output from ETABS . ................................ 292 Figure B.18: Column check and steel results output from ETABS . ....................... 293 Figure C.1: Approximate defection of the cracked slab output from SAFE. ........... 294 Figure C.2: Slab forces/stresses control tab in SAFE. ............................................. 295 Figure C.3: Slab moment intensities in the y-direction output from SAFE. ............ 296 Figure C.4: Slab moment intensities in the x-direction output from SAFE. ............ 297 Figure C.5: Slab top Reinforcement intensities in the y-direction output from SAFE. .................................................................................................................................. 298 Figure C.6: Slab top Reinforcement intensities in the x-direction output from SAFE. .................................................................................................................................. 299 . ................................................................................................................................. 299 Figure C.7: Slab bottom Reinforcement intensities in the y-direction output from SAFE. ....................................................................................................................... 300

Figure C.8: Slab bottom Reinforcement intensities in the y-direction output from SAFE. ....................................................................................................................... 301 Figure C.9: Slab punching shear check output from SAFE. .................................... 302 Figure D.2: Material properties strength input to ETABS . ..................................... 303 Figure D.1: Material properties input to ETABS .................................................... 303 Figure D.3: CLT floor panel input to ETABS . ....................................................... 304 Figure D.4: CLT wall panel input to ETABS .......................................................... 304 Figure E.1: CLT floor panel moment diagrams output form ETABS . ................... 305 Figure E.2: CLT floor panel shear diagrams output form ETABS . ........................ 306 Figure E.3: Walls moment diagrams with 1.2G+1.5Q output form ETABS .......... 307 Figure E.4: Walls axial force with 1.2G+1.5Q output form ETABS . .................... 308 Figure E.5: Walls shear diagram with 1.2G+1.5Q output form ETABS . ............... 309 Figure F.2: Stiff plate property data input to ETABS . ............................................ 310 Figure F.1: Raft slab property data input to ETABS . ............................................. 310 Figure F.3: Soil subgrade property data input to ETABS . ...................................... 311 Figure G.1: Bearing pressure on the soil under the foundation. .............................. 312 Figure G.2: Mx per meter run output from SAFE. .................................................. 313 Figure G.3: My per meter run output from SAFE. .................................................. 314 Figure G.4: Reinforcement per meter run in the x-direction output from SAFE. ... 315 Figure G.5: Reinforcement per meter run in the y-direction output from SAFE. ... 316 Figure G.6: Punching shear check output from SAFE. ........................................... 317 Figure G.7: Soil bearing pressure under the CLT foundation output from SAFE. .. 318 Figure G.8: CLT Raft bending moment diagram in the y-direction output from SAFE. .................................................................................................................................. 319 Figure G.9: CLT Raft bending moment diagram in the x-direction output from SAFE. .................................................................................................................................. 320 Figure G.10: CLT Raft Reinforcement in the x-direction output from SAFE......... 321 Figure G.11: CLT Raft Reinforcement in the y-direction output from SAFE......... 322

List of Tables Table 2.1: Mechanical properties of concrete ............................................................ 28 Table 2.2: Values of ф for strength design using elastic analysis .............................. 30 Table 2.3: Design moment factors for an end-span. .................................................. 45 Table 2.4: Design moment factors for an interior span. ............................................. 45 Table 2.5: Distribution of bending moment within the design strip. ......................... 46 Tabel 2.6: Fixity factor values. (AS3600) .................................................................. 85 Table 3.1: Characteristic Strength Values. (AS1720.1-2010) ................................... 96 Table 3.2: Properties of timber grades as presented in AS1720.1 and New Zealand timber properties. (Xlam 2014) .................................................................................. 97 Table 3.3: Values of the composition factors “k”. (Blass 2004) .............................. 102 Table 3.4: CLT effective strength and stiffness. (Blass 2004)................................. 103 Table 3.5: Table 4.3(A) from AS1720, where na is the number of rows of fasteners. (AS 1720.1-2011)..................................................................................................... 117 Table 4.1: values of unit weight of materials used in the model.............................. 124 Table 4.2: Values of super imposed dead load. ....................................................... 124 Table 5.1: Material input to ETABS . ...................................................................... 129 Table 5.2: Column’s properties input into ETABS . ................................................ 130 Table 5.3: Slab’s properties input into ETABS . ..................................................... 130 Table 5.4: Wall’s properties input into ETABS . ..................................................... 130 Table 5.5: Wind input parameters into ETABS . ..................................................... 133 Table 5.6: Recommended steel in the x-direction. ................................................... 150 Table 5.7: Recommended steel in the y-direction. ................................................... 150 Table 5.8: Recommended steel in the x-direction for CLT Raft.............................. 151 Table 5.9: Recommended steel in the y-direction in the CLT Raft. ........................ 152 Table 5.10: Foundation summary for the RC-Building Raft. .................................. 152 Table 5.11: Foundation summary for the CLT-Building Raft. ................................ 153 Table 6.1: Design moment factors for an end-span (AS3600-2009) ....................... 158 Table 6.2: Design moment factors for an interior span. ........................................... 158 Table 6.3: Distribution of bending moment within the design strip (AS3600-2009) .................................................................................................................................. 158 Table 6.4: Screw specifications................................................................................ 178 Table 6.5: characteristic withdrawal strength calculation sheets. ............................ 179

Table 6.6: loads applied on the design strip. ............................................................ 186 Table 6.7: Average soil pressure under the design strip. ......................................... 186 Table 7.1: Detailed breakdown structure ................................................................. 217 Table 7.2: Detailed breakdown structure of CLT building ...................................... 221 Table 7.4: Estimated cost of hiring Favco 500 Crane for the construction of CLT building .................................................................................................................... 224 Table 7.3: Estimated cost of hiring Favco 500 Crane for the construction of Concrete building .................................................................................................................... 223 Table 7.5: Estimated cost of hiring Scaffolding ...................................................... 225 Table 7.6: Estimated cost of hiring Scaffolding for CLT ........................................ 225 Table 7.7: Average rate of hire for labourers ........................................................... 226 Table 7.8: Estimated total labour costs for concrete ................................................ 227 Table 7.9: Average rate of hire for labourers in CLT .............................................. 228 Table 7.10: Estimated total labour costs for the construction of the CLT building. 229 Table 7.11: Average rate of cost for the materials ................................................... 230 Table 7.12: Estimated cost of all the materials ........................................................ 232 Table 7.13: Estimated concrete and steel costs for CLT ......................................... 233 Table 7.15: Estimated costs for the Steel brackets and self-tapping screws ............ 234 Table 7.14: Estimated CLT costs for the construction of the CLT building ........... 234 Table 7.16: Density of CLT and Concrete ............................................................... 245 Figure 7.17: Average rates/cost of the main materials ............................................ 246

Nomenclature 𝐴 𝑠𝑡 = cross sectional area of longitudinal tensile reinforcement; or (concrete) = cross-sectional area of reinforcement in the zone that would be in tension under the design loads if the effects of prestress and axial loads are ignored (concrete) Avs = cross sectional area of row of studs in the slab strip Avt = cross sectional area of row of studs in the torsion strip bw = web depth Cdyn = Dynamic response factor Cfig = Aerodynamic shape factor Cp,n = Net pressure coefficient acting normal to the surface for canopies, freestanding roofs, walls, etc. Cult = Compressive Force at ultimate state d = depth or vertical dimension of the member (timber) = effective section of a cross-section in the plane of bending; or (concrete) = nominal internal diameter of reinforcement bend or hook (concrete) Dchar = Remaining cross section thickness excluding charred thickens Dfire = effective cross section thickness used in calculating the CLT resistance dheat = Depth of heated zone which is assumed to have zero strength dom = mean value of do, averaged around the critical shear perimeter (concrete) Ds = overall depth of a slab or drop panel; or (concrete) = the member depth at the theoretical cut-off point or debonding point (concrete) ds = distance from loaded edge; or (timber) = depth of tapered beam at the smallest end (timber) = overall dimension measured between centre-lines of the outermost fitments (concrete) e = eccentricity of prestressing force or load; or (concrete) = the base of Napierian logarithms (concrete) ea = an additional eccentricity (concrete) EIeff = Effective flexural strength (timber)

𝐸𝑐 = Mean value of the modulus of elasticity of concrete at 28 days (concrete) f’c = Characteristic compressive (cylinder) strength of concrete at 28 days (concrete) = Characteristic value in compression (timber) fcv = Concrete shear strength (concrete) Fd = Uniformly distributed design load, factored for strength or serviceability, as appropriate (concrete) Fd.ef = Effective design service load per unit length or area, used in serviceability design (concrete) fh,1,k = Characteristic embedment strength fvy = Yield strength of the studs 𝑓𝑐𝑚𝑖 = Mean value of the in situ compressive strength of concrete at the relevant age (concrete) ′ 𝑓𝑐𝑡.𝑓 = Characteristic flexural tensile strength of concrete at 28 days (concrete)

𝑓𝑠𝑦 = Characteristic yield strength of reinforcement (concrete) GAeff = Effective shear stiffness Hw – floor-to-floor unsupported height of a wall (concrete) Ig = Gross moment of inertia Ieq = Equivalent moment of inertia K = A factor that accounts for the position of the bars being anchored with respect to the transverse reinforcement (concrete) k1 = Factor for load duration (timber) k13 = Factor for end grain effects (timber) k14 = Factor for effect of double shear (timber) k16 = Factor for plywood or metal side plates (timber) k17 = Factor for multiple fastener effect (timber) k3 = Deflection factor k4 = Factor for in-service absorption or desorption of moisture by timber (timber) Ka = Area reduction factor (Wind) Kc = Combination factor (Wind) kcs = Factor used in serviceability design to take account of the long-term effects of creep and shrinkage (concrete) Kl = Local pressure factor (Wind)

Ks = Soil subgrade modulus Kt = Shear stud factor ku = Neutral axis parameter being the ratio, at ultimate strength under any combination of bending and compression, of the depth to the neutral axis from the extreme compressive fibre to d (concrete) kuo = Ratio, at ultimate strength, without axial force of the depth to the neutral axis from the extreme compressive fibre to do (concrete) Kus = Slip modulus of self-tapping screws 𝑘𝑢𝑏 = Balanced neutral axis multiplier Lef = Effective span of a member, taken as the lesser of (Ln + D) and L for a beam or slab, or (concrete) = Ln + D/2 for a cantilever (concrete) Lo = L minus 0.7 times the sum of the values of asup at each end of the span (concrete) Lt = Width of the design strip 𝐿′𝑜 = The shorter length in the adjoining spans Lw = Length of the wall 𝑀𝐿.𝑠 = moment applied on the left of support 𝑀𝑀.𝑠 = moment applied on the middle span 𝑀𝑅.𝑠 = moment applied on the right support 𝑀𝑉∗ = unbalanced moment in flat slabs Md = Design capacity of a member in bending (timber) Mo = Total static moment = Moment at the base of the wall due to factored lateral loads Ms = Shielding multiplier Mt = Topographic multiplier Mw1 = Moment at the base of the wall 1 Mw2 = Moment at the base of the wall 2 MyRk = moment yield strength of the timber screw 𝑀𝑢 = Ultimate Moment of the section Mz.cat = Terrain/ height multiplier n = Number of spans of a multi-span roof

Nu = Ultimate strength of the wall per unit meter P = Annual probability of exceedance pw= Ratio of horizontal reinforcement area to the cross sectional area of the wall per meter run. qG= Dead load qQ= Live load S = Side wall = Slenderness coefficient (timber) T = Tensile force in the steel tw = Wall thickness u = punching shear perimeter Vdes,θ strength = Design wind speed VR = Regional wind speed Vu = Shear capacity 𝑉 ∗ = Applied shear force Vuo = Punching shear capacity yb = Distance form bottom of section to centroidal axis Z = Section modulus about the axis of bending βh = Ratio of width to thickness of column γi = Measurement of connection rigidity Δ = Total of the flexure and shear deflections in the wall 𝛥𝑙 = Long term deflection 𝛥𝑠 = Short term deflection Δtot = Total deflection σcr = cracking stress in concrete Φ = Capacity reduction factor Ψl = Factor for determining long term values of actions Ψs = Factor for determining short term values of actions 𝛼2 = Stress modification factor in concrete stress block ∗ 𝜀𝑐𝑠 = long term creep value for sydney

𝜀𝑐𝑢 = Ultimate compressive strain in concrete

𝜀𝑠𝑦 = yield strain in steel reinforcement 𝛾 = The ratio, under design bending or design combined bending and compression, of the depth of the assumed rectangular compressive stress block to kud 𝜌 = Density of material

Chapter 1: Introduction

Capstone B


Researched by: Osman El-Zohbi Written by: Osman El-Zohbi

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1.1 Motivation As world population grows and urban areas become more densely populated; high rise structures are becoming more and more common. In order to demonstrate competency as an engineer, it is necessary to be able to design different structures including multistorey dwellings. Design of high rise structures is a process that requires specialty knowledge that normally is neither taught nor publicly available. Additionally, a competent engineer must be able to design a structure using traditional and innovative materials. Cross Laminated Timber is a relatively new building material that is quickly gaining popularity in the construction industry. As a lightweight, carbon neutral material with strength properties matching concrete; it is an ideal alternative that may soon dominate the market. This report will document our attempt to design two identical multistorey structures using Cross Laminated Timber for the former and standard concrete for the latter. CLT resources currently include the Canadian handbook provided by FPInnovations, the North-American handbook, European codes, Canadian codes such as CSA086-09 and research papers such as Blaβ, H.J. & T. Uibel 2007. The serviceability and cost analysis of both the CLT and concrete structures have been performed using a variety of resources and engineering software; mainly ETABS . In order to validate the results, calculations have also been performed by hand.

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1.2 Objective The main objective of this report is to display competency as engineers by designing two high rise structures from different materials. The materials used will be concrete and Cross Laminated Timber (CLT); CLT is a relatively new material and as such, no Australian Standards exist for it. The second objective will be to study high rise design and CLT using eurocodes, the Canadian handbook and various research papers; knowledge obtained will allow us to design high rise structures as well as CLT structures that comply with Australian standards. Canadian and European resources have a much wider scope, providing detailed calculations and conditions for high rise and construction and CLT design. Most structural formulae are constant regardless of country, with key differences being in the modification factors and assumptions. Additionally, the CLT calculations may need to be adjusted to comply with the timber grades and characteristics available in Australia. Finally, both a structural and cost analysis of the structures will be undertaken in order to verify the stability of the structures and determine which material is more cost effective. Properties of the concrete structure and CLT structure will be entered into a variety of engineering software to determine the loads and whether or not the structure fails. Calculations will also be done by hand in order to verify the results obtained by the software. A cost analysis will determine which material is more cost effective to build with; considerations will be made for time, cost, environmental impact, work force size and ease of assembly.

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1.3 Scope Numerous factors must be considered when designing a high rise structure from any material. Most of these considerations can be categorised as either structural or economic; structural factors include loads acting on individual members such as selfweight, forces acting on the structure such as lateral/ wind load, force distribution, effect of loading of upper floors on lower floors, the purpose and design of shear walls, how members interact, etc. Additionally, economic considerations include feasibility such as cost of materials, environmental impact, time requirements such as delivery and assembly, etc. In order to deal with the dead load of individual members, the clearest method would be to create spreadsheets for each member type such as columns, slabs, walls, CLT panels etc. Engineering software such as Microstran can be used to verify results. Lateral wind load can be calculated with ease using the Australian standards, this value can then be entered into ETABS for a bending moment and shear force diagram on every member. Force distribution and effects of upper floors on lower floors can be calculated and displayed using ETABS models. The shear walls design and effect are another matter; they require in depth research in Australian standards, European and American codes. Shear walls are a crucial element of structural design; they resist the seismic and lateral forces on a structure, transferring them to the shear core. CLT members usually consist of panels of 3, 5 or 7 layers with properties determined by the timber and connections used. Once the timber grade and sizing are selected, the member can be defined on ETABS and structural analysis can be displayed. A cost analysis will be left until the end of the report. Once the materials and spans for the most effective concrete and CLT structures have been defined; their cost and quantities will be calculated and compared. Finally, an analysis of the environmental impact, time requirements, etc. will be run to determine the most economic material. Ideally, completion of our capstone will demonstrate project management, structural analysis, team work and other engineering skills and competencies.

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1.4 Overview of report The material presented in this report is organised into seven chapters; each chapter provides a different aspect of the objective, building on previous information. Chapter 1 of the report introduces the assignment and the group members; objectives, scope and group breakdown are presented to allow readers to understand the focus of the report and the group members. Chapter 2 presents background information on concrete to help any readers with no engineering background. Chapter 3 provides an introduction and background information on Cross Laminated Timber; as a new material there is limited awareness of it and new research is released each month. Chapter 4 describes the loading acting on each high rise, while chapter 5 presents the structural analysis and serviceability of the structures using a variety of engineering software. ETABS and SAFE are some of the software used to model the high rises as they are easily accessible and have a variety of functions. Chapter 6 verifies the calculations and results of the previous chapter by displaying manual calculations for both the CLT and concrete High rises. Finally, chapter 7 presents a financial analysis of both materials and the construction process. The conclusion, references and appendices are all included after chapter 7; appendices include input and outputs from the engineering software. Tables and figures have been included throughout the report to facilitate understanding of the explanations and calculations.

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1.5 Group breakdown The group includes three members completing different sub majors in the bachelor of engineering degree. Throughout the duration of the capstone assignment, roles and duties were traded and shared depending on the size of the tasks and personal circumstances. The main roles distinguished during the project have been listed below along with profiles of each team member: Mootassem Hassoun BE Civil Role: Team leader, Structural engineer, Chief researcher Mootassem Hassoun is a structural engineering student in the final semester of his bachelor degree. He has previously attained a year of engineering experience working for ACM as well as CBS consultants. Aiming to complete a practical engineering project combining the majority of materials learnt in university; he has taken the initiative to lead the group in the design as well as analysis of a CLT and Concrete high rise design. He is graduating with first class honours. Osman EL-zohbi BE Dip Eng Prac Civil (construction) Role: Project manager, CLT manager, Wind loading engineer Osman El-zohbi is a construction engineering student in the final year of his bachelor degree. He has currently attained 16 months of engineering experience working on constructions sites. With the aim of entering the engineering industry able to design and build with environmentally friendly materials; he has taken the roll of CLT and Project manager.

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Omar EL-hawat BE Dip Eng Prac Civil (Structural) Role: Concrete manager, Structural modeller, financial analyser Omar El-hawat is a structural engineering student in the final year of his bachelor degree. He has previously attained six months of onsite engineering experience and is currently interning at Ryde council. Aiming to enter the engineering industry as an experienced structural engineer; he has taken the role of Concrete manager and financial analyst.

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1.6 Restraints The main restraints encountered during the course of the capstone project included but were not limited to time restraints, lack of resources, knowledge gaps, internship priorities, etc. All members of the team are in their final year of the degree and thus, there were conflicts as each of us needed to find an internship to satisfy the Engineering practice requirements while balancing multiple subjects and the capstone. The result of this was certain group members would need time extensions for submission of components and would occasionally need to swap tasks. As will be mentioned multiple times in this report, CLT is a relatively new material and has yet to receive Australian standards. The result is, that there are few resources on the material and every month a new research paper is released describing findings and structural formulae for CLT. The main resources such as the handbook did not provide sufficient detail to understand the logic and principles used when designing with CLT. As time passed however, research papers reached their completion and were released online while references lead to more research papers with adequate explanations. As students with little variety in our industry experience we were lacking knowledge about certain aspects of engineering design. Core concepts such as shear walls and diaphragms as well as high rise construction were not taught to us and required in depth research; European and American codes had to be consulted as well as text books from other university libraries. Research papers played a large role in the understanding of design concepts while foreign video tutorials provided the necessary explanations of using key software such as ETABS and CSI columns. Engineering experience and work commitments had a large impact on our capstones; the internships took priority and exhausted us physically and mentally. Despite this, we persevered with all but one of us coming to university to work on the project every day after work.

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1.7 Reflections 1.7.1 Contribution Initially, I intended to design a simple high rise from

Written by: Mootassem Hassoun

concrete for my capstone, it seemed a practical idea that would prove my competence as an engineer. However, my supervisor mentioned it had already been done and a more original idea was needed. A compromise was reached, and my group was given the extensively larger task of designing two high rises, one form concrete and one from Cross Laminated Timber; then running a financial analysis on both. My role was team leader and structural analyst; as leader, it was my duty to keep the objective in focus and motivate my team. I strived to perform my sections of the report to the highest standards, within given time frames and be an example for my team to follow. As structural analyst and modeller I was tasked with finding a suitable software to model and structurally analyse the high rise. Most engineering software are only partially useful; aspects such as modelling may be simple to perform while structural analysis, wind loading or forces on joints may be inaccurate or not achievable. Microstran was recommended to me repeatedly, however, it is very difficult to model and analyse an entire building; walls and slabs are not available requiring improvisation and alternating between using beams and columns which result in a doubtful results. Most other software had similar problems with either not performing certain functions, not being available to students or being too complicated to use. Fortunately, after researching and trialling different software, I found the most useful software available was ETABS . This software is the most popular engineering software used worldwide, it can easily model, calculate and display all forces acting on a structure as a whole or individual members; it is also more favourable as online tutorials are available in multiple languages. After modelling and analysing the structures, I validated the results by manually calculating the forces and capacities then including them in the report. This process required extensive research in order to determine the logic behind calculations. I found there was more than one method for calculating forces on slabs, each with varying

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degrees of accuracy; the implications of this were that I had to determine which methods were used by the software and decide if the accuracy was acceptable for the purpose of the assignment. As a contribution break down mark, our team allocated the following contribution percentages that will reflect each member’s final marks: 

Mootassem Hassoun 40%



Osman El-Zohbi 30%



Omar EL Hawat 30%

1.7.2 Group Structure and references All group members participated in researching and understanding resources on concrete, CLT and high rise design. While I was responsible for performing the modelling and structural analysis of the high rises; we all researched and read all information, attempting to gain a complete understanding before I typed the manual calculations as well as software input and output. We spent several hours on the university library catalogue searching through the titles then collecting over a dozen text books for concrete construction and high rise design. Additionally, several hours were spent researching online to find suitable digital textbooks, theses as well as research papers. These digital resources provided us with crucial details as well as instructions for designing the structures. Resources collected from the library include but were not limited to ‘Reinforced Concrete The design Handbook’, ‘Worked Examples for the Design of Concrete Structures to Eurocode 2’, ‘Engineering Design in Wood’, ‘Reinforced Concrete Mechanics & Design’, etc. The library textbooks were very useful however, some concepts such as shear walls were vaguely mentioned in either them or Australian standards despite having a crucial purpose in the design of high rises. Fortunately, reading through research papers and a variety of textbooks with my group members provided enough detail to design them. Particularly useful were the thesis and research papers available online; Alshorafa, M. (2008) provided extensive detail on foundation design, while Egmond, S. (2011) supplied a beneficial thesis on medium rise timber structure design. Further sources of

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information were AKis, T. (2004) on shear walls, Blaβ & Uibel (2013) on CLT as well as connections, various papers by Doh & Fragomeni, etc. Researching and reading of resources was done together with the only separate task being the typing of the report.

1.7.3 Management Structure The structure of the group was simple; I acted as the leader and structural analyser as well as modeller and researcher. I had to keep the team motivated and directed toward the assignment objective, as well as perform the structural analysis and research concepts that we were not sufficiently familiar with. The concepts such as shear walls and isolation joints were not taught in class and were crucial to the design of the high rises; once we had understood them sufficiently, I could implement them into the high rise models. Using ETABS as well as other software, I modelled the structure and the forces acting on it; ETABS proved to be most capable software calculating and displaying forces on the structure as a whole as well as individual members. Tutorial videos were available in several languages to ensure proper use of the software’s features and capabilities. Manual calculations were performed to validate results and often lead to learning and understanding concepts and inbuilt features of the software. Omar was in charge of the financial analysis as well as the concrete and construction aspects; his duty was to gather as much information on concrete design as well as run the final comparison between the two structures. Vast amounts of information is available on concrete; he was tasked with filtering through it and compiling a condensed report on concrete for readers. A financial analysis required acquiring costs and quantities of both materials; the structures had to be compared in terms of material cost, construction time, environmental impact, durability, etc. He provided a side by side comparison detailing the construction process and costs at each stage for both materials. Osman was in charge of CLT research, wind loading and project management. He provided the calculations for the wind loading on the structure so the required capacity of the core and shear walls could be determined. Wind loading on structures depends on many factors including structure height, shape, openings, geographic location and

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cladding. Using several wind loading handbooks and enforcing decisions regarding the structural and geographic characteristics allowed for the wind speed and loading to be calculated. Information on CLT is mostly superficial unless an individual knows what to look for. After relevant information was found it had to be compiled so a reader would understand the material. Additionally, time had to be managed to ensure we could complete the capstone without falling behind in university studies or work. Using project management tools such as responsibility matrix, time budget and scope statement helped to ensure we all had our priorities organised and knew how long we had to meet milestones.

1.7.4 Technical challenge The greatest technical challenge came in the form of structural analysis; concepts and computer modelling. While attempting to design the structures, I realised that, to have structural stability I needed to use shear walls and raft slabs. Both concepts were new to me and their explanations in Australian standards as well as prescribed textbooks were not sufficient to design with. I was able to solve this issue by searching through multiple library books, and reading several online thesis papers with my group. The information provided allowed me to understand the purpose and design parameters of shear walls, raft slabs, and other concepts; shear walls enforce lateral stability by resist wind loading while ground slabs act as foundation for the structure. Once I understood this I was able to design the individual aspects of the high rises and adjust them according to the loadings. Once a suitable software was selected and acquired, I had to familiarise myself with the features and functions so I could add all inputs for an accurate output. ETABS was selected for its general accessibility and applicability; unlike most software it could model a complex structure and use Australian standards in its calculations. Learning to use ETABS was simplified by the existence of online tutorials. Tutorials exist in English, Arabic, Hindi, etc. Being fluent in both English and Arabic allowed me to watch more tutorials and broaden my scope of understanding. The result was that I became capable of modelling and structurally analysing a building, including components such as shear walls and raft slabs using ETABS and SAFE.

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1.7.5 Management challenge The greatest management challenge came in the form of prioritising and time; all three group members were simultaneously working and studying full time while working on the capstone. Additionally, I was engaged then married during the second half of our capstone. The result of this was all group members were extremely strained for time; working full time exhausted us physically and mentally. Combined with studying full time during both semesters, we had to frequently stop working on our capstone to complete other course requirements. Fortunately, we were able to persevere through all this; the entire group made an effort to come to university every day during semester and break, regardless of whether we had work or not. Staying at university until 9 pm every night became the norm. The capstone lab provided us with a silent study area and we worked consistently throughout the year. Following the milestones table and responsibility matrix, we were aware of our requirements and how much time we had to complete our sections. As a group, we had to assess the difficulty of the various assignments and quizzes in order to leave enough time for us to study/ work on them. All other time was spent working on the capstone. Other management challenges included the trading of duties and responsibilities of the capstone. Fortunately this happened while still in the research phase and did not have any impact on the assignment.

1.7.6 Group work lessons In order to complete any task with a group, certain guidelines and duties need to be established; flexibility is important but it must not interfere with team calibration. Group working tools include a prepared schedule with set milestones, time tables, regular meetings, constant monitoring and encouragement of group members, consultation of supervisors when necessary, as well as software and language diversity- many ETABS tutorials and thesis papers are unavailable in English. While working on the capstone, all group members worked better with defined responsibilities and set completion dates. Allowing too much freedom and self-

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management leads to inaccurate estimations of time needed and results in incomplete or low quality work. All group members met up at university, researched and read over the materials together; the only separate tasks were obviously the typing and calculations. In order to ensure a proper understanding of concepts; rather than using factors and formulae blindly, I researched the foundations and basic principles of calculations along with the rest of the group. Another important lesson we learnt while working as a team is to not take more work than you can handle. Initially, we planned to compare a CLT building with a prestressed building; unfortunately, we did not understand the enormity of this task and did not have enough time to complete it. Prestressed design is only taught as an elective subject with few available resources to design with sufficiently. As a result, we had to modify our capstone to compare CLT with standard concrete.

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Capstone B

1.7.7 Responsibility matrix WBS

1

Activity description

Mootassem

Osman Omar

Research capstone topic 1.1 1.2 1.3 1.4 1.5

2

Online research Interviewing past capstone students Library look up Discussion with supervisor Read student guide

R R R R R

R R R R R

R R R R R

R R R

R R R

R R R

R R R R

R R R R

R R R R

R

S R S

S

Capstone A 2.1 2.1.1 2.1.2 2.1.3 2.2 2.2.1 2.2.2 2.2.3 2.2.4 2.3 2.3.1 2.3.2 2.3.3 2.3.4 2.3.5 2.3.6 2.3.7 2.3.8 2.4 2.4.1 2.4.2 2.4.3 2.4.4 2.4.5 2.4.6 2.4.7 2.4.8 2.5 2.5.1 2.5.2 2.5.3

Appendix A Team meeting Discuss Topic Submit Appendix A Appendix B Team meeting Thorough read of Appendix B guideline Discuss marking indicator Fill Appendix B template Appendix C Introduction Objectives Methodology Time line Attach Appendix B Submit Draft to Rijun Rijun's review and signature Submission Structural analysis and design study Study prestress concrete Research CLT Study CLT design Study structural design Study loading principles Practice AutoCAD Practice structural analysis software Practice Structural design software Building model Research building plans Team meeting Approve one building model

R S R R R R

R R R R

R R R R R

R R R R R R R R

R R R R R R R R

R R R R R R R R

R R R

R R R

R R R

P a g e 15

Chapter 1: Introduction WBS 2.6 2.6.1 2.6.2 2.6.3 2.6.4 2.6.5 2.6.6 2.6.6.1 2.6.6.2 2.6.6.3 2.6.6.4 2.6.7 2.6.8 2.6.9 2.6.10 2.6.11 2.6.12 2.6.13 2.6.14

P a g e 16

Activity description Appendix D Team meeting Read Appendix D guideline Scope statement Prepare WBS Status report Progress report Overview Project achievements Current project activities Project challenges Budget Responsibility matrix Risk analysis Quality Progress assessment form Team review Rijun's review and signature Submission

Capstone B

Mootassem

Osman

Omar

R R

R R R S R R

R R S

R R R S R

R

R R S R

S R R R R

R R R R R

R R R S S S S R S R R R R

Chapter 1: Introduction WBS

3


Capstone B Mootassem

Osman

Omar

R

R

R

R R R R R R

R R R R

R R R R R S

R R R R

S S R R

Capstone B 3.1

3.2 3.3 3.4 3.5 3.5.1 3.5.1.1 3.5.1.2 3.5.1.3 3.5.2 3.5.3 3.5.3.1 3.5.3.2 3.5.3.3 3.5.4 3.5.5 3.5.6 3.5.7 3.6 3.6.1 3.6.2 3.6.3

Revised Proposal Capstone proposal assessment form Appendix B and updated EHS D/HD abstract Final Report Concrete research Structural modelling Draw Building model using AutoCAD Record structural data Wind load calculation CLT research Model building in structural design software Analyse the software output CLT hand design calculations Structural comparison between the two approaches Financial comparison between the two approaches Quality review Printing and submission Presentation Team meeting PowerPoint slides Practice presentation

R R R

S

S

S S S

S

R R

R R

S R R

R R R

R R R

R R R

R

P a g e 17


Capstone B

1.7.8 Time Budget WBS


Decided (hours)

Actual (hours)

Varianc e%

Research capstone topic

1 1.1

330

300

9.09

1.2

Online research Interviewing past capstone students

21

21

0

1.3

Library look up

9

14

-55.56

1.4

Discussion with supervisor

18

15

16.67

1.5

Read student guide

12

9

25

2

UNDERBUDGET METBUDGET OVERBUDGET UNDERBUDGET UNDERBUDGET

Capstone A

2.1

Appendix A

2.1.1

Team meeting

18

18

0

2.1.2

Discuss Topic

18

18

0

2.1.3 2.2

Submit Appendix A Appendix B

3

3

0

2.2.1

Status

18

18

0

2.2.2

Team meeting Thorough read of Appendix B guideline

18

18

0

2.2.3

Discuss marking indicator

1

1

0

2.2.4

Fill Appendix B template

1

1

0

P a g e 18

METBUDGET METBUDGET METBUDGET METBUDGET METBUDGET METBUDGET METBUDGET


Capstone B

Decided (hours)

Actual (hours)

Variance %

2.3

Activity description Appendix C

2.3.1

Introduction

3

2

33.33

2.3.2

Objectives

4

5

-25

2.3.3

Methodology

8

6

25

2.3.4

Time line

6

8

-33.33

2.3.5 Attach Appendix B Submit Draft to 2.3.6 Rijun Rijun's review and 2.3.7 signature

1

1

0

1

1

0

1

1

0

2.3.8

WBS

Submission Structural analysis 2.4 and design study Study prestress 2.4.1 concrete

1

1

0

240

230

4.17

2.4.2

Research CLT

220

220

0

2.4.3

Study CLT design Study structural design Study loading principles

220

230

-4.55

180

180

0

180

200

-11.11

60

42

30

72

60

16.67

72

72

0

2.4.4 2.4.5 2.4.6

Practice AutoCAD Practice structural 2.4.7 analysis software Practice Structural 2.4.8 design software

Status UNDERBUDGET OVERBUDGET UNDERBUDGET OVERBUDGET METBUDGET METBUDGET METBUDGET METBUDGET

UNDERBUDGET METBUDGET OVERBUDGET METBUDGET OVERBUDGET UNDERBUDGET UNDERBUDGET METBUDGET

P a g e 19


WBS

3 3.1


Decided (hours)

Capstone B

Actual (hours)

Variance %

Status

Capstone B UNDERBUDGET METBUDGET METBUDGET METBUDGET OVERBUDGET UNDERBUDGET OVERBUDGET METBUDGET UNDERBUDGET UNDERBUDGET OVERBUDGET

6

4

33.33

2

2

0

3.3

Revised Proposal Capstone proposal assessment form Appendix B and updated EHS

2

2

0

3.4

D/HD abstract

8

8

0

3.5

Final Report

407

373

9.09

3.5.1 Concrete research 3.5.1. 1 Structural modelling 3.5.1. Draw Building model 2 using AutoCAD 3.5.1. Record structural 3 data Wind load 3.5.2 calculation

45

40

11.11

50

52

-4

20

20

0

10

9

10

20

18

10

3.5.3

CLT research Model building in structural design software Analyse the software output CLT hand design calculations Structural comparison between the two approaches Financial comparison between the two approaches

45

50

-11.11

36

28

22.22

35

28

20

50

50

0

UNDERBUDGET UNDERBUDGET METBUDGET

5

UNDERBUDGET

40

34

15

Quality review Printing and submission

10

10

0

6

24

-300

3.2

3.5.3. 1 3.5.3. 2 3.5.3. 3

3.5.4

3.5.5 3.5.6 3.5.7

P a g e 20

40

38

UNDERBUDGET METBUDGET OVERBUDGET

Chapter 1: Introduction 3.6 3.6.1 3.6.2 3.6.3

Presentation Team meeting PowerPoint slides Practice presentation

Capstone B

18 12

-

-

N/A N/A

3

-

-

N/A

1.7.9 Milestones Milestone ID

1

Major Deliverable

Due Date

Status

19/06/2015 19/06/2015 19/06/2015 6/03/2015 19/06/2015

Completed Completed Completed Completed Completed

6/03/2015 20/03/2015 20/03/2015 19/06/2015 19/06/2015 19/06/2015

Completed Completed Completed Completed Completed Completed

21/08/2015 21/08/2015 21/08/2015 23/10/2015 20/11/2015 26/11/2015

Completed Completed Completed Completed Scheduled Scheduled

Research capstone topic 1.1 1.2 1.3 1.4 1.5

2

Online research Interviewing past capstone students Library look up Discussion with supervisor Read student guide

Capstone A 2.1 2.2 2.3 2.4 2.5 2.6

3

Appendix A Appendix B Appendix C Structural analysis and design study Building model Appendix D

Capstone B 3.1 3.2 3.3 3.4 3.5 3.6

Revised Proposal Capstone proposal assessment form Appendix B and updated EHS D/HD abstract Final Report Presentation

P a g e 21

P a g e 22

Chapter 2: Concrete Design

P a g e 23

Chapter 2: Concrete design 2.1 Material Technology and Loading

Capstone B Researched by: Omar El Hawat Written by: Omar El Hawat

2.1.1 Concrete Materials Concrete is a building material that is composed primarily of fine and coarse aggregates, cement and Water. When water is added to the mixture it creates a chemical reaction with the cement which binds the aggregates together into one mass when hardened. The mass of the concrete is made up of both fine and coarse aggregates. The proportion of the mixtures as well as external factors of placement will often determine the strength and durability of the concrete.

2.1.2 Cement and Water In order for the concrete to harden, an exothermic chemical reaction called Hydration occurs between the water and cement. This process will bond the aggregates and the fresh concrete together into one mass. Once the concrete hardens, it will continue to gain strength over the period of its lifetime. The cement that is most commonly used in concrete is Portland cement which contrails calcium oxide, aluminium oxide and silicon oxide. The water to cement ration is often designed as this will affect the strength, durability and workability of the concrete. The water to cement ratio is often kept at 0.35-0.4 for complete Hydration. The Higher the water to cement ration is, it will increase the workability of the concrete and make it easier to place especially in tight places with heavy reinforcement. However with a lower the water to cement ratio, the strength and durability of the concrete is increased. The figure 2.1 shows the relationship of water to cement ratio and how it affects the concretes strength.

P a g e 24

Chapter 2: Concrete design

Capstone B

Figure 2.1: water cement ratio configuration chart (Omfra 2009)

2.1.3 Aggregates Aggregates take up a large portion of the concrete which is typically somewhere between 70-75% of the volume of concrete. Aggregates are classified into two categories, Fine and Coarse aggregates. Fine aggregates consist mainly of sand with a maximum particle size of 2mm diameter and anything smaller such as clay and silt particles. Coarse aggregates are considered to be larger than 2mm and can vary up to a maximum size of 60mm in diameter. The sizes of various aggregates are shown below: Clay = 40 MPa

However in the Australian standards AS3600, the values for the Elastic modulus of concrete ‘Ec’ can be found in relation to the f’c and fcmi and are the values used by designers in their calculations. The density of concrete for the purpose of design is also

taken

to

be

2400kg/m3.

Table 2.1: Mechanical properties of concrete (AS3600-2009)

2.1.6 Reinforcement Steel Concrete has a relatively low tensile strength and undertakes brittle failure which makes it undesirable for use in structures. The Steel bars are normally placed on the tensile face of the reinforced concrete to carry reinforced loads, however, at times can be used to carry compressive loads to prevent a brittle failure being stopping concrete from crushing. Tensile steel bars not only give concrete tensile strength but also give it ductility. The values of the properties of steel used in design calculations are used from the idealised stress-strain curve with typical yield strength of 500MPa and a yield strain of 0.0025mm. The figure below shows the stress-strain diagram for steel and illustrates that the yielding starts two third of its ultimate strength. However, the graph on the right shows the idealised stress strain curve where the graph initially yields to be the failing stress and strain. This itself will factor any discontinuities and considers any strength factors in the design.

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Capstone B

Figure 2.4: Concrete stress vs strain (Google 2014)

2.2 General Design Requirements

Researched by: Mootassem Hassoun

All structures must be designed to be safe during


their expected life and to fulfil their expected use through meeting serviceability requirements. In Australia there are more than one building regulation that governs the design and gives detailed design requirements to provide protection to the structure owners, occupants and the general public. AS3600-2009 is the design standards for concrete structures. The standards provide guidelines and deemed to control for strength, serviceability, robustness and fire design. This paper is consistent with the most recent Australian standards requirements. The guidelines in AS3600-2009 refer to what is called the limit state philosophy of structural behaviour. Under the limits state philosophy umbrella, the strength design is governed by ultimate limit state requirement that are placed to prevent structural failure. Moreover, serviceability are related to the serviceability limit states related with the failure of the structure to perform its intended function throughout its life.

2.2.1 Ultimate Limit State (ULS) Strength limit state is the design to prevent variable structural failure modes. AS36002009 list various failure modes that must be designed against (including compression failure, shear failure, tension failure, torsional failure, bending failure, etc.). In addition to listing the failure modes, the standards provide calculation procedures to assess the structure’s capacity to withstand against failure.

P a g e 29


Capstone B

The ultimate strength capacity Ru calculation procedures are given in AS3600-2009 based on the characteristic values of the material strength. Moreover, Ru is reduced using a probability factor ϕ (capacity reduction factor). On the other hand, to ensure a satisfactory performance, the design capacity must be reached only in extreme loading conditions. Based on this philosophy, the design capacity should be calculated to withstand a much larger load than what is found in normal conditions.

Stress resultant Value of φ Pure bending (for ductile members) 0.8 Pure axial compression 0.6 Pure axial tension 0.8 Shear 0.7 Torsion 0.7 Bearing 0.6 Table 2.2: Values of ф for strength design using elastic analysis The reduction factor ϕ varies in AS3600 to reflect the different levels of uncertainties in calculating the design capacity Rd. ϕ also depends on the nature or probability of failure.AS3600 states that the design capacity value фRd should be equal or bigger than the design action effects Ed, where the design action effects are given by a combination of various types of loadings that might be applied on the structure in the same time. In general there are two classifications of any failure mode. First type is known as the ductile mode of failure. This type is the most preferable as it allows the steel to yield, deflect significantly and giving major warning of failures before the concrete crushes and the onset of failure occurs. Whereas the second type, known as brittle failure is the result of having an over-reinforced section, leading the concrete to fail in brittle manner before the reinforcement yielding. This type of failure is highly undesirable as it happens suddenly without any warning signs. Based on the above discussion of failure modes, ϕ factor must also reflect such philosophy. Therefore, ϕ is equal to 0.8 for ductile failure and 0.6 for brittle failures as brittle failures are not predictable.

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Capstone B

2.2.2 Serviceability Limit Serviceability includes design for deflection limits, vibration and cracking. The loads assessed in serviceability design is normal loading on the structure. Serviceability loads and combinations are given in AS/NZ 1170. Design for fire resistance guidelines are found in the National Construction Code and AS3600. The limitations are in the form of fire resistance periods that the structure must deemed to comply with.

2.3 Reinforced Concrete Beams

Researched by: Omar El Hawat Written by: Omar El Hawat

Beams are structural elements used in design to withstand transverse loading through resisting any bending action. In order to find the right dimensions and sizing of the beam, they need to be designed in order to withstand the necessary applied forces.

2.3.1 Ultimate Strength Theory The ultimate strength of the member is reached when a large enough load is applied to the member and causes it to fail. Structural engineers need to ensure that the member will not fail under working load conditions. In order to do this, the stress-strain analysis of the materials both concrete and steel need to be closely analysed. From the analysis, the ultimate strength and capacity of the member can be calculated. When assessing the Ultimate strength there are four main assumptions that need to be considered: I.

Plane sections remain plane: Plain sections that are normal to the beams axis remain plane after bending and twisting has occurred. The strain in concrete members are linear.

II.

The stress-strain for steel is bilinear: Reaches a maximum yielding stress of 500MPa and strain approaches infinity.

III.

The stress-strain curve of concrete to its failure point is non-linear: Concrete fails at a strain of 0.003.

IV.

Concrete tensile strength is ignored.

P a g e 31


Capstone B

Different loading stages on a beam will depict different stress distributions over the cross sections. For a load that will cause no cracking to the member will depict a stress distribution as shown in (a) of the figure below. This is because concrete has not cracked and carry a tensile load as the member is bending. Stress distribution can be assumed linear in this phase. After the member has cracked the member will continue to carry compressive loads however will no longer carry any tensile load. All the tensile loads that are induced on the section will be carried by the steel reinforcement of the concrete member. The stress distribution for the concrete still remains linear as seen in the figure (b) It is when the member has reached its ultimate state that is when the stress distribution becomes non-linear and looks similar to that in the figure (c). As the load increases the depth to the neutral axis of the member decreases because the concrete cracks become deeper.

Figure 2.5: Concrete stress Block in beams (Chowdhury & Loo 2010)

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Capstone B

The ultimate moment of the cross-section of the members can be calculated using the following formula: 𝑀𝑢 = 𝑇. 𝑍 = 𝐶𝑢𝑙𝑡. 𝑍 Mu= Ultimate Moment of the section T= Tensile Force Cult=Compressive Force at ultimate state The compressive forces (Cult) is computed by calculating the volume of the stress blocks shown in the figure 2.6. The stress distribution block for the section that is at its ultimate capacity is difficult and complex to calculate and requires complex mathematics which make it inconvenient for designers. The actual shape of the stress distribution depends on many factors and varies from different concrete types. However, an equivalent stress block has been developed and been widely accepted by many around the world. The equivalent stress block will give the same value for Mu which is the ultimate moment capacity for the actual stress curve. Figure 2.6 below shows the exact curve of the stress block and the equivalent stress block.

Figure 2.6: Reinforced concrete internal forces, strain diagram and stress diagram (UTS lecture notes)

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Capstone B

In the Australian standards (AS3600), it can be found that the factors can be calculated by: 𝛼2 = 1.0 − 0.003 𝑓 ′ 𝑐

𝑊ℎ𝑒𝑟𝑒 0.67 ≤ 𝛼2 ≤ 0.85

And 𝛾 = 1.05 − 0.007 𝑓 ′ 𝑐

𝑊ℎ𝑒𝑟𝑒 0.67 ≤ 𝛾 ≤ 0.85

2.3.2 Ultimate Strength of a Single Reinforced Rectangular Section Concrete failure can occur in several forms such as concrete breaking due to excessive compression causing the concrete to give a sudden failure with no warning. Such beams are considered to be over reinforced beams. When this happens the concrete would have reached a strain ε = 0.003. Concrete can also fail due to an excessive tensile load. This happens when the steel yields and the strain exceeds the yielding strain of ε = 0.0025. When a member fails due to its tensile strength being exceeded, then it is considered to be an under reinforced beam that gives a gradual ductile failure.

2.3.2.1 Balanced Failure A balanced failure occurs when the Steel strain has reached ε = 0.0025 and concrete strain has reached ε = 0.003. The probability of this failure to occur is minimal however it is important to analyse its mode of failure in flexural design of members in order to ensure that tensile failure will occur as the mode of failure. Figure 2.7 below shows the different modes of failures and their corresponding strain diagrams.

Figure 2.7: Strain distributions at the ultimate state (Chowdhury & Loo 2010)

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Capstone B

By analysing the balanced failure, it is easy to find the neutral axis as a consequent. This will give the designer an indication on how to design the cross-section of the beam and to control how it fails. The neutral axis of a section is determined by the formula, N.A = ku.d. By referring to Figure 2.7, the following can be derived: 𝑘𝑢𝑏 . 𝑑 𝑑 = 𝜀𝑐𝑢 𝜀𝑐𝑢 + 𝜀𝑠𝑦 𝑘𝑢𝑏 =

𝑘𝑢𝑏 =

𝜀𝑐𝑢 𝜀𝑐𝑢 + 𝜀𝑠𝑦 0.003

𝑓𝑠𝑦 0.003 + 200000

𝑘𝑢𝑏 =

600 600 + 𝑓𝑠𝑦

if 𝑓𝑠𝑦 = 500 MPa, then kub = 0.545 Hence to ensure that balanced failure does not occur and that a tensile failure will take place, the value of ku must be less than 0.545. However, the Australian standard AS3600 recommends that kuo should be less or equal to 0.36, where the neutral axis is taken with respect to the distance to the outer level of tensile steel. If this value is exceeded then compressive steel is required to be added.

2.3.3 Allowable Steel in Beam Section The resultant forces in the stress distribution of a section that undergoes a balanced failure are: 𝐶 = 𝛼2 . 𝑓 ′ 𝑐. 𝛾. 𝑘𝑢𝑏 . 𝑏. 𝑑 𝑇 = 𝐴𝑠𝑡 . 𝑓𝑠𝑦 = 𝑝𝑏. 𝑑. 𝑏. 𝑓𝑠𝑦 Due to Equilibrium, ∑Fx = 0 and hence C=T 𝛼2 . 𝑓 ′ 𝑐. 𝛾. 𝑘𝑢𝑏. 𝑏. 𝑑 = 𝑝𝑏. 𝑑. 𝑏. 𝑓𝑠𝑦

P a g e 35


Capstone B

Hence: 𝑝𝑏 =

𝛼2 . 𝑓 ′ 𝑐. 𝛾. 𝑘𝑢𝑏 𝑓𝑠𝑦

If the steel ratio of the section is 𝑝 < 𝑝𝑏 the member is then considered to be under reinforced however if the steel ratio is > 𝑝𝑏 . In the AS3600 concrete standards the maximum allowable steel that can be in a beam section can be calculated as: 𝑝𝑎𝑙𝑙 = 0.4 . 𝛼2 . 𝛾.

𝑓 ′ 𝑐. 𝑓𝑠𝑦

This Value is not to be exceeded unless there is steel reinforcement that will be carrying compressive loads.

2.3.4 Moment Capacity Equation The stress and strain diagrams of the cross section of a single reinforced beam can be represented in the figure below:

Figure 2.8: Stress and strain diagrams of singly reinforced beams (Chowdhury & Loo 2010) The sum of the compressive and tensile forces are: 𝐶 = 𝛼2 . 𝑓 ′ 𝑐. 𝛾. 𝑘𝑢. 𝑏. 𝑑 𝑇 = 𝐴𝑠𝑡 . 𝑓𝑠𝑦 Due to Equilibrium, ∑Fx = 0 and hence C=T hence the value of ku can be determined as: 𝐴𝑠𝑡 .𝑓𝑠𝑦

Ku = 𝛼2 .𝛾.𝑓′ 𝑐.𝑏.𝑑

P a g e 36

or

𝑝𝑡.𝑓𝑠𝑦

Ku = 𝛼2 .𝛾.𝑓′ 𝑐


Capstone B

Hence the Moment capacity of the section can be determined by taking moments from the level of compressive force where the moment is taken to be a value of 0. ∑M = 0 at level of C 𝑀𝑢 = 𝐴𝑠𝑡 . 𝑓𝑠𝑦 . 𝑑 [ 1 −

𝛾. 𝑘𝑢 ] 2

The value of Mu can also be taken as the following when subbing the equation of ku in the formula 𝑀𝑢 = 𝐴𝑠𝑡 . 𝑓𝑠𝑦 . 𝑑 [ 1 −

𝐴𝑠𝑡 . 𝑓𝑠𝑦 ] 2 . 𝛼2 . 𝑏. 𝑑. 𝑓′𝑐

The value of Mu can be taken as the ultimate capacity of the section. However, for design calculations there this value needs to be factored down to its effective moment capacity as show below: 𝑀′ = ∅. 𝑀𝑢 Where ∅ = 1.19 −

13 .𝑘𝑢𝑜 12

For Class N reinforcements: 0.6 ≤ ∅ ≤ 0.8 For Class L Reinforcements: 0.6 ≤ ∅ ≤ 0.64

2.3.5 Double Reinforced Rectangular Sections For single reinforced sections in the tensile region of the concrete member, the increase of steel reinforcement will not increase the moment capacity of the section however it will increase its tensile strength which will hence result in compressive failure when over loaded. Nevertheless, in some cases compressive steel is added into the concrete beam which will help carry compressive loads and hence increase the strength of the beam. Compressive steel is also useful for reducing shrinkage and creep associated in beams. Figure 2.9 below shows the stress and strain distributions of a typical section of a double reinforced beam.

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Capstone B

Figure 2.9: Stress and strain distributions of a doubly reinforced beams. (UTS lecture notes) When analysing a section with steel reinforcement in both compression and tension region of the section there are two scenarios that may occur. The first scenario is that the steel of the tensile region will yield whereas the steel in the compressive region has not yet yielded. And the other scenario is where both steel in the compressive and tensile region have both yielded.

P a g e 38

Chapter 2: Concrete design 2.4 Design of Two-Way Transfer Slabs Flat slabs are frequently referred to as two way

Capstone B Researched by: Mootassem Hassoun Written by: Mootassem Hassoun

slabs. Flat slabs as the name indicates are a concrete plate supported on columns. This type of slabs attract significant bending moments in both its orthogonal axis. Contrary to slabs supported on four sides and one way slabs, these slabs have larger moments on the longer side. When flat slabs are gradually loads, the first cracks appear near the column top. These cracks gradually extend and widen, creating an umbrella shaped like zone on top of columns. In comparison between flat slabs and slabs continuously supported on their four edges, the first one clearly examines high bending moments as it is only supported on its corners. Furthermore, the column-supported slab deflect along its span, while the interior slab not supported on the columns further exhibits higher deflection than the supported strip. Two major design aspects that governs the slab thickness are deflection and punching shear.

2.4.1 Flat slab design The regions of the slab directly on top of columns is subjected to major transfer moment and shear forces from the slab to the column beneath it. These forces generate punching shear, which could result in the column head penetrating through the slab.

Figure 2.10: Illustration of danger caused by punching shear failure (Google 2011)

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Capstone B

The model used to estimate the punching shear assumes that the forces are transferred to the column within the punching shear permitter u. The critical shear perimeter is at a distance of dom/2 from the face of the column, where dom/2 is the average effective depth of the slab around the critical perimeter. Another major contributor to punching shear is the magnitude of the moment transferred 𝑀𝑉∗ . Around the critical perimeter, part of 𝑀𝑉∗ is transferred by flexure and the remainder is transferred by torsion to the column. This moment is equal to the unbalanced moment at the top of the column obtained from the structural analysis, and at an interior support it should not be less than the following expression: 𝑀𝑉∗ = 0.06 [(1.2 qG + 0.75 qQ ) Lt (Lo)2 – 1.2qG Lt (𝐿′𝑜 )2] Where Lt is the width of the design strip. 𝐿′𝑜 is the shorter length in the adjoining spans.

Figure 2.11: critical punching shear perimeter ( AS3600:2009 )

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Capstone B

The punching shear capacity of the shear perimeter denoted as Vuo is calculated as the following: 

If 𝑀𝑉∗ = 0, Vuo = u dom fcv

And fcv = 0.17 (1 + 2/βh) √𝑓𝑐′ ≤ 0.34 √𝑓𝑐′ Where βh is the ratio of the longest dimensions of the column to the short direction. 

If 𝑀𝑉∗ ≠ 0, Vu = Vuo / (1+ ( (𝑀𝑉∗ /𝑎)/ (( 8 𝑉 ∗ dom)/u))

Where a is the width of the column in the direction of the span plus dom. 

If ϕVu < V*, then either increase the depth of the slab or use special reinforcement (shear studs)

Where V* for any column is the product of the factored design floor load and its tributary area. Shear studs calculation: There are no information about shear studs in AS3600, therefore the following calculations come from the research of Lim and Rangan. The shear capacity with shear studs is as the following: In slab strip -

Vu = min ( Vuo (1 + Ks), Vuo/ ((1/Ks)+(u x 𝑀𝑉∗ /(8V* ad))))

Where Ks = Avsfvydu / ( Vuo x s x b) Where Avs = cross sectional area of row of studs in the slab strip fvy = 500 MPa (yield strength of the studs) s = spacing of the studs b = width of the critical shear perimeter perpendicular to the direction 𝑀𝑉∗ For torsion strip -

Vu = min (Vuo (1 + Ks), Vuo/ ((1/(1+Kt))+(u x 𝑀𝑉∗ /(8V* ad))))

Where Kt = Avtfvydu / ( Vuo x s x a) Where Avs = cross sectional area of row of studs in the torsion strip

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fvy = 500 Mpa (yield strength of the studs) s = spacing of the studs a = width of the critical shear perimeter parallel to the direction 𝑀𝑉∗ Minimum cross sectional area of stud reinforcement Avs ≥ (0.35bs/fvy) Avt ≥ (0.35as/fvy)

Figure 2.12: Illustration of parameters b and a (Lim &Rangan 2015)

Figure 2.13: Illustration shear studs layout. (Lim &Rangan 2015)

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Figure 2.14: shear studs placement in practice (Google 2015)

2.4.2 Slab Analysis Flat slabs behaviour is much more complex to model and analyse compared to the usual two-way slabs. Therefore, any model or method used to analyse the flat slab system will be conservative in its values and if any two methods used to compare the results it will be seen that great difference in values is apparent. There are three different ways to analyse a flat slab system namely: Direct design method, Equivalent frame method and Finite Element method. The first and last method will be discussed in elaborated details in the section below and chapter 5. However, only flat plates without perimeter beams are covered.

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2.4.2.1 Direct Design Method This is known as the simplified method in AS3600. The method is describing the load path between the slab and the supporting structure beneath it. The method is based on the lower bound method of plasticity, therefore, equilibrium must be achieved and ductility must be present for the designer to achieve the load path sought. Each direction is considered individually, starting with y-direction first as it has the largest moment value. To calculate the moment in a specific direction, the entire slab is divided into strips bound by the column centre line. Similar to beams, the negative moment will be on top of the columns and the positive

Figure 2.15: Width of design strips. (AS3600-2009) moment will be in the mid-span. Each of these moments are further divided within the strip into a column strip and a middle strip as shown in the figure below. The direct design method only implies when the following conditions are present: 

The slab should include minimum two spans in each direction;



The supporting grid in any design strip must be aligned with a tolerance of each individual support be offset by a maximum of 10% from the centreline of the strip;

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Chapter 2: Concrete design 

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In any design strip, the ratio of any long span to short span must be less than two;



In any design strip, the adjacent spans must not differ by one-third and in any case the end-span must not be longer than the adjacent interior span;



All lateral forces on the structure must be resisted solely by the shear-walls or braced frames;



Vertical loads are uniformly distributed;



The live load is not twice bigger than dead load.

The total static moment to be distributed is Mo = q* Lt 𝐿20 / 8. Using the simplified method approach, the static moment is distributed between positive and negative spans. The direct design method relies on fixed moment factors that depends on the type of spans used. The following tables are extracted from AS3600-2009 and are used in the analysis as it will be illustrated in this section: Positive Types of slab system and Exterior negative moment

Interior

edge rotation restraint

negative

moment factor

factor

moment factor

0.25

0.5

0.75

Flat slabs with exterior edge

restrained

columns only

by

Table 2.3: Design moment factors for an end-span. ( AS3600-2009 ) Type of slab system All types

Negative momnet Positive moment factor factor 0.65 0.35

Table 2.4: Design moment factors for an interior span. ( AS3600-2009 )

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The moment distribution factors applied in the above tables are for the design strip which includes both column and middle strip. Therefore, these factors must be further distributed to the column and middle strip in the following proportions:

Bending moment under consideration Negative moment at an interior support Negative momnet at an interior support without spandrel beam Positive moment at all spans

Column strip 0.8

Middle strip 0.2

0.85

0.15

0.6

0.4

Table 2.5: Distribution of bending moment within the design strip. ( AS3600-2009 )

As a result of the above mentioned moment distribution factors. The following simplified diagram are produced to illustrate the moment diagrams in the design strip:

Figure 2.16: Middle strip distribution factors.

Figure 2.17: Column strip distribution factors.

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2.4.3 Design and Detailing of Flat Slabs

2.4.3.1 Flexural reinforcement In flat slabs, the long direction (y-direction) has the largest moment which lead to analysing this layer first. The reinforcement required to resist this moment is calculated using the following simplified formula: p = M* / (370 x d2) per linear meter Nevertheless, AS3600 provided a formula for minimum flexural reinforcement in flat slabs as the following: ′ p = 0.24 (Ds /d)2 (( 𝑓𝑐𝑡.𝑓 ) / 𝑓𝑠𝑦 )

2.4.3.2 Crack Control For structures to meet the requirements of AS3600 they must be designed for durability. Durability can be partially achieved by providing cover for fire rating and by controlling the cracks in the slab. There are two ways to restrain cracks explained in the following points: 

Cracks developed from large reinforcement bar sizes. This type is prevented by providing small bars. In practice low ductility mesh is used with N12 or N16 bars.



Cracks resulting from high stress values in reinforcement. Therefore, stress should be limited to a small values in bars.

AS3600 states that the minimum spacing between bars shall be the minimum of 2Ds or 300mm. Moreover, AS3600 is flexible in terms of shrinkage and temperature cracks as it allows the designer to choose the degree of crack control required. Minimum reinforcement for temperature and shrinkage control are as the following: In both directions of a flat slab, the area of reinforcement shall not be less than 75% of the following shrinkage areas. 1. 0.00175bDs for minor degree of cracks control; 2. 0.0035bDs for moderate degree of cracks control; or 3. 0.006bDs for moderate degree of cracks control.

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2.4.4 Deflection and Serviceability In the vicinity of AS3600 there are two ways to find the deflection of slabs. The first method is called deemed to comply and it is found to be the easiest to preform when it comes to hand calculations. This method relies on calculating the ratio of span to depth and compare this ratio with the upper limit that resemble the modified stiffness of the slab. Lef /d ≤ k3 k4 [ (Δ/Lef ) Ec / Fd.ef ]1/3 Where Ln = clear span from face of the support. Lef = effective span, min ( centre to centre long span, Ln + Ds ) Δ/Lef = deflection limit ratio, 1/250 for total deflection and 1/500 for incremental deflection. k3 = 1.05 for a flat slab k4 = 1.75 for the end span of a continuous span. 2.1 for an internal span of a continuous span. Ec = modulus of the concrete Fd.ef = the effective design load for either total or incremental deflection Total defection load (1.0 +kcs)qG + ( Ψs + kcs Ψl )qQ Incremental deflection kcsqG + ( Ψs + kcs Ψl )qQ kcs = multiplier at mid span , equal to 2-1.2 ( Ast/ Asc ) Ψs, Ψl from AS/NZS 1170.0

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The second method is more accurate and it involves calculating the actual deflection value of the slab. The effective section inertia is found using the famous Branson’s formula. One should note, that Branson’s formula was developed during testing of heavily reinforced beams, while slabs are lightly reinforced. The steps in this method are presented in points below: ′ ′ 1. Find the cracking stress σcr = 𝑓𝑐𝑡.𝑓 - σcs, where 𝑓𝑐𝑡.𝑓 = 0.6 √𝑓𝑐′ ∗ 2. σcs = [ 2.5 pw / (1+50 pw)] x Es 𝜀𝑐𝑠 ′ 3. 𝑀𝑐𝑟 = (𝑓𝑐𝑡.𝑓 - σcs ) Ig / ( yb )

4. If 𝑀𝑐𝑟 > 𝑀 ∗ use Ig for subsequent calculation, 𝑀𝑐𝑟 < 𝑀 ∗ use Icr for subsequent calculations. 5. Find Icr using mechanics of solid transferred section method or assume Icr = 0.33 Ig 6. Ief = Icr +k(Ig – Icr ) x ( Mcr /M)3 where k =1 for short time loading and for long term deflection k = 0.5. 7. Short term deflection 𝛥𝑠 = 𝐿2𝑜 x ( 𝑀𝐿.𝑠 + 10 𝑀𝑀.𝑠 + 𝑀𝑅.𝑠 ) / ( 96 Ec x Ief ) 8. Short term loading qs = qG + Ψs qQ 9. long term loading ql = qG + Ψl qQ 10. long term deflection 𝛥𝑙 = (qs / ql ) 𝛥𝑠 11. Δtot = 𝛥𝑠 + kcs 𝛥𝑙

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Chapter 2: Concrete design 2.5 Shear Walls Each structure is constantly subjected to lateral

Capstone B Researched by: Mootassem Hassoun Written by: Mootassem Hassoun

forces that displace the building causing serviceability issues. As a solution buildings generally resist lateral movements through elements called shear walls. These elements usually have high stiffness on one of their axis that help them resist lateral loading.

Shear-walls

Figure 2.18: shear wall layout in the proposed model.

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2.5.1 Types of shear walls There are three types of shear walls used in structures today. 

Short walls, if the wall is one or two storey high. The design of these walls are typically dominated by shear. They usually have an aspect ratio of H w/Lw of less than or equal to 2. Such walls would be designed using the strut and tie modelling or the provision of ACI chapter 10 and 11.



Slender shear walls, if the wall is more than three or four levels in height. This type of wall generally resist flexural action as it acts as a vertical cantilever wall rather than in shear. Such walls have an aspect ratio of Hw/Lw greater or equal to 3. These walls are typically designed with the provision of AS3600 chapter 11 and ACI chapter 10 and 11.



Shear walls with aspect ratios between 2 and 3 exhibit both flexural and shear behaviour.

Figure 2.19: shear walls types of deformation (Google 2012) Shear walls may come in a simple planar form, or they can form wall assemblies such as the ones found in building service cores or stair cases.

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Beside shear walls, there are three common structural systems to resist lateral forces. The systems are explained below: 1. Moment-resisting frames: the building is made of an interconnected grid of beams and slabs on each storey with the absence of walls. Such structure will exhibit an immense amount of lateral deflections. This type of structure will behave in a sway manner magnifying the bending moment in the frame, resulting in an oversizes members. In such cases, walls or bracing elements are used to reduce the lateral deflections. 2. Bearing-wall systems: such system is usually used in hotels or residential buildings, where bearing walls are laid out between rooms and apartments. The walls in such case will generally as a cantilevered section and undergo flexural actions. 3. Shear-wall buildings: such systems are normally found in building ranging from 8 to 30 storey in height. The lateral loads is normally shared between the shear walls and the frame of the structure. This paper will focus mainly on Shear wall building systems.

Figure 2.20: Typical shear wall-frame type configuration (Wight 2009)

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2.5.2 Architectural Aspects Most RC buildings with shear walls also have columns; these columns primarily carry gravity loads (i.e., those due to self-weight and contents of building). Shear walls provide large strength and stiffness to buildings in the direction of their orientation, which significantly reduces lateral sway of the building and thereby reduces damage to structure and its contents. Since shear walls carry large horizontal earthquake forces, the overturning effects on them are large. Thus, design of their foundations requires special attention. Shear walls should be provided along preferably both length and width. However, if they are provided along only one direction, a proper grid of beams and columns in the vertical plane (called a moment-resistant frame) must be provided along the other direction to resist strong earthquake effects. Door or window openings can be provided in shear walls, but their size must be small to ensure least interruption to force flow through walls. Moreover, openings should be symmetrically located. Special design checks are required to ensure that the net cross-sectional area of a wall at an opening is sufficient to carry the horizontal earthquake force. Shear walls in buildings must be symmetrically located in plan to reduce ill-effects of twist in buildings (Figure 2.21). They could be placed symmetrically along one or both directions in plan. Shear walls are more effective when located along exterior perimeter of the building – such a layout increases resistance of the building to twisting.

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Figure 2.21: preferred shear walls plan layout. (Google 2012)

2.5.3 Failure Mechanisms In the pioneering work of Paulay and Priestly (1992), they argued that there are five different mechanisms of failure for slender shear wall. The mechanisms are listed as the following: a. Ductile flexural tension failure as the tension steel yields in the vertical direction. b. Flexural shear failure as diagonal cracks appear in the web indicating shear cracks. c. Horizontal sliding failure occurring adjacent to the joint with the foundation due to construction joints or the like. d. Overturning failure due to the immense lateral loads applied. e. Flexural compression failure as the concrete at the bottom heal of the wall crushes and compression also due to extreme lateral loads.

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More failures could be observed in walls. However, these failures would be brittle failures which never should be allowed to in wall designs.

Figure 2.22: Types of shear walls failure (Russel 2015)

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Figure 2.23: Shear wall failure in Nepal (Google 2015)

Figure 2.24: flexural shear wall failure (Google 2015)

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Figure 2.25: shear failure in shear walls. (Google 2015)

2.5.4 Shear-Wall-Frame Interaction The division of lateral loads between the shear walls and the frame can be analysed using a similar frame system to the one shown in figure 2.21. The relative portion of lateral loads that is shared between the wall and the frame can be estimated by assuming that both the wall and the frame are two vertical cantilevers, that are fixed at the footing and connected at the top via single rigid link beam. The bending moment value at the top of the wall reflects the lateral stiffness of the connected frames. As the lateral stiffness of the frame decreases the value of the negative moment at the top of the wall decreases as well, reflecting the flexibility of the frame compared to the rigid wall.

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Figure 2.26: Analysis of shear wall frame (Wight 2009)

Figure 2.27: Types of shear walls-frame deformations (Google 2014)

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2.5.5 Coupled Shear Wall In the case of two or more shear walls or even two wall assemblies, a coupling beam (sometimes called a spandrel or a lintel) is connecting the walls together to resist lateral loads. When the coupled wall deflects, both axes of part A and A’ (Figure 2.29) deflect laterally creating immense shear deflections in the coupling beam. However, a localised cracking of the beam to wall connection reduces the angle the beam can deflect into when it is attached to the wall. It is the norm to assume the reduced stiffness of the beam and the above mentioned deflections and that can be represented by moving the connection point from the exterior face of the wall into the internal side of the wall by a distance hb/2, where hb is the depth of the coupling beam. Thus it is assumed that the walls are joint by coupling beams from B to B’, resulting in a beam deflection by the following formula: ΔB = (bw/2 – hb/2) tan θ

Figure 2.28: Hinged versus stiff coupled shear walls. (Wight 2009)

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Figure 2.29: Analysis of shear walls coupling beam. (Wight 2009) According to static equilibrium the moment and axial forces in both wall segments must be equal to the total axial forces, shear forces and moments in the entire coupled system. The moments at the basis of the two walls are equal to: Mw1 = Mo Iw1 / ( Iw1 + Iw2 ) Mw2 = Mo Iw2 / ( Iw1 + Iw2 ) Where Mo is the moment at the bae of the wall due to factored lateral loads.

2.5.6 Distribution of Forces Lateral load come in two forms, namely wind and earthquake loads. However, earthquake loading will be outside of the scope of this thesis. The percentage of lateral loads that each wall carry depends on each walls relative rigidity. It is common to assume that the slabs behave as a rigid diaphragm, linking the lateral displacements of the shear walls together and to neglect the displacements in the footings and the soil. Thus, in each structure the lateral loads are distributed to the shear walls only. Rigidity of the shear walls is defined as r = 1/Δ

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Where: Δ = the total of the flexure and shear deflections in the wall In general where the shear walls in the structure are of the rectangular and of the same material we find three different cases representing the rigidity of shear walls. Case 1: If Hw / Lw < 0.3, then the flexural deflections can be neglected. The rigidity of the element can be directly related to its web plan area. Case 2: If 0.3 < Hw / Lw < 3, then an equivalent moment of inertia Ieq is required to simplify the calculation of the shear wall rigidity. Ieq is defined as moment of inertia that would represent the sum of the flexural and shear deflection of the wall. Case 3: If Hw / Lw > 3, then shear deflections can be neglected and the shear wall rigidity will be directly connected to the total plan area of the shear wall section.

Figure 2.30: Ieq values in different wall configurations (PCA 2009)

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A shear wall may consist of more than one element to form a C, L and U shape. If these units have enough shear ties strength between them, then their strength can be added together to form a single unit, resulting in a great shear resistance. Considering case 2 I figure 2.30 which is the most common case in medium rise buildings, relative rigidity and Ieq must be calculated using the following procedure. 1. Determine the effective flange thickness using the minimum of 12t or Hw/10 2. Find area of the web Aw and area of the flange Af 3. Located the centroid based on the formula

4. Find Istrong-axis

using the formula

5. Use figure 2.30 to calculate Ieq 6. Calculate the relative stiffness of the shear wall by dividing Ieq with the sum of Ieq multiplied by n, where n is the number of effective flanges in the storey.

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Figure 2.31: Method of calculating effective flange width. (PCA 2009) Moreover, the lateral loads are distributed to each shear wall with accordance with its relative rigidity. It is common to design only for two direction of lateral loadings on structure. Each floor has two characteristic centres, namely, the Centre of Mass and the Centre of Rigidity (shear centre). It is known in the structural literature that the lateral load will be applied on the structure aligned with the Centre of Mass. If the eccentricity between the Centre of Mass and the Centre of Rigidity exceed the minimum value specified in the international building codes, then torsion must be considered. To locate the Centre of Rigidity, the following formula must be used: Centre of Rigidity =

∑[Ieq (∑ 𝑥̅ )] ∑ n Ieq

Where X is the centre of shear walls resisting Vx.

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Figure 2.32: difference between centre of rigidity and centre of mass. (Wight 2009)

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Figure 2.33: Different shapes of shear walls. (Google 2014)

2.5.7 Placement of Shear Walls Ideally, shear walls should be placed symmetrically around the outermost walls of buildings. Non-symmetric shear walls will create uneven loadings and possible undesirable torsion effects. Figure 2.34 shows few plans showing various locations of shear walls for a rectangular building.

Figure 2.34: Different shear walls configurations within a plan.

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2.5.8 Wall Reinforcement Design The reinforcement in shear walls usually consist of the following: a. Vertical reinforcement laid out in two layers on each face of the wall. Longitudinal reinforcement could be placed centrally in the wall if the section is less than 200mm wide in accordance with AS3600 provisions. b. Horizontal reinforcement spread uniformly along the length of the wall to resist shear and to provide crack control. AS3600 section 11 offers two distinct ways to design a shear wall, the methods presented as the following: 1. If the in plane bending effect are neglected and thus the wall section is purely in compression then the following procedure can be followed: (Note: the section can be assumed to be completely in compression even if lateral force is applied. (If e = M*/N* ≤ L / 6) 1.1 Compressive capacity may be computed using: 1.1.1

The simplified formula in section 11.5 stating the following

Nu = (tw - 1.2e – 2ea) 0.6 f’c

Where Nu is the ultimate strength of the wall per unit meter tw = Thickness of the wall e = eccentricity of the load. According to clause 11.5.2, for cast in situ floor on top of the wall, the load eccentricity may be taken as zero. However, the clause also state that emin = 0.05 tw. ea = additional eccentricity on the wall due to its slenderness taken as (Hwe) 2/ 2500tw 1.1.2

As a column in accordance with section 10 of the standards where vertical reinforcement is provided on each face.

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1.2 Shear horizontal capacity is computed using Clause 11.6, which states the following: The critical shear section in the wall is taken at Lw/2 or Hw/2, whichever the least. The design shear strength of the wall is composed of both steel shear strength and concrete shear strength to form Vu. Where Vu = Vuc + Vus < Vumax = 0.2 f ‘c (0.8 Lw tw) In accordance with Clause 11.6.3 the ultimate shear strength of a wall excluding the reinforcement Vuc shall be calculated using the following method: a. For aspect ratio of Hw/Lw ≤ 1 Vuc = (0.66√ 𝑓 ‘c – 0.21Hw √ f ‘c / Lw) 0.8Lw tw The Australian standards express the contribution of the wall reinforcement to the total shear capacity of the wall in the following term: Vus = pw fsy (0.8 Lw tw) Where pw is the minimum of the ratios of vertical reinforcement area and the horizontal reinforcement area ratio to the cross sectional area of the wall per meter run. b. For aspect ratio of Hw/Lw > 1 Vuc= (0.05√ 𝑓 ‘c + 0.1 √ 𝑓 ‘c / (Hw/Lw -1) 0.8Lw tw But not less than 0.17 √ 𝑓 ‘c (0.8 Lw tw) And where Vus = pw fsy (0.8 Lw tw) Where pw is the horizontal reinforcement area ratio to the cross sectional area of the wall per meter run. 2. If the wall is subjected to tension in any part of its section than the in plane bending effect must be considered and designed for with accordance with section 8 (beam sections). Moreover, horizontal shear must be designed with accordance with Clause 11.6 (point 1.2).

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Note: the critical shear section is used to check the flexural-shear strength of the wall.

Figure 2.35: Location of the critical shear section. (Wight 2009)

2.5.9 Effective Height Before continuing any further, the definition of Hwe is examined and research on the topic is presented in the section below. By definition Hwe is the effective height of the wall from floor to floor. The standards gives provision for the calculation of the braced height of the wall (Hwe) in section 11.4 of AS3600-2009. The buckling behaviour of walls changes with different restrained conditions of the wall. Walls may buckle in one-way or two-way actions. Knowing that the difference between these two behaviours is immense in terms of effecting the buckling capacity of walls. Intensive research was done in the past to examine these effects. The work of RC wall pioneers such as Pualay and Priestley, Saheb and Fragomani have advanced the design of RC shear walls in a great fashion that serves the need for economic designs today.

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Previously AS3600-2001 only included the effect walls restrained at top and bottom, and failed to recognise the importance of side restrains in affecting the capacity of shear walls, resulting in great differences between the predicted values from the simplified methods and real test values. (J.H.Doh and S.Fragomeni, 2006). Further the authors of “Ultimate Load Formula for Reinforced Concrete Wall Panels with Openings” argued the need to incorporate such restrained in the standards and further provided formulae for the effective wall height based on their extensive research and experience. When AS3600-2009 was released, it incorporated the effect of two restraints, three restraints and four restraints. This new clause greatly enhanced the effectiveness of the simplified method making it more reliable and adhere to test values. (J.H.Doh and S.Fragomeni, 2010)

Figure 2.36: Buckling of two-edge restrained walls vs four-edge restrained walls. (Doh 2010)

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AS3600-2009 clause 11.4 provide the following guidelines to calculate the effective heights of walls, where Hwe = kHw I.

One-way buckling as a result of floor diaphragms providing lateral support at the top and bottom of walls. a. K = 0.75 where the floor can provide restraint against rotation (Castin-situ slabs) b. K = 1 where floors cannot provide rotational restraint (Precast slab panels)

II.

Two-way bucking as a result of restraints from three sides only, provided by slabs and intersecting walls.

, must be larger than 0.3 or larger than one-way buckling factors.

III.

Two-way bucking as a result of four side restraints due to slabs and intersecting walls.

Moreover, Clause 11.4 continuous to give guidelines of designing walls with openings. The Clause includes the following for walls supported on four sides: 

The effects of the openings may be ignored in the case of the total area of openings being less than 1/10 of the area of the wall and the vertical height of any opening does not exceed 1/3 of the height of the wall.



The wall side of the openings may be assumed as unsupported side.

The clause also gives notice that for an intersecting wall to be considered as a lateral restraint, its length must be of a minimum of 0.2Hw.

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2.5.9.2 Background of Clause 11.5: (Simplified method) The following section will illustrate some of the assumptions taken in the derivation of the simplified formula (AS3600-2009): (the procedure is outlined in Doh, 2002) 1) Zero contribution from any reinforcement in the wall. 2) Top eccentricity is only considered (ignoring load eccentricity at the bottom of the wall). 3) The concrete uphold zero tensile strength. Figure 2.37 illustrates the deflected shape of a shear wall under vertical loading only. Where the stress distribution in the middle of the section is assumed to be linear, where “d” is the full length depth and σ is the maximum stress in the section. The derivation of the simplified formula using figure 2.37 is illustrated in the following steps: 

Nu is applied at an eccentricity from the middle = e/2 + ym

Where ym is the deflection in the middle height of the wall 

a = tw/2 – e/2 - ym



Using static equilibrium the line of action of Nu must match

a = d/3 

Therefore, d = 3/2 ( tw - e – 2ym )



The stress distribution resultant force is



Nu = ½ σ d



While the stress σ is limited to 0.8 f’c to satisfy linear stress assumption



Therefore, Nu = 0.6 ( tw - e – 2ym )



If the curvature distribution is idealised to a triangular shape the following

Nu = ¾ σ ( tw - e – 2ym )

deflection at centre will occur: ym = Hwe2Фm/8 

The above formula is obtained by using the deflection by integration of bending moment theory (Gere and Timonshenko, 1990).

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Moreover, since the deflection is approximate sinusoidal, then the factor 1/8 can be approximated to 1/π2.



The curvature in the middle of the wall is therefore: Фm = (σ/E)/d = 0.8 𝑓 ‘c / (Ec d )

Figure 2.37: Stress and strain in buckled shear wall 

For design purposes the full length depth d becomes ¼ tw and Ec is assumed to be equal to 1000 𝑓 ‘c .



Thus the middle deflection expression is as the following: Фm = 0.0032/ tw



Finally, when substituting the expression Фm into ym, the following formula emerges: ym = Hwe2/ (2500 tw ) and matches the expression of ea in the standard.

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2.5.9.3 Limitations of Clause 11.4 The main limitations of the simplified formula in AS3600-2009 section 11.4 is as the following: 1) Hwe / tw = 30, is the maximum slenderness ratio the formula allows for, except for walls where N* < 0.03 𝑓 ‘c Ag, then Hwe / tw = 50 is allowed. 2) 0.05 tw must be enforced as a minimum eccentricity. 3) The effect of reinforcement content is ignored. 4) The walls are subjected to in-plane vertical loading. In case of in-plane vertical loading and horizontal loading occurring together, then the simplified formula is used for vertical loads only and horizontal loads are designed for using section 11.6

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2.5.10 Walls Designed as Columns According to clause 11.2.1 (ii) walls subject to in-plane actions can also be designed as columns with accordance with section 10, except that requirements in Clause 11.7.4 my overwrite the requirements in Clause 10.7.4. However, the Clause also states that the reinforcement must be placed in two vertical layers. Moment amplification and effective length: Bases on second order analysis theory, the applied moments must be amplified by a factor of δ in order to account for the P-Δ effect and avoid non-linear analysis. Furthermore, the amplified moment is later checked with the moment capacity of the wall section. According to AS3600 a wall/column is considered slender is Le/ (D/3) ≥ 25, thus a second order analysis has to be conducted on such sections to account for their slenderness effects. M* = δ M*o Since the scope of this paper is focused on braced walls/columns only then the only magnifying factor would be δ = Km / ( 1- N* / Nc ) ≥ 1.0 Where Km = 0.6 – 0.4 M1*/ M2* where 0.4 ≤ Km ≤ 1.0 and where M1* and M2* are design moment on column ends. The axial buckling loads of the walls/columns is given by the following formulae: Nc = π2 [200 d0 (Ф Mub) / (1 + βd)] / (Le)2 Where Ф Mub is the bending design capacity of the wall and Ф = 0.6, also βd = G / (G + Q). The amount of moment magnification each wall suffers, greatly depend on its slenderness characteristics and effective height. A braced wall/column is considered short if Where Nuo is the axial ultimate capacity of the column cross section.

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It is important to note that using the column method the upper limit of slenderness is 120, which is equivalent to Hwe / tw = 36. Which is higher than the limit given by the simplified analysis formulae. Moreover, in the column method a minimum of 1% steel is required in the vertical direction, which is clearly much higher reinforcement than what is required by the simplified design method.

2.5.11 Reinforcement Layout Steel reinforcing bars are to be provided in walls in regularly spaced vertical and horizontal grids (Figure 2.11). The vertical and horizontal reinforcement in the wall can be placed in one or two parallel layers called curtains. Horizontal reinforcement needs to be anchored at the ends of walls. The minimum area of reinforcing steel to be provided is 0.0015 vertical and 0.0025 horizontal times the cross-sectional area, along each of the horizontal and vertical directions. This vertical reinforcement should be distributed uniformly across the wall cross-section. AS 3600-2009 imposed minimum limit on reinforcement places in walls. The detail of Clause 11.7 is as the following: 1) Vertical reinforcement cannot be less than 0.15% and the value of steel required for strength. 2) In general horizontal reinforcement of not less than 0.25%. Furthermore, Clause 11.7.2 stipulates values of horizontal reinforcement for shrinkages and crack control of walls as the following: 1) For exposure classification of A1 and A2: i.

0.25% for a minor degree of crack control.

ii.

0.35% for a moderate degree of crack control.

iii.

0.6% for a moderate degree of crack control.

2) 0.6% for exposure classification of B1, B2, C1 and C2 in any crack control degree.

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2.6 Column

Researched by: Mootassem Hassoun

Columns are vertical members that work mostly in


compression. Columns support building floor systems. They work by transferring the vertical loads from the structure into the foundation of the building. Columns’ cross section are relatively small compared to their height. While a column works mostly in compression, it is also subject to bending actions as a result of load eccentricity. Even under uniform area loading, edge columns will always experience moments due to load eccentricity.

Figure 2.38: Edge columns supporting high rise floor system Bending moments may occur on one principle axis of the column or it may occur on both axis simultaneously (Biaxial bending)

2.6.1 Columns with central loading Each column cross section has a unique point called plastic centroid. If the load coincide with the plastic centroid, then no moment will induced into the section.

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Figure 2.39: A column loaded through its plastic centroid. (Loo 2010)

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For the section shown in figure 2.39, the ultimate strength is: Nuo = α1 𝑓𝑐′ ( Ag- As) + Asfsy Where according to clause 10.6.2.2 of AS 3600-2009 α1 = 1 – 0.003 𝑓𝑐′ , however it should be within 0.72 and 0.85 Note: concrete ultimate strain in columns εcu = 0.0025 The position of the plastic centroid can be found by taking the moment of the ultimate strength about the top fibre of the column and divide by the ultimate strength. dpc =

𝛼1 𝑓𝑐′ (𝐴𝑔 −𝐴𝑠 )𝐷⁄2+𝑓𝑠𝑦 (𝐴𝑠𝑐 𝑑𝑐 +𝐴𝑠𝑡 𝑑) 𝑁𝑢𝑜

Centrally loaded columns are hardly found in practice. However, their ultimate strength is highly important to construct the interaction diagram of the column.

2.6.2 Uniaxial bending of columns Under eccentric loadings, the strain converts gradually from compression into tension as the load eccentricity or the eccentric loading increases. Therefore, steel must be induced to resist the tensile stresses in the section. Figure 2.40, shows the stress and strain distribution in the eccentrically loaded column.

Figure 2.40: Strain and stress diagrams in eccentrically loaded columns. (Loo 2010)

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The concrete resisting force and steel compressive force, respectively are: 𝐶𝑐 = 𝛼2 𝑓𝑐′ 𝑘𝑢 𝑑𝑏 And 𝐶𝑠𝑡𝑒𝑒𝑙 = 𝐴𝑠𝑐 (𝑓𝑠𝑦 − 𝛼2 𝑓𝑐′ ) The general equation for the force in the tension steel is: 𝑇 = 𝐴𝑠𝑡 𝑓𝑠 Where 𝑓𝑠 ≤ 𝑓𝑠𝑦 Using static equilibrium: Nu = Cc + Csteel - T = 𝛼2 𝛾𝑓𝑐′ 𝑘𝑢 𝑑𝑏 + 𝐴𝑠𝑐 (𝑓𝑠𝑦 − 𝛼2 𝑓𝑐′ ) − 𝐴𝑠𝑡 𝑓𝑠 By taking moment about the centre of the stress the block, the moment capacity can be found as: 𝑀𝑢 = 𝐴𝑠𝑡 𝑓𝑠 (𝑑 − 𝛾 𝑑𝑛⁄2) + 𝐶𝑠𝑡𝑒𝑒𝑙 (𝛾 𝑑𝑛⁄2 − 𝑑𝑐 ) At ultimate the compressive steel is assumed to reach yield, while the tensile steel may or may not yield. This situation gives rise to different failure modes which will be discussed in the following section. At the decompression point, the section is completely in compression. However, the strain varies from 0.003 at the compressive fibre to 0 in the opposite fibres. Using this feature in the decompression point, the forces in the steel and concrete are readily determined. The axial capacity of the section is represented by the sum of all the steel and concrete forces in the section. Moment capacity is determined by taking the moment of the forces in the section at the plastic point.

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Points above the decompression point on the interaction diagram cannot be determined using the rectangular stress block. Therefore, these points cannot be found using the ordinary stress block calculations. However, these points could be interpolated between the squash load and the decompression point. Balanced failure, the tensile strain in the steel reach 0.0025 at the same time as the concrete reaches the ultimate compressive strain 0.003.the load eccentricity that causes this condition is called eB . For eccentricities e < eB , the primary mode of failure is compressive failure as the concrete reaches its ultimate strain while the steel does not. For eccentricities e > eB, the steel yields before the concrete reaches its ultimate strain value, thus resulting in tensile failure. The column in the state of pure bending act very much like a doubly reinforced beam. The axial force is equal to zero. The depth to neutral axis is found by iterating until the sum of the internal forces is equal to zero.

Figure 2.41: Strain and stress diagrams in different stages of columns loading

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Figure 2.42: Column interaction diagram. (Slideshare 2012)

2.6.3 Biaxial bending AS3600 gives the following formula to check the capacity of column in biaxial bending: 𝑀𝑦∗ 𝛼 𝑀𝑥∗ 𝛼 𝑛 ( ) +( ) 𝑛 ≤ 1.0 ∅𝑀𝑢𝑥 ∅𝑀𝑢𝑦

Where 𝛼𝑛 = 0.7 +

1.7𝑁∗ 0.6𝑁𝑢𝑜

Moreover, according to Clause 10.6.3 in AS3600, for a rectangular column where D/b ≤ 3, the section may be design for N* with each M*x and M*y separately if the line of action of the resultant force falls within the shaded area in figure 2.43. Furthermore, the standards sets a minimum applied bending moment in each major direction to be 5% of the applied axial force.

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Figure 2.43: Limitation for line of action of resultant axial force in a rectangular column. (AS3600)

2.6.4 Short column design A column is designed as a short column if I satisfies the following requirements: 

For a braced column 𝐿𝑒 𝑟

𝑓′

𝑀∗

≤ min( 25, 𝛼𝑐 (38 − 15𝑐 )(1 + 𝑀1∗ )) 2

Where 𝛼𝑐 = √2.25 − 2.5𝑁 ∗ /(0.6𝑁𝑢𝑜 ) 

For an unbraced column Le/r ≤ 22

Le is the effective length of the column. It is taken as total length of the column for braced columns restrained by a Flat slab and 0.9 of the total length for columns restrained by beams. r is the radius of gyration of the column taken as 0.3 Depth for rectangular and diameter/4 of circular columns.

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Figure 2.44: Definitions of variable for a short column. (AS3600)

2.6.5 Slender columns In slender columns, the force and the lateral deflection can lead to a significant increase in the moment. The magnification of the moment is accounted for using either of the following methods. Second order elastic analysis or non-linear analysis, is a rigorous analysis done to find the P-Δ effect on columns. However, this analysis is quite complex and can only be performed by software. First order elastic analysis, is a method specified in the concrete standards to simplify the procedure of find the moment magnification factors. The rest of this section will address the method to find the magnification factors for slender columns. According to Timoshenko and Gere, the maximum moment along a pin ended column is: 𝑀𝑚𝑎𝑥 = δM

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Where the moment magnifier is: δ=

1 1 − 𝑁⁄𝑁𝑐

Nc is Euler Buckling load given by: 𝑁𝑐 = 𝜋 2 𝐸𝐼/𝐿2 However, for reinforced concrete there are rarely any pin end restrained and the moments at the ends are different most of the time. An allowance needs to be made to adjust the moment magnifier to include the above mentioned factors. Reinforced concrete columns normally have some degree of rotational restraint. To simplify the design process, the effective length is used as a substitute of the full length L. 𝐿𝑒 = 𝑘𝐿 For a braced column, k is less than unity. On the other hand, in case of a sway column, k is bigger than unity. For out-of-plane analysis, usually the effective height is needed. In that case, a simplification is offered by the standards, which is the find k directly by using figure 2.45 and assessing the end restraints of the column.

Figure 2.45: Effective length factor for columns with simple end conditions. (AS3600)

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Where a column is part of a regular framed structure, the ends of the column will be partially restraint. The degree of restraint provided by the frame to the column depends on the stiffness of the connected elements to the column. To find the flexural stiffness of the column ends, the restraint coefficients γ1 and γ2 must be evaluated. 𝛾=

𝛴(𝐼/𝐿)𝑐 𝛴((𝛽𝐼)/𝐿)𝑏

Where: 𝛴(𝐼/𝐿)𝑐 is the sum of the inplane bending stiffness of the columns connected to the ends of the column being considered. Note that Ic must be reduced to 0.8 Ig as the column section will most likely crack. 𝛴(𝐼/𝐿)𝑏 is the sum of all the inplane bending stiffness of all beams and slabs connected at the end joint of the column being considered. Again Ib must be reduced to 0.4Ig to considered cracking of the section. β is a fixity factor given in table 2.6.

Table 2.6: Fixity factor values. (AS3600) After the end restraint have been calculated, the effective length factor ‘k’ can be found using figure 2.46 and 2.47.

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Figure 2.46: Effective length factor for braced column. (AS3600)

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Figure 2.47: Effective length factor for sway column. (AS3600)

Warner et al. (2007) state that for the purpose of evaluating the buckling load, finding the flexural stiffness could be quite complex. The stiffness is equal to: EI = M /κ According to MacGregor et al. (1975) the values at the balanced failure condition, Mub and κub can be used to estimate EI. κub = ε / dn = 0.003 / (0.545 d) = 1/ (182 d) Furthermore, to allow for a column capacity reduction due to creep and shrinkage, the flexural stiffness is divided by ( 1+ βd).

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Chapter 2: Concrete design Where βd = NG/ ( NG+ NQ) Therefore, the flexural stiffness is: EI =

182𝑑𝑜 ∅𝑀𝑢𝑏 1+𝛽𝑑

The buckling load is taken as the following formula Nc = (π2 182 do φMub) / (Le2 ( 1+ βd)) The braced moment magnifier is:

𝛿𝑏 =

𝑘𝑚 1−𝑁∗ /𝑁𝑐

≥1

Where km = 0.6 -0.4 (M*1 /M*2) ≥ 0.4 The sway moment magnifier is:

𝛿𝑐 =

1 1−𝛴𝑁∗ /𝛴𝑁𝑐

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Chapter 3: Cross Laminated Timber

Capstone B

Chapter 3: Cross Laminated Timber (CLT)

Researched by: Osman El-Zohbi Written by: Osman El-Zohbi

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3.1 Cross Laminated Timber (CLT) CLT is the name for Cross laminated timber, “the engineered wood of the future…

First

developed

in

Switzerland

in

the

1970s”

according

to

woodsolutions.com.au. Essentially, CLT is timber assembled into panels consisting of “several layers of boards stacked crosswise (typically at 90 degrees) and glued together on their wide faces” (p 15/594). A standard CLT panel is fabricated with 3, 5 or 7 layers, however this may be exceeded for special cases. An important point of consideration is that Canada has produced a handbook covering design of CLT panels with 3, 5 and 7 layers. For special cases, 9 or even 11 layers can be manufactured and used e.g. for a ground slab. Other variances of CLT panels include having consecutive layers placed in the same direction, giving a double layer; this is normally the case for 9 or 11 layer CLT panels.

Figure 3.1: CLT single and double layer cross sections. (FPinnovation 2011)

Figure 3.2: Standard CLT panel (assume section B-B is longitudinal). (FPinnovation 2011)

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Thickness and width of individual timber sections are determined based on the sizing and grade of timber the manufacturer uses. Panel sizes vary according to manufacturer capabilities and designer specifications but usually don’t exceed 4m by 18m. In Australia the standard timber thickness is either 35 or 45mm. CLT has some similarity to glulam, however, the key differences are that glulam has all layers assembled and loaded in one direction; parallel to the grain. Cross laminated timber has longitudinal and transverse layers with different loading directions and angles.

Figure 3.3: CLT and GLT. (FPinnovation 2011) Typically slabs, walls and lintels would be the main structural elements designed with CLT. FPI innovations Canada developed a handbook using European codes to provide in depth explanation of CLT, its uses and the various calculations used for forces and capacities of elements. A North American handbook was also developed by FPI to allow CLT construction for American codes and units. After reading this, it was noted that while the Canadian handbook focuses on designing slabs and walls, the North American handbook includes columns. Designing walls was deemed simpler and chosen so the Canadian handbook was used instead. Default assumptions made include the use of Douglas fir wood with density of 550kg/m3 and initial moisture content of 12%.

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Currently, Lend Lease is the only Australian company to build with CLT and has set the world record for the tallest timber building. Refer to the case studies section for more detail. An important feature of CLT is that it can be used for structural loading bearing members, facades and even furniture.

3.2 CASE Study 3.2.1 Forte Lend Lease

Figure 3.4: pictures showing the construction of Forte building.

Figure 3.5: 3-D model of forte. (KLH 2012)

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In Australia, Lend lease has so far been the only engineering company to incorporate CLT. Lend lease has used CLT as a primary building material for high rise structures in Victoria- An example would be the Forte building which holds the record for the largest timber structure worldwide. The apartment building stands at over 30m with 10 storeys and a weight of 485 tonnes. Approximately 759 panels of CLT were used for the apartment; the timber used is European spruce delivered from Austria. Each panel was cut to specific dimensions from CAD drawings before shipping to ensure accuracy and simplicity of assembly. Woodsolutions predict the effect of using CLT in the structure will sequester 761 tonnes of Carbon Dioxide; this would almost double when considering the effect of building with steel or concrete. The result is a lightweight apartment building with a 5 star green rating saving residents $300/ year on energy and water. Forte was built in approximately 8 months with the CLT installation taking 2 months. 13mm and 16mm plasterboard layers were installed on walls and floors to achieve Fire resistance ratings of 90/90/90. This is ideal for a timber high rise. The concrete basement and ground floor slab provide protection against termites and water proof membranes are used to protect against weather. According to Lend Lease, the building has the structural strength to carry up to 25 storeys without adjusting the design. This is the result of the conservative measures taken when designing the structure; the concrete basement had the addition of deep driven piles more than half the height of the building, providing more than double the necessary foundation strength.

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3.2.2 Stadthaus, Murray Grove

Figure 3.6: Stadthaus building. (Trada 2012)

Figure 3.7: Stadthaus building construction (Trada 2012)

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Stadthaus is a nine storey apartment building in the UK built primarily from Cross Laminated Timber. The ground floor is concrete while the other eight storeys are Cross Laminated Timber. The residential building has 29 apartments made entirely from CLT; including stairs floors and walls. A prime example of 21st century architecture, the Stadthaus building paved the way for timber high rise construction around the world. The CLT is formed from ‘Jumbo plywood’ that is light weight and easy to assemble onsite. The main appeal with CLT came from its ease of replenishment and simple installation assisted by KLH design manuals. The apartment building was made of 25000 CLT panels, made of 70% waste timber. The timber came from dedicated ‘timber farms’ in Austria. All load bearing elements of the building such as lift shafts, stairwells and all external walls provide exceptional strength and sound resistance between apartments and lifts. In order to ensure satisfactory damp proofing, concrete was used for the ground floor rather than CLT. The structure was assembled in nine weeks using mobile cranes rather than tower cranes to lift panels into position and a ‘platform construction’ configuration; this meant each floor was set on the walls below before another storey of walls was raised into position. Additionally, only a four man crew was required onsite three days a week to complete the structure. All joints were secured with angle plates and screw joints. The high acoustic performance was an important design consideration as traditionally, timber structures have poor acoustic performance when compared against concrete. Fortunately, CLT has a high density and its layer principle overcomes issues with transference of sound. Both sound and fire performance exceed UK requirements. In summary, the construction of the stadthaus apartment building was a revolutionary project that was more economic than concrete construction and paved the way for future CLT construction projects.

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3.2.3 XLam NZ XLam is a company in New Zealand that entered the CLT manufacturing and shipping business in 2011. With an abundance of timber resources and a need for sustainable structures that could resist earthquake loads; they were the first manufacturers of CLT in the southern Hemisphere. Currently, they’re website provides detailed structural design resources such as panel configurations and span tables to act as guides for anyone desiring to build with CLT. In order to verify the accuracy of our calculations; we initially adapted the formulae presented in FPInnovations’ Canadian handbook for CLT to work within Australian standards and compared them to tables and resources provided by XLam. Our results matched XLam; confirming our calculations and allowing for us to alternate reference XLam when necessary. In New Zealand, the timber grades and qualities are extremely similar to Australia with only minute differences as shown in the tables below. Australian timber has 35mm and 45mm thicknesses while NZ has 20mm and 35mm. Additionally, Australia uses F grades while New Zealand timber has G grades with very similar Elasticity values that could almost be interpolated from Australian Standards.

Table 3.1: Characteristic Strength Values. (AS1720.1-2010)

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Thickness

Grade

Modulus of Elasticity

20mm

G10

E0 = 10 000 MPa

20mm

(length of the screw – threaded length) (t = thickness of the panel) 4. If the threaded part of the screw is placed in the shear joint, deff = 1.1 d2 5. Fv,Rk = √(2 x MyRk x fh,1,k x d ) 6. Fax,a,Rk = (80x10-6 x ρk2 x leff x d)/4 7. Design shear capacity Fv,Rd = 2 ( Fax,Rd x 2/( spacing x √2 )

Figure 3.27: Shear action on double lap joint (Storaenso 2014)

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Figure 3.28: Long section of the double lap joint. (Storaenso 2014)

3.4.8 CLT Connection Structural Analysis The CLT connections between the panels were modelled in ETABS using shear link elements. The screws between the panels are represented in the model by their slip stiffness modulus. The equation used to find the slip modulus of self-tapping screws is as the following: Kus = ρ1.5 𝑚 d / 23

(Eurocode-5)

Therefore, if an 8mm diameter screw was used, it will result in Kus = 3888.9 kN/m. Considering the minimum spacing of 45 degree inclined double screws, the minimum spacing allowed by the EC-5 is 56mm. Due to the large number of screws needed, the modelling of the connection must be simplified in the software. The springs were distributed every meter in walls and between CLT panels and they were assigned portion of the total stiffness of the joint in that particular floor.

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Chapter 4: Loading Capstone B

Chapter 4: Loading Researched by: Osman EL Zohbi Written by: Mootassem Hassoun

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Chapter 4: Loading Capstone B This section will explain the loading applied on the building. According to AS1170.0, there are five types of loading on buildings. However, we will only deal with four. The loadings applied on the structure are as the following: Self-weight is the dead load the structure has to carry due to its density. The densities of materials used in this project are listed in the table below:

Concrete 24 ϒ (kN/m3)

Steel 77.77

Timber 5.5

Table 4.1: values of unit weight of materials used in the model. Super imposed dead load is the load resulted from building weights that are not part of the structural skeleton of the building. Weightsused included services, tiles and walls Table 4.1: values of unit weight of materials in theare model. partitions. The Super imposed dead loads are as the following: kN/m2 fibrous plaster ceiling 0.09 Brick masonry 0.19 tiles terracota 0.57 suspended metal lath and gypsum paster 0.25

Table 4.2: Values of super imposed dead load. Live load on the structure is determined by table 3.1 in AS1170.1 as 1.5 kPa for selfcontained dwelling.Figure 5.1: ETABS model of the proposed building.Table 4.2: Values of super imposed dead Total vertical load is expressed as 1.2G+1.5Q = 9.57 kPa is larger than 1.35G = 8.23 load. kPa. the total vertical loading Fd = 9.57 kPa

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Chapter 4: Loading Capstone B Wind loading is calculated in accordance with AS1170.2. The building falls into the category of section A2 and A3 (Sydney, suburban, generally flat, no shielding, importance level of 2) For the above mentioned characteristics, the return periods is 500 years for strength. Regional wind speed VR = V500 = 45 ms-1 Since the building is near a city, thus it falls in terrain category 3 and the following factors apply. Md = 1 ( conservative value to ignore the direction effects and since the location of the building is unknown it is reasonable to adopt 1 ) Mz.cat = 0.97 Ms = 0.95 ( conservative in absence of building location ) Mt = 1 ( for flat roofs )  Vdes,θ strength = V500 Md Mz.cat Ms Mt = 45 x 1 x 0.97 x 0.95 x 1 = 41.46 ms-1

Design pressure = 0.5 pair Vdes,θ2 Cfig Cdyn Pult = 0.5 x 1.2 x 41.462 x Cfig x Cdyn x 10-3 = 1.031 Cfig Cdyn 10-3 kPa Approximate first mode frequency for the building of height = 24 m Frequency = ( 46/ h ) Hz = 46/24 = 1.916 > 1  Adopt Cdyn = 1

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Chapter 4: Loading Capstone B For direction of the wind in θ = 90o and θ = 0o Cfig, windward wall = Cp,n Ka Kc Kl = 0.7 x 1 x 0.9 x 1 = 0.63 Cfig, leeward wall = Cp,n Ka Kc Kl = -0.5 x 1 x 0.9 x 1 = -0.45  Adopt Pwindward = 1.031x0.63 = 0.65 kPa Pleeward = 1.031x-0.45 = -0.46 kPa

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Chapter 5: Computer Modelling and Design

Capstone B


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5.1 ETABS Model 5.1.1 General Modelling Researched by: Mootassem Hassoun

5.1.1.1 Description


The model is an eight storey concrete shear wall and frame building that contains elevator and stair cores in its centre. The building is subjected to vertical static loading and computer-generated wind loading per the AS 1170.0, 1170.1 and 1170.2. The building consists of concrete slab and columns on every level. Please refer to Figure 6.1 for a three dimensional view of the structure.

Figure 5.1: ETABS model of the proposed building (ETABS 2015)

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5.1.1.2 Model Start-up The model created will be analysed and designed on the basis of AS 3600-2009. The units used in this model are the System International units only. The input is displayed in appendix A.

5.1.1.3 Create Grid System The grid definition for this model contains Cartesian coordinates system only. The grid spacing in the X and Y directions are uniform at 4m spacing and a number of 6 grids in each direction. In this case it is the easiest to use the grid template in ETABS .

5.1.2 Material Definition The material used in this model will be 32Mpa strength concrete with an Elastic Modulus of 30100 and 500Mpa yield strength for the rebar. Please view figures 3-6 in appendix A to check material input.

Type Concrete Steel

Elastic Strength modulus 32 500

30100 20000

Unit weight 3

kN/m 24 77.7

Table 5.1: Material input to ETABS .

5.1.3 Sections Definition

5.1.3.1 Columns The columns in this model will have unified section properties through the entire building. The columns will be assigned a 300X300 section. Moreover, the section stiffness will be modified to correctly model a cracked section in ETABS and obtain results as a close to the real model as possible. According to ACI 318-11, cracked columns should be modelled with and Icr = 0.7 Ig. These values will be imported. However, to avoid torsional design of the columns, the torsion modifier will be set to 0.01 to avoid such problem.

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Chapter 5: Computer Modelling and Design Cross section

Shape

Ixx

Iyy

300x300

Square/ rectangular

0.7

0.7

Capstone B

Table 5.2: Column’s properties input into ETABS .

5.1.3.2 Slabs The floor slabs will be assigned a 200 mm wide section with a thin shell finite element. Slab elements will be modified by a factor of 0.25 to correctly model a cracked slab behaviour and to coincide with the ACI recommendations for slabs. Thicknes 200

Type Shell-thin

Mxx 0.25

Myy 0.25

Table 5.3: Slab’s properties input into ETABS .

5.1.3.3 Walls The shear walls will be assigned a 200mm thick sections all along the model. The crack modifiers for the shear walls will be 0.35 to correctly study the behaviour of cracked shear walls in out-of-plane bending. Input screenshots in appendix A.

Thicknes 200

Type Shell-thin

Mxx 0.35

Myy 0.35

Table 5.4: Wall’s properties input into ETABS .

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5.1.4 Floor Diaphragms Assigning a diaphragm to an area object provides a diaphragm constraint to all of the corner points of the area object and to any additional point objects that are enclosed within the boundaries of the area object. This includes any points (joints) that are created as a result of automatic area object meshing. Diaphragms can be horizontal only. Thus diaphragm assignments are not applicable to wall-type and ramp-type area objects. They are applicable only to floor type area objects and to null-type area objects that happen to be in a horizontal plane.

Figure 5.2: Floor diaphragm assignment in ETABS . (ETABS 2015)

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5.1.5 Frame Connection The members in the frame are all fixed connections. The connections of the structural members to the footings are also fixed connections.

5.1.6 Loadings The structure will have four types of loadings, namely self-weight, Live load, Super Dead and Wind load. Self-weight is automatically computed by ETABS with accordance with the material unit weights imported to it. Live Load in accordance with AS 1170.1 and as the structure is a residential structure it will be assigned 1.5 Kpa in accordance with Table3.1. Furthermore, the live load will exhibit a reduction factor also in accordance of 1170.1 Clause 3.4.2, the reduction factor is automatically computed by the software. Super Dead loading will be in the form of area loading and line loading with accordance with the AS1170.1. The area loading corresponds to tiling and will give a value of 0.57Kpa. The line loading is coming from the partition walls. Walls are assumed to be from 110mm brick walls thus with accordance with Boral technical manual the unit weight of the brick is 2.9kg/m3 resulting in a line load of 9.4kN/m. Wind Load is automatically generated by ETABS with the guidance of AS1170.2. Moreover, the user must input wind load values as shown in the table 5.5. Wind load is further divided into two components Wx and Wy as wind cannot come from both directions in the same time, thus, each wind component will be considered separately. The wind load values and moments given by ETABS were checked manually to ensure the windward and leeward pressures are truly consistent with the guidelines of AS1170.2.

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Regional wind speed 45

Terrain category 3

Combination

Direction multiplier

1

1

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Area Local Porous reductio pressure Cladding n 1 1 1

Dynamic Sheilding Topographic Response multiplier multiplier Factor 1 1 1

Table 5.5: Wind input parameters into ETABS . Furthermore, the following load combinations are input into ETABS : Load combinations are as follows: 

0.9G+Wx



0.9G+Wy



0.9G-Wx



0.9G-Wy



1.2G-0.4Q+Wx



1.2G+0.4Q+Wy



1.2G+0.4Q-Wx



1.2G+0.4Q-Wy



1.2G+1.5Q



1.2G+Wx



1.2G+Wy



1.2G-Wx



1.2G-Wy



1.35G

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5.1.7 Concrete Frame and Shear Wall Design For concrete frame design, ETABS automatically generates all the correct parameters to match the AS3600-2009 design standards. The design codes for the concrete and shear walls have already been defined. After running the analysis, the design portion of the program can be performed. The analysis is based on section properties defined earlier, and thus the design forces are based on these analysis section properties. Values are displayed in appendix A.

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Figure 5.3: Screenshot of ETABS output for column design. (ETABS 2015)

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The column check is displayed in appendix B. According to ETABS output, all the columns have passed with the highest design ratio of 0.934. Note that the columns cross section is only 300X300 and includes 3N20 on each face.

Figure 5.4: Screenshot of ETABS output for Wall design. (ETABS 2015) Once again, according to ETABS output the shear walls are safe and with a design capacity ratio of only 0.003. These results are subject to manual check later in this report.

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5.1.8 Analysis and Results The results for bending moment displayed in appendix B. Note: the bending moment values are for 1.2G+1.5Q combination. The results for axial force in the frame are presented in appendix B.

5.1.9 Shear Wall Moments The output results of the model are displayed in detail in appendix B. Notice the moment in the cores are discontinuous and at each floor the moment decreases and increase again on the next floor. This is due to the lateral restraint the intersecting walls are providing on each floor. Whereas, the external walls exhibits perfect cantilever moment due to the lack of lateral restraints in the y-direction.

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5.2 SAFE 5.2.1 Background The program SAFE is another software by the pioneer CSI. The software is used to analyse slab, beams and footings using the Finite element method and recently including the traditional equivalent frame method. SAFE has the capacity to analyse 3D finite elements which ETABS has a shortage doing. This feature enables SAFE to perform an accurate analysis of flat elements. Moreover, SAFE has a special feature that allows it to perform a cracked section analysis to provide the most accurate results compared to any other finite element software in the market today. Finally, SAFE has a list of international standards data base including up to date AS3600-2009. This data base enables SAFE to perform a complete ultimate and serviceability check and design of structures. The only noticeable shortage in SAFE that it does not include the reinforcement needed for shrinkage and crack control in the reinforcement design. However, such shortage can be easily made for using a simple excel sheet. The team will be using SAFE to analyse and design the floor slabs and the raft foundation of the building.

5.2.2 Advanced Deflection Calculations SAFE incorporates in its design the deflection using the age adjusted Elastic modulus of concrete describe in Eurocode 1992. Moreover, the program finds the cracked section properties using multiple iterations. However, due to the lack of the absence of this method in AS3600-2009 the team will rely on simple deemed to comply formula programed in spread sheet to check deflection.

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5.2.3 Modelling Simply the floors are exported from ETABS with their loads and displacements then later imported to SAFE to complete the analysis. In SAFE the load and load combinations are defined before the analysis can begin.

Figure 5.5: Slab modelling in SAFE. (SAFE 2015)

As previously discussed the long term deflections in the slab were determined and shown in the figures in appendix C using SAFE non-linear cracked section analysis.

5.2.4 Deflection Checks 5.2.5 Ultimate Limit State Design After running the model and having the applied moments and stresses determined as shown in the figure below, the slab was ready to be designed for the ultimate limit state. Input and output are also displayed in Appendix C.

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Figure 5.6: Punching shear calculation sheet as produced by SAFE. (SAFE 2015)

5.3 CSI Column CSI Column is used to have a closer look at the most critical column in the structure. The team ought to provide satisfactory detailed design before claiming that the concrete frame system had passed the ultimate load test. CSI column is a powerful tool that can easily and accurately provide the capacity of any column cross section no matter how arbitrary the shape is. Moreover, the strength of CSI column lays in its ability to produce powerful stress diagrams that reflects the stress distribution state in the composite column. Finally CSI is also used to locate the location of the neutral axis in the section.

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Cracked concrete

Figure 5.7: Shows the position of the neutral axis in the section. (CSI column)

Figure 5.8: Shows the stress values in the bars. (CSI column)

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5.4 CLT Modelling 5.4.1 Background Cross laminated timber is relatively a new material in the market and research is running on full time to discover its characteristics. Due to the ambiguity in terms of research on the material the team could not find a research paper that gives reference or guidance on how to correctly model CLT frames. Based on the above, the team investigated the CLT frame behaviour and with the help of our supervisor, a CLT model was created to allow this project come as a close as possible to the natural behaviour of a CLT frame.

5.4.2 Modelling the Frame The building is modelled using ETABS as a finite element analysis software. The model consist of the exact geometry the concrete model has, except that the internal partitions and external cladding in the previous models are now load bearing CLT panels.

Figure 5.9: Typical CLT floor plan. (ETABS 2015)

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5.4.3 Preliminary Member Sizing Since CLT is new material, it was very hard to give a rough estimate to the section properties without any initial calculations or studying of the subject. Therefore, the team had intensively researched CLT and found some very important reliable sources that helped understand this material. Finally, a spreads sheet program was written to design and size the members under a specific load input. The program was used to initially find a rough timber grade and a CLT section to start the analysis with. After few iterations, a final size was chosen and modelled in ETABS then checked back in the spreadsheet to confirm the design ratio.

Figure 5.10: The spreadsheet program used to design CLT.

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5.4.4 Materials Based on the above written paragraph, a grade F11 timber was used as the optimum strength characteristics for such building. The sections were found to be consistent of three layers only, reducing the dead load and resulting in an economical design. However, two extra sacrificial layers are added for fire resistance as it will be shown in chapter 6. The input into ETABS is shown in appendix D.

5.4.5 Element Sections Bases on multiple iterations between ETABS and the program, the ideal section heights were found and displayed in the appendix D.

5.4.6 Modelling Techniques Upon researching and after few meetings with the supervisor, the team decided the following to correctly model the structure: 

All the CLT connections to the ground slab and foundations are to be modelled as perfectly pin connections, allowing for three degrees of freedom.



The CLT floor is to be modelled as beams spanning one way and to have the maximum manufacturing width when possible.



The CLT floor panels connections to the walls is idealised as a perfect pin. The reason is to avoid complications in considering semi rigid connections and to be on the conservative side as the floor panels will endure larger positive bending from a pin-pin connection. Last benefit from such idealisation is to avoid negative bending in the panel as the CLT panels do not work well in changing from positive to negative bending like RC frames do.



Only major walls in the floor plan are to be from load bearing CLT panels.



The service core of the building is made from reinforced concrete and is to match the core in the RC frame model.



The loading on the CLT model matches the load in RC frame model.



All the joints in a plane are connected through floor diaphragms.

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Figure 5.11: Full CLT model in ETABS 2015.(ETABS 2015)

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5.4.7 Output results All analysis results are displayed in Appendix E.

5.4.8 CLT Design and Check After attaining the applied internal forces in the CLT the members, the maximum applied force was designed for in the spread sheet as the following: 1. Slab panels observed to have a maximum bending moment of 42.11kN.m and a maximum shear force of 20.8kN. By inputting a 3 layer CLT panel constructed from F11 timber grade with 8 meter span and 4m wide, the panel capacity was found to be 123 kN.m > 42.11 and a shear capacity of 32.65 kN > 20.8, thus the panel passes with 3 layers and a total depth of 95mm. 2. Wall panels have the following maximum loads: Case 1 Axial load = 568.5 kN

Case 2

Axial load = 411.1 kN

Shear force = 23.2 kN

Shear force = 79 kN

In-plane moment = 136 kN.m

In-plane moment = 184 kN.m

Based on the spread sheet a wall panel with a dimension of 10m long and 3m height would have the following capacities: 1) Axial load = 3881 kN 2) In-plane bending = 20253 kN.m 3) Shear = 95.37 kN It is prominent that both extreme wall cases have passed. It is important to say that if a lower grade timber was used, the shear capacity would be 76 kN, thus F11 grade timber is the absolute minimum grade.

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5.5 Foundation Design SAFE software is employed to model, analyse and design the foundation of both buildings. The software possesses few features in foundation design that other structural analyses software lack, making SAFE ideal for this step. The foundation is analysed using the finite element method and the process of modelling the foundation is described below: 1. Import the base floor and the loads above from ETABS to SAFE. This step will provide the necessary loading values as ETABS calculated on the foundation to initiate the design. 2. Import the floor plan as a DXF file. The floor plan will help in positioning elements such as the Mat foundation and support. 3. Input material properties used in this model. The material used will be 32Mpa concrete and 500Mpa steel rebar. 4. Define section properties of the Mat foundation. The properties would include type of foundation, material used and thickness of the section. 5. Define section properties of the stiff plate. This type of element is input into the model to represent the cross section of the column that intersect with the foundation. As it is known the column fixity to the foundation is not supposed to deform, thus it represented as a stiff element. This element also enhances punching shear calculations. 6.

Draw all the elements on the plan in the best way that represents the reality.

7. Select the Mat foundation and assign to it soil subgrade support. The soil subgrade modulus (Ks) represents the bearing capacity of the soil and also its ability to deform under such loading. Lots of complicated formulas are involved in calculating Ks, except for one simple formula by Bowls. The formula states that Ks = 40 (FOS) BC. Where FOS is the assumed Factor of Safety when calculating the bearing capacity and BC is the bearing capacity of soil. 8. Subdivide the foundation in design strips in the X and Y directions. 9. Run the model to extract the result.

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5.5.1 RC Building Mat Foundation Design

Design

Soil

Spring

Stiff

Column

Figure 5.12: The layout of the Mat foundation.(SAFE 2015)

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Figure 5.13: Shows the column and design strips distribution in the slab.(SAFE 2015)

Comments: The bearing pressure on the soil did not exceed the allowable bearing capacity. Since Bearing pressure = -150 < -200 Kpa (Bearing capacity)

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In the x-strips, the column strips and middle strips vary in width to accommodate for the locations of the columns and walls. Moments computed are analysed based on one meter unit width of the strip. Results in appendix H. Comments: Reinforcement needed in the X-direction will be as the following: Bottom

N20@ 200 resulting 1570mm2/m more than the minimum

steel

required 1416mm2/m.

Top steel

N16@200 resulting in 1000mm2/m more than the minimum required 816mm2/m.

Table 5.6: Recommended steel in the x-direction.

Comments: Reinforcement needed in the y-direction will be as the following: Bottom N24@ 225 resulting 1570mm2/m more than the minimum required steel

1916mm2/m.

Top

N16@300 resulting in 667mm2/m more than the minimum

steel

required 616mm2/m.

Table 5.7: Recommended steel in the y-direction.

Note: Y-direction is the primary direction in this case.

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5.5.2 CLT Building Foundation Design

Figure 5.14: CLT foundation layout. (SAFE 2015) Comments: Reinforcement needed in the x-direction will be as the following: Bottom

N20@ 280 resulting 1107mm2/m more than the minimum required

steel

1090mm2/m.

Top

N16@300 resulting in 667mm2/m more than the minimum required

steel

568mm2/m.

Table 5.8: Recommended steel in the x-direction for CLT Raft.

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Comments: Reinforcement needed in the y-direction will be as the following: Bottom

N20@ 280 resulting 1107mm2/m more than the minimum required

steel

1099mm2/m.

Top

N12@240 resulting in 458mm2/m more than the minimum required

steel

448mm2/m. Table 5.9: Recommended steel in the y-direction in the CLT Raft.

Note: The maximum soil pressure is 116.05KPa, about half the Soil bearing pressure capacity.

5.5.3 Foundation Summary

5.5.3.1 RC-Building Provide 500mm thick Mat foundation from 32MPa concrete and reinforced with the following: Top x-direction

N16@200

Top y-direction

N16@300

Bottom x-direction

N20@ 200

Bottom y-direction

N24@ 225

Table 5.10: Foundation summary for the RC-Building Raft.

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5.5.3.2 CLT-Building Provide 300mm thick Mat foundation from 32MPa concrete and reinforced with the following: Top x-direction

N16@300

Top y-direction

N12@240

Bottom x-direction

N20@ 280

Bottom y-direction

N20@ 280

Table 5.11: Foundation summary for the CLT-Building Raft.

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Chapter 6: Manual Calculations

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Researched by: Mootassem Hassoun Written by: Mootassem Hassoun

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6.1 Building Manual Analysis and Design In this section, the building will be designed manually using the best approximation available in literature and practice. However, it is expected to get big variance between this manual analysis and the finite element analysis performed by the computer. Nonetheless, manual analysis is necessary to conduct to verify the computer analysis. Four components of the building will be analysed and designed in this section. The section to be designed are listed as the following: 1. Flat slabs 2. Columns 3. Shear walls 4. Foundation

6.2 Flat slab The slab system used in this building is a flat slab system with no perimeter beam or drop panels. The slab will be analysed with accordance with the direct design method guidelines provided in AS3600-2009.

6.2.1 Flat Slab Analysis The direct design method is only valid in the presence of the following conditions: 

The slab should include minimum two spans in each direction;



The supporting grid in any design strip must be aligned with a tolerance of each individual support be offset by a maximum of 10% from the centreline of the strip;



In any design strip, the ratio of any long span to short span must be less than two;



In any design strip, the adjacent spans must not differ by one-third and in any case the end-span must not be longer than the adjacent interior span;



All lateral forces on the structure must be resisted solely by the shear-walls or braced frames;



Vertical loads are uniformly distributed;



The live load is not twice bigger than dead load.

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Figure 6.1: Design strips layout. When examining the geometrical requirement of this conditions, it was found that manual analysis of the slab cannot be applied in this case. The only exceptions are spans in grid 3 and 5. Therefore, the analysis will only be conducted on grid 5 to illustrate the steps in designing a flat slab using the direct design method. The direct design method relies on fixed moment factors that depends on the type of spans used. The following tables are extracted from AS3600-2009 and are used in the analysis as it will be illustrated in this section.

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Type of slab system and edge rotation Exterior negative Positive moment Interior negative restraint moment factor factor moment factor Flat slabs with exterior edge 0.25 0.5 0.75 restrained by columns only

Table 6.1: Design moment factors for an end-span (AS3600-2009)

Type of slab system All types

Negative momnet Positive moment factor factor 0.65 0.35

Table 6.2: Design moment factors for an interior span.

The moment distribution factors applied in the above tables are for the design strip which includes both column and middle strip. Therefore, these factors must be further distributed to the column and middle strip in the following proportions: Bending moment under consideration Negative moment at an interior support Negative momnet at an interior support without spandrel beam Positive moment at all spans

Column strip 0.8

Middle strip 0.2

0.85

0.15

0.6

0.4

Table 6.3: Distribution of bending moment within the design strip (AS36002009)

As a result of the above mentioned moment distribution factors. The following simplified diagrams are produced to illustrate the moment diagrams in the design strip:

Figure 6.2: Column strip distribution factors.

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Figure 6.3: Middle strip distribution factors.

6.2.2 Moment Calculation Static moment Where Fd = 9.57 kPa Lt = 4 m and Lo = 4 – 2x 0.7 x 0.3 = 3.58 m

Mo = 61.32 kN.m

Therefore, the bending moment diagram in the column strip

and design strip will take the following shape and values:

6.2.3 Reinforcement Design At mid-spans: d = 200 – 25 – 12/2 = 169 mm assuming N12 bars f 'ct.f = 0.6 √32 = 3.4 MPa Pmin = 0.24 x ( 200 / 169 ) 2 x ( 3.4 /500 ) = 0.00193 But not less than the area of steel required to reduce shrinkage and temperature effects in concrete. For moderate crack control the area of steel in the primary direction is 75% of 0.0035xbxD. That will result in Pcrack = 0.75 x 0.0035 x 200 / 169 = 0.0031 ( which governs ) For one meter width strip of the slab: Ast = 0.0031 x 1000 x 200 = 621 mm2/m

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Adopt N16 @ 300 c/c spacing resulting in 667 mm2/m Moment capacity of the chosen area of steel is as the following: dn = 500 x 667 / ( 0.85 x 0.85 x 1000 x 32 ) = 14.42 mm Concrete force = 14.42 x 0.85 x 0.85 x 1000 x 32 = 333.5 kN  Фuo = 0.8 x 500 x 667 x ( 169 – (0.85 x 14.2/2)) = 43.5 kN.m/m For the full the width of the column Фuo ≈ 87 kN.m > M- = 37 kN.m

6.2.4 Serviceability Check The deflection of the end span will be calculated and compared with the limit state value. The short-term serviceability load is: Load = G + ΨsQ = 6.09 + 0.7 x 1.5 = 7.14 kPa

Figure 6.4: bending moment diagram in column and middle strip.

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Assuming the design strip is behaving like a continuous beam, the following bending moment distribution factors are used:

Figure 6.5: serviceability bending moment distribution factors.

At the end column, -Ms = 7.14 x 4 x 3.582 / 16 = 22.87 kN.m At mid span, +Ms = 7.14 x 4 x 3.582 / 11 = 32.2 kN.m At the first interior column, -Ms = 7.14 x 4 x 3.582 / 10 = 35.4 kN.m For the column strip the bending moment values are presented in the figure below:

Figure 6.6: Bending moment diagram at serviceability.

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The effective second moment of area for the column strip calculations: The gross second moment of inertia is = Ig = 2000 x 2003/12 = 1333 x 106 mm4

Figure 6.7: Column strip section at mid-span. Percentage of tensile steel used is 0.3 % and assuming same area of steel used in compression. σcs = ( 2.5 x 0.003 – 0.8 x 0.003 ) x 200 x 103 x 700 x 10-6 / ( 1 + 50 x 0.003 ) = 0.62 MPa Mcr = 2000 x 2002/6 x ( 0.6 √32 – 0.62 ) = 37 kN.m Mcr = 44< -Ms = 35.4, thus the stiffness of the section is uncracked. Δs = 35802 x ( -22.8 x 106 + 10 x 32.2 x 106 - 35.2 x 106 ) / (96 x 30100 x 1333 x 106 ) = 0.88mm Long-term deflection load = 6.09 + 0.4 x 1.5 = 6.7 kPa Δs.sus = 6.7 x Δs / 7.14 = 0.825 mm Kcs = 2 – 1.2 = 0.8 (compressive reinforcement equal tensile reinforcement as found in practice) Δtot = Δs + Kcs x Δs.sus = 1.54mm Which less than the deflection limit for floors supporting masonry walls of Lo/600 = 5.96 mm  adopt floor slab thickness of 200mm and N16@300 c/c.

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6.3 Column Design 6.3.1 Column Analysis The axial load applied on each column is found through the calculating the tributary area on each column. The figure below, shows the tributary area system:

The biggest tributary area is 16m2. Therefore, the loading on the column is as the following: N* = 8 x 16 x 9.57 + ( 0.3x0.3x24x 8 x3 ) = 1277 kN

Assuming a column section of 300 x 300 reinforced with 3 N20 on each face.

Figure 6.8: Tributary area distribution for each column.

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6.3.1.2 Check for Slenderness Assume this is a braced column where Le = Ln Ln = 3000 – 200 = 2800 mm  Le = 2800mm r =0.3D = 0.3 x 0.3 = 0.09  Le /r = 2.8 /0.09 = 31.11

6.3.1.3 Calculate αs Minimum applied moment M1* = M2* = 0.05x D x N* = 19.17 kN.m

uo = ( 0.85x( 300 x 300 – 8 x ( 102x π )) x 32 + 500 x 8 x ( 102x π ) ) = 3636kN  N*/ (0.6 x Nuo ) = 0.585 > 0.15  αc = √ ( 2.25 -2.5 x N*/ (0.6 x uo )) = 0.886  αc x ( 38 – f’c /15 ) x ( 1 + M1*/ M2*) = 63.5 > 31.11  Le /r < αc x ( 38 – f’c /15 ) x ( 1 + M1*/ M2*) Column is stocky

6.3.2 Design Column under Mmax* and N* Calculate unbalanced moment according to flat slab system M*v = ( coefficient x Mo ) end span – ( coefficient x Mo ) internal span = (0.75 – 0.65) x 61.32 = 6.132 kN.m However, the minimum bending moment to be transferred (clause 6.10.4.5) is M*v = 0.06[ ( 1.2 x 6.09 + 0.75 x 1.5 ) x 4 x 3.582 - 1.2 x 6.09 x 4 x 3.582 ] = 3.45 kN.m M* = max ( 3.45, 6.1 , 19.7 ) =19.7 kN.m

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6.3.3 Construction of Column Interaction Diagram Point A: Plastic centroid dPC = (300x300x0.85x32x150 + 942.4x500x50 + 628.2x500x150 + 942.2x500x250)/ 3636 = 152.8 mm Point B: Calculating the balanced point (Ku = Kub) For grade 500 steel the balanced neutral axis factor Ku = 0.545,  Neutral axis dn = 0.545x250 = 136.25mm Cc = 0.85 x 0.826 x 32 x 136.25x 300 = 918.3 kN εsc,1 = 0.003 x ( 136.25 – 50 ) / 136.25= 0.0019 70.4 kN Shear wall steel: As a summary, the finalised steel design for all shear walls is as the following: 

N16@200 vertical bars each face.



N12@300 horizontal bars each face.

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6.5 Cross Laminated Timber 6.5.1 Floor Panel

6.5.1.1 Analysis Each panel is 4 x 8m long in plane. The panels are simply supported on the CLT walls. The total vertical imposed load on the floor is 9.57 kPa excluding the self-weight of the panel. Weight of the panel = 4 x 500 x 0.105x 9.8 /1000 = 2.06 kN/m Total load = 9.57 x 4 + 2.06 x 1.2 = 40.75 kN/m With K1 = 0.8 (Live load) thus critical load is 50.93 kN/m With dead load case only total load = 7.08 x 4 + 2.06 x 1.35 = 31.1 With K1 = 0.57 therefore, the critical load is 54.5 kN/m Dead load is more critical with a value of 31.1 kN/m Maximum moment at mid span of the panel = 31.1 x 42 / 8 = 62.2kN.m Maximum shear force at the edge of the panel = 31.1 x 4 /2 = 62.2kN Calculating of the True Effective Bending Stiffness (EIeff) According to the Shear Analogy Method:

Figure 6.13: CLT cross section layout.

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Find the location of the Neutral Axis Z E1A1 = E3A3 the neutral axis is in the centre at 52.5mm BA = (10500 x 1000 x 353 / 12) x 2 + 350 x 1000 x 353 /12 = 7.62 x1010 N.mm2 BB = 10500 x 1000 x 35 x 352 x 2 + 350 x 1000 x 35 x 0 = 9 x 1011 N.mm2 (EI)eff = 7.62 x1010 + 9 x 1011 = 9.765 x 1011 N.mm2 Ultimate moment capacity: φMu = 0.7 x 32 x (9.765 x 1011 / 10500) / (0.5 x 105 ) x 0.57 = 22.6 kN.m per meter x 4 = 90.5 > 62.2 kN.m

Figure 6.14: Internal forces in the CLT floor cross section.

6.5.1.2 Calculating the shear stiffness (GAeff) using mechanically jointed beam theory. a = 105 – 35/2 -35 /2 = 70mm h1 / 2 G1 b = h3 / 2 G3 b = 35 / ( 2 x 700 x 1000 ) = 2.5 x 10-5 h2 / 2 G2 b = 35 / (2 x 70 x 1000 ) = 2.5x10-4 (GA)eff = 702 / (2.5 x 10-5 x 2 + 2.5x10-4 ) = 16.33 x 106

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6.5.1.3 Calculate the shear capacity of the panel. γ1 = γ2 = 1 / ( 1+ ( π2 x 10500 x 35 x 1000 x 35 / ( 80002 x 70 x 1000))) = 0.9724 Longitudinal shear resistance VrL = 0.7 x 2.8 x 9.765 x 1011 x 1000 / ( 0.97 x 10500 x 35 x 1000 x 35 + 350 x 35 x 1000 x 0.5 x 17.5 ) = 152 kN per meter Rolling shear strength VrR = 0.7 x (2.8/10) x 9.765 x 1011 x 1000 / ( 0.97 x 10500 x 35 x 1000 x ( 35 – 17.5 )) = 31 kN per meter Vr = min (VrL , VrR ) = 31 kN per meter x 4 = 124 kN > 62.2 kN

6.5.2 Wall Design The following calculation is based on the same panel size presented in floor panel design. E05 = 0.5 x E = 0.5 x 10500 =5250 MPa Ieff = 93 x 106 mm4 g13 = 0.7 (pinned-pinned) L =3000 mm PE= π2 E05 x Ieff / (0.7 x 3000 )2 = 1092.7 kN However, the Canadian Handbook states that the shear deformation plays a major role in affecting the compressive resistance of walls. Therefore, shear deformation is accounted for in the following formula: PE,v = PE / ( 1 + κ PE / (GA)eff ) Where κ is the shear coefficient factor equal 1.2 PE,v = 1092.7 / ( 1 + 1.2x 1092.7 /16.33 x 106) = 1092.6 kN Finding compressive capacity with accordance to AS1720:

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φNu = φ x Fc x Aeff = 0.7 x 22 x 35 x 2 x 1000 = 1078 kN Compressive capacity φNu = min ( 1078 ,1092.6 ) = 1078 kN Adjusted compressive capacity equal to φNu x K12 x K1 ρc = 1.03 S3 = g13 x L /1000 = 0.7 x 3000 /105 = 20 (105 mm is the wall thickness without the sacrificial layers) ρc x S3 = 20.6 Since ρc x S3 = 20.6 >20 ,then K12 = 200 / (ρc x S3 )2 = 0.47 K1 = 0.57 φNu = 1078 x 0.57 x 0.47 = 289 kN per meter According to ETABS output the highest compressive load on CLT walls in the ground floor was 569.5 kN for 10m wall, therefore the force is 56.97 per meter. φNu = 289 >>56.97 kN.

6.5.3 Fire Rating Design The fire rating design is based on a capacity of 90/90/90 minutes. The design includes both floor panels and CLT panels. The rate of char for CLT is 0.65mm /min. dchar = 0.65 x 90 = 58.5 mm ( roughly two layers )

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Therefore, the remaining depth is Dchar = D – dchar = 175 – 58.5 = 116.5mm dheat = 10 mm for floor and 16 mm for walls Dfire = Dchar – dheat = 116.5- 10 = 106.5 for slabs = 116.5 -16 = 100.5mm

Figure 6.15: Effect of 90min of fire exposure on the CLT section.

6.5.4 Connection Design As mentioned in Chapter 3, CLT has various connection configuration. This section will look at the design between floor-floor, wall-floor connections.

6.5.4.1 Floor-to-floor panel connection The force developed inside the floor due to bending must be safely transferred between the slab panels. The internal moment in the panel result in a compression tension couple that is transferred through the floor panel in the form of longitudinal shear. The moment applied on the floor panel is 22.6 kN.m per meter run. The compressive and tension forces applied on the panel is equal to 22.6/ 87.5 x1000 = 258.3 kN per meter run. The maximum applied shear force between the panels is 76.3 kN.

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Lap joint design example: CLT is 1175mm thick with 5 layers only. ρk = 500 kg/m3 Screws used are manufactured in Europe by Wurth Assy VG plus, having 8mm diameter and 160mm deep. The screws are placed at 45o inclined into the CLT floors and double crossed. Nominal diameter Head diameter Core diameter (d2) yield moment of the scew My,Rk Total length Ls crew Threaded length Ltr

8 10.2 5 16.7 N.mm 160 149

Table 6.4: Screw specifications

Spacing and edge distance of the screw are calculated with accordance with Z-9.1-614 from DIBT. a1 = 5 d = 5 x 8 = 40mm a2 = 1.5 d = 1.5 x 8 = 12mm a2,c = 3 d = 3 x 8 = 24mm Minimum width of the horizontal joint = 2 x 24 + 12 = 60mm It is advantageous to place the centre of gravity of the screw at the timber joint. Therefore, the screw shall be placed equally in the top and bottom member of the lap. Hence, the screw needs to penetrate by length/( 2√2 ) = 52mm measured vertically from the centre of the screw. This depth equal to a real screw length of 52x √2 = 74mm The characteristic point side withdrawal of the screw is calculated in the following table.

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CLT

Thickness Screw

layer

vertical

penetration

Screw

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penetration

(parallel to screw α

Fax,α,RK

axis)

mm L1

35

20

28.284

45

3879

C1

35

35

35.000

90

5600

L2/1

35

35

49.497

45

6788

Joint

0

L2/2

35

35

41.133

45

6027

C2

35

35

39.150

90

5871

L3

35

20

23.504

45

3444

216.569

16267

Table 6.5: characteristic withdrawal strength calculation sheets. Therefore, Fax,RK = 16.26 kN Design withdrawal strength is Fax,Rd = Fax,RK x 0.9 / 1.3 = 11.26 kN Spacing S = 40x √2 = 56mm, adopt 100 mm spacing Design shear capacity: Fv.Rd = 2 x ( 2x 11.26x1000 / (√2 x 100 ) )= 318.4 kN/m >258.3 kN

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6.5.4.2 Wall to floor connection Shear force applied from the slab on the wall is equal to 15.6kN per meter. This shear force acts as withdrawal force on the nail connecting the floor to the wall. Therefore the capacity of the connection must be compared to 15.6 kN per meter run.

Figure 6.16: Various geometry of screws supplied in the market. Check the capacity of screwed joints with 8mm diameter and spacing of 200mm. Using JD4 timber, Qk is determined from Table 4.6 (B) in AS1720.1 to be 104 N. For a spacing of 200mm, the number of screws in a meter would be 5 screws. According to Table 2.2 and using screws for primary structural elements in structures other than houses, the φ factor is equal to 0.8. According to Table 4.3(A), K17 for n =5 is 0.94. Using Tx40 nails (250 length and 75 mm penetration into the wall) The withdrawal capacity of the joint is as the following: Nd.j = 0.8 x 0.94 x 75 x 5 x 104 /1000 = 29.3 kN per meter > 15.6 kN withdrawal force.

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Figure 6.17: Floor to wall connection geometry.

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6.6 Raft Foundations In general, when buildings are design on shallow ground with low bearing capacity it becomes more economical to design a raft foundation than isolated pad footings. The reason behind such philosophy is that the sizes of the pad footings will over-lap due to their large dimensions. Moreover, each pad footing will cause high concentrated bearing pressure on the soil, while in the case of a raft foundation, the pressure is distributed on a large surface area. Therefore, a solid reinforced rigid concrete slab is far more economical than traditional pad footings. In the structural view, a raft slab acts as a flat plate or a flat slab upside down, that is due to the pressure coming from the soil bearing on the bottom of the slab causing mid-span bending to be upward and vice-versa for the negative bending. Generally, the raft foundation will develop the maximum available bearing under the building. However, in case of very high buildings, even this large bearing capacity is not sufficient to resist. As a result of such case, deep foundations are employed such as deep piles. Another advantage aspect in using a raft foundation is that due to its continuity and rigidity, differential settlements are greatly reduced in comparison with individual column pads. The design of raft foundations may be done by one of the two approaches: 

The finite element method, using computer programs such as SAFE and STAAD foundation. (most popular method)



The traditional manual rigid method.

The advantage of the rigid method that is very simple to use and can be easily applied using hand calculations. However, this method is kind of limited to a regular grid of columns. On the other hand, the finite element method is highly accurate and can be employed for any shape of rafts and irregular grid of columns, even cores and shear walls. Commercially available computer program can easily handle the analysis. However, ones should know the basis of the design.

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Figure 6.18: Typical raft slab configuration.

6.6.1 Traditional Rigid Method The conventional rigid method assumes the following two conditions: 1. The mat is behaving as an infinitely rigid foundation, and as a result of such behaviour, the differential flexural deflection of the mat does not influence the pressure distribution under the foundation. 2. The soil pressure is acting as plane surface or a straight line, this assumption is placed to ensure that the pressure centre coincide with the centre of load distribution of the mat as shown in figure ( ).

Figure 6.19: Raft slab load balancing.

6.6.1.1 Design Process The raft foundation shown in figure () has dimensions of BxL. The loads applied on the foundation through the columns are indicated as P1, P2, P3, … etc. The design

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steps of the raft slab using the conventional rigid method could be summarised as the following: Step 1: Check soil pressure against allowable bearing capacity

Figure 6.20: Applied loads on the structure. The summation of the columns working loads is: = 43578 kN Following the assumption that the slab is rigid, the soil pressure under the slab can be found using the traditional stress equitation as the following:

Where A = area of the raft ( B x L ) = 20x20 = 400 m2

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Ix = moment of inertia of the raft about the x-axis = B L3 /12 = 20x203/12 = 13.3x106 Iy = moment of inertia of the raft about the x-axis = L B3 /12 = 20x203/12 = 13.3x106 Mx = moment of the applied loads about the x-axis = Ptotal ey + Mx (lateral load) My = moment of the applied loads about the y-axis = Ptotal ex + My (lateral load) Where ex and ey are the measured eccentricities from the centre of gravity of the raft. The coordinates of the load local eccentricities are given by the following term:

X'= (4x[956+1270+843+872+1408+970]+6x[1451+1266]+8x[1028+1281+1556+1060]+ 10x[1585+2086]+12x[1028+1281+1543+1048]+14x[1048+1452]+16x[956+1270+8 42+842+1395+ 9710]+20x[629+970+1366+1370+970+632])/ 43578= 9.881m Where x1, x2, x3 are the X-coordinates of the loads. = 9.881-20/2 = -0.119m

Y' = (4x[970+1270+1281+1281+1270+970]+8x[1366+843+1451+2086+1452+842+1370 ]+12x[ 1445+872+1266+1585+1048+842+1366]+16x[969+1408+1556+1543+1395+970]+ 20x[

628+970+1060+1048+971+629])/43578 = 9.56m

Where y1, y2, y3 are the Y-coordinates of the loads. 𝐿 ey = Y ‘ – 2 = 9.56-10 = -0.44m

Compare the bearing pressure at any point under the slab with the bearing capacity of the soil. Mx = Ptotal ey + Mx (lateral load) = 43578x(-0.44)+9 = -19183 kN.m

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My = Ptotal ex + My (lateral load) = 43578x(-0.119) = -5185.8 kN.m 𝑃 43578 = = 109 𝑘𝑁/𝑚2 𝐴 400 Soil pressure at different points is as the following:

𝜎 = 109 −

19183 5185.8 𝑥− 𝑦 = 109 − 1.44𝑥 − 0.39𝑦 13333 13333

Soil pressure at various locations in the raft:

A-1 A-6 B-1 B-6 C-1 C-6 D-1 D-6 E-1 E-6 F-1 F-6 G-1 G-6 H-1 H-6 I-1 I-6 stress 91 99 96 104 99 107 102 110 105 113 108 116 111 119 114 122 120 127 Table 6.6: loads applied on the design strip.

The soil pressure on the centreline of the strip is assumed to be constant and its value is calculated as the average of both strip ends. The average soil pressure under the design strips is presented in the following table: Strip Average pressure

A

B

C

D

E

F

G

H

I

94 100 103 106 109 112 115 118 123

Table 6.7: Average soil pressure under the design strip.

The total soil reaction on each strip is calculated using the following formula: Rstrip-B= qarg x B x L = 100x3x21.4 = 6420kN The total applied loads on Strip B is the sum of the forces coming through the columns, which would be: PB = 956 + 1270 + 843 + 872 + 1408 + 970 = 6319 kN

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However, to achieve static equilibrium, the point loads coming from the columns should balance with the total soil reaction. To achieve this condition, the point loads must be modified. This is achieved by averaging the point loads and the soil pressure. Pavg = (Rstrip-B + PB)/ 2 The modified soil pressure would be : qmod = Pavg / L The modified columns’ load are obtained by multiplying the loads by a factor α: Where α = Pavg / PB The new modified loads on the strips are presented in the diagram below:

Figure 6.21: Load balancing on the design strip.

The strip was modelled in Microstran as a beam with the loads shown above and the following results were obtained:

Figure 6.22: Bending moment diagram. Obtained from Microstran.

Figure 6.23: Shear force diagram. Obtained from Microstran.

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6.6.1.2 Design for flexure The bending moment used in the design is calculated by dividing M* by the width of the strip to obtain the moment per meter run. M'=M/B Thus the bending moment used in the design are as the following: M+ = 482kN.m/3 = 160.6kN.m M- = 332/3 = 110.6kN.m Designing the raft foundation depth The depth of the slab is controlled by the punching shear check on an exterior column. Shear strength of the concrete assuming a 700mm depth is Фvuo =Ф udom (0.34√f’c ) Where dom is the average depth around the critical shear perimeter u is the length of the critical shear perimeter = 2(X+ dom/2)+2(Y+ dom/2) = 2x(300+ 625/2) + 2x(300 + 625/2) = 2450mm ; X and Y are the column dimension. And Ф is the shear reduction factor = 0.7 Therefore Фvuo = 0.7 x 2450 x 625 x ( 0.34 √32 ) = 2061.5 kN The applied shear force is equal to 1556 kN < 2061.5 the design ratio is 1556/ 2061.5 = 0.75 700mm depth is adequate to resist punching shear.

6.6.1.3 Flexural reinforcement design According to AS3600-2009 clause 9.1.1.a, defines the minimum area of reinforcement to be the following term: Р = 0.24 (D/d)2 f'ct.f / fsy for flat plates.

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As a result of the above term, the minimum reinforcement to be placed is 1277.3mm2/m or N20@240. The highest bending moment applied is 160.6 kN.m/m  using the simplified formula Ast = Mu / (370 d) = 160.6x106 / (370x 625) = 695 mm2/m AS3600-2009 imposes a maximum spacing of bars to control crack. The spacing “s” is the minimum of 250 or D. the minimum spacing required to satisfy this requirement is 250. Moreover, the standards imposed minimum area of steel to control cracks depending on the degree of crack control needed. In this situation where the slab appearance is not important, a minimum degree of crack control is imposed. st = 1.75xbxD = 1.75x1000x700 = 1225mm2/m After comparing all the previously calculated areas of steel. The minimum area of steel required is 1277.2mm2/m, which result in N20@240 or 1292mm2/m Check moment capacity dn = Ast x fsy / ( 0.85 x ϒ x f'c x 1000 ) = 1227.2 x 500 / ( 0.85 x 0.85 x 32 x 1000 ) = 26.5mm εst = ( d – dn )/ dn x 0.003 = ( 625 – 26.5 ) / 26.5 x 0.003 = 0.067 > 0.0025 Steel yields  Фuo = 0.8 x 500 x 1292 x ( 625 – ( 26.5/2 )) = 316.15 kN.m > 160.6 kN

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Chapter 7: Financial Plan

Researched by: Omar El Hawat Written by: Omar El Hawat

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7.1 Financial Plan The construction industry is rapidly expanding and there is a high demand for high rise buildings to support the growing world’s population. However, construction and developing companies are seeking new technology and advancements that will improve the structural performance of the building as well as reduce any costs in construction. The main factors that will affect the profit when delivering the project are the need of labourers and the overall time for construction as well as completing the project. If these factors are reduced, they will significantly increase the project’s overall profit margins. A potential material that can increase productivity and reduce construction costs is Cross Laminated Timber (CLT). Cross-Laminated Timber is becoming increasingly popular in Europe as it poses as a better alternative to traditional materials such as steel, concrete and masonry. Earlier in this report, we have discussed the structural design and performance of Cross-Laminated Timber and concrete; hence, we have designed an Eight Storey building out of both materials. In this chapter, we will be comparing the overall efficiency and benefits of using these two materials for the eight storey model of the building. This will be done by comparing the overall construction process, the time frame of the construction project, the amount of labour needed, and the cost of materials. After the comparison is made there will be recommendations and conclusions towards Cross laminated timber and its use as a new material for construction in residential and commercial industries. Note: The Pictures used in this report are for illustrative purposes and do not represent the actual project.

Figure 7.1: Cross-laminated Multi-Dwelling building in New Zealand

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7.2 Construction sequence The buildings made of both Concrete and CLT will have very similar construction processes especially in the initial and closing stages of the project. However, due to the use of different materials, there will be a need for different construction methods that will affect the construction duration and cost of the project. To better understand this, the construction sequence for both buildings made from different materials will be discussed in this section of the report.

7.2.1 Access to Construction site One of the most essential factors to consider in construction is to have good site access. The site needs to be well set out and well planned for the delivery of materials and onsite storage. The construction site should adopt an office for all workers and visitors to report to. This enhances workplace safety in an organised manner. The construction site should also include a pathway for trucks to safely enter and exit without disturbing traffic on public roads. It should also account for storage of materials and equipment/ machinery that are delivered onsite.

Figure 7.2: Establishing Access to sight for workers and machinery

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7.2.2 Construction Set out It is crucial that the construction of the buildings is carried out with accurate construction methods and in adherence to the structural plans and Australian standards. To do this efficiently and correctly, a surveyor is required to perform a construction survey and lay out markings for the contractors and builders to work from. Construction works cannot be commenced before this stage. The marks and pegs that the surveyor lays out represent a certain RL (reduced level) and position on the site. These are used by contractors to carry out Excavation works so that they are able to know exactly how deep to excavate, in order to place the concrete and CLT members at the correct RL.

Figure 7.3: Shows a surveyor using a total station to set out marks for the construction set out.

7.2.3 Excavation and compaction Once the construction set out has been marked by surveyors, the contractors are then able to carry out excavation works. The markings will give the contractors an indication of where to excavate and by how much to excavate. Since the foundation

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of the buildings is a raft slab, it requires minimal excavation at approximately 0.30.5m deep. Excavation is carried out in an efficient manner so that earth material is collected efficiently and quickly. Once excavation is complete and the ground is levelled out, the soil is then compacted to around 95% to ensure its bearing capacity is sufficient for the placement of the foundation. The compaction is an important aspect before construction, as it will reduce any long-term settlement that may occur to the soil after a long period of time. The compaction of the soil will strengthen the foundation. Moreover, compaction is required to support the proposed buildings, as they will carry a substantial load.

Figure 7.4: Excavation works being carried out

7.2.4 Raft Slab Construction The raft slab is a simple and very common type of foundation that will be used for the building. The support for both the concrete structure and the CLT building will be a concrete raft slab. Construction of this raft slab is very simple and requires little time to construct as well as skilled labourers. After the excavation has taken place, formworkers will set out the formwork of the required slab giving it a thickness and setting it to the necessary height using a level. Once this is complete, the steel fixers are able to place in the necessary reinforcement and hence concrete can then be poured. After

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concrete has been poured, the concrete is cured for 14 days before further construction on the slab is done. Cross-laminated timber is a much lighter material and produces small gravity loads. When comparing both structure, the gravity loads generated by the CLT building is 80% less compared to reinforced concrete. This will result in a much smaller foundation requiring a thinner raft slab.

Figure 7.5: Excavation works being carried out

7.2.5 Crane Installation A tower crane is required onsite for the construction of a multi dwelling building. It is used to lift heavy materials and equipment to their required location without the need of labourers which may prolong the duration of the project. The crane for the concrete building will be located at the elevator shaft. When constructing the raft slab, there will be a deep excavation for concrete pouring and placement of steel pedestals. Once concrete has been poured and cured, the crane can then be bolted tightly to the steel pedestals that are now embedded in the deep concrete structure. Once the foundation of the crane is secure, another mobile crane is required to erect the tower crane; hence,

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skilled labourers are needed to connect pieces of the crane together. This process takes 1- 2 days to complete and requires many workers to produce. Cross-Laminated timber is a light material and the construction of a CLT building will only require the tower crane to lift the panels and steel brackets. A tower crane may not be necessary for the construction of small buildings and a mobile crane can be used for basic cranage needs. However, a mobile crane can become more expensive with frequent use. For this reason, the construction of both high rises will require a tower crane to make the overall construction process more efficient.

Figure 7.6: Initial construction of crane, being attached to slab

7.2.6 Scaffolding around Building Scaffolding around the building is a temporary structure that is essential and provides workers with easy access to floors and allows them to work safely at heights. Both structures will require construction of scaffolding and is hired over the period of the construction. The construction process of the concrete building takes a long time because the construction of each level can’t commence until the concrete on the previous level has been fully poured and cured. This process normally requires 14 days. During this time

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frame, only minor works are to be completed; as a result the scaffolding is available but not being used to its total potential. Due to this, the construction process is prolonged and will require a higher cost of hiring the scaffolding.

Figure 7.7: Scaffolding around structure

7.2.8 Construction of Building

7.2.8.1 Concrete Structure The construction of the concrete building will require many processes and services. These services require skilled workers with proficient problem solving skills to complete the building. There are three main components in the structure that need to be built; these are the concrete columns, the concrete walls (Shear walls) and the concrete slabs. Each one of these components will involve several different skilled workers such as for the placement of formwork, instalment of steel reinforcement and pouring of concrete.

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Figure 7.8: Placement of formwork for the concrete columns which are ready to be poured.

7.2.8.2 Column Construction The first step in building the concrete column is the completion of the raft slab. Steel fixers will work out the positions of the columns and walls and place steel reinforcement that will stick out of the finished slab and point upwards. The steel fixers will then connect the existing reinforcement and tie it to new reinforcement bars and stirrups. When this is complete, formworkers will then place the Formwork that will mould the shape of the concrete column. However, before the concrete is poured the raft slab must be cured for a period of 14 days. This means that the construction of the column and pouring of concrete commences after the 14th day. This is to ensure that the concrete will reach its optimum design strength. The formwork for this project will be simple as they are square in shape and require plain plywood or steel in order to achieve the desired shape. There are a total of 28 columns on every floor which have the dimensions of 300mm by 300mm.

7.2.8.3 Wall Construction On each level of the concrete building, there will be nine shear walls. This will assist the building in resisting lateral loads and help decrease deflections. The construction of the shear walls are initiated at the same time as the construction of the columns. Likewise, with the construction of the columns, they are initially set out during the

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construction of the raft slab. Once starter bars are placed in the slab, steel fixers will then be able to finish the placement of the steel for the walls. The formworkers then place formwork in order to mould the shape and dimensions of the wall. This task may sound simple however it is important that the workers are skilled enough to accurately set out the locations of the walls as well as set out the correct dimensions for it. Each wall will have a dimension of 4m wide and 200mm thick. The formwork that is used for this task may consist of either plywood or steel. Steel formwork may be more expensive, however it is an easier option and requires less labour and skill to use.

Figure 7.9: Conventional steel formwork used to set out walls. which are ready to be poured.

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7.2.8.4 Slab Construction After the formwork and steel work has been constructed for the walls and columns, the process can be completed for the slabs and next floor. In order to construct the slab, the formwork is first required to be setup. In order for the formwork to support the weight of the workers and the poured slab, there will need to be sufficient falsework. Once the formwork and false-work has been set up, the steel fixers are then able to initiate their work; providing the bottom and top reinforcements for the slab and all other reinforcements that will provide the structure with shear strength and help resist punching shear. The thickness for the eight slabs of this building are to be 200mm. Additionally, the height between each slab is three meters.

Figure 7.10: The underside formwork and false work of the slabs in the concrete structure

7.2.8.5 Placement of concrete and curing It is highly convenient to pour all concrete members together in order to account for the time required for the concrete to attain its full strength (Curing time). The process of pouring concrete often involves a minimum of two trucks, a concrete agitator and a concrete pump truck to transport the concrete to its desired location. When pouring the concrete, skilled labourers are needed in order to compact the concrete to ensure that the finished product is durable and void free. When pouring the concrete, the columns and walls are filled in first and a vibrator is inserted to ensure that it has been compacted properly. After the walls and columns have been poured, the slab is then poured into place. Concreters are then required to screed the concrete and compact it to ensure that the finished product is produced to high quality and durability as well

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as giving the concrete a smooth finish. Once the concrete is poured, the process of curing the concrete will take place and this means that the construction process of the next floor will need to wait a minimum of 14 days. Workers however, can start to walk on the slab after only a few days.

Figure 7.11: Curing of concrete by spraying a chemical compound.

7.2.8.6 Repetition of construction until structure is complete After the first level, the construction process becomes repetitive and hence after curing is over of the remaining levels can be built. As the structure becomes higher and more levels are constructed, certain services will start to become more expensive. Such services will include the scaffolding around the building as more will need to be ordered and constructed onsite. Also, the concrete placement for the higher levels will become more difficult to place. In these situations a concrete crane pump is required.

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Figure 7.12: Concrete crane truck pumping concrete to the upper levels of the building.

7.2.9 Cross Laminated Structure The construction of Cross-laminated timber is quite simple and quick. This is because the cross-laminated timber will be manufactured in factories where measurements are taken and panels are manufactured to their intended design size. This means that when they are delivered onsite, the construction process is simple and little skill is required in connecting the Cross-laminated timber panels. For this reason the construction of the CLT building will only require four labourers; one of them being skilled in order to guide the others and read the plans to know the necessary procedures to connect the panels together. Also, each CLT structural element will have its own unique product number, which can be referred to on the structural drawings that show their exact position and installation procedures.

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Figure 7.13: manufacturing of CLT timber to the appropriate size and measurements.

7.2.9.1 Shear Wall Construction Even though this multi storey building will be constructed from Cross-Laminated timber; the structure will need to include a Concrete Shear core as it is required to resist wind loads and stabilise the building of any torsion and displacements. The Shear wall will be constructed immediately after the raft slab is completed. Since it is the only structure that needs to be concrete, the shear wall will adapt slip-form formwork which will allow it to be constructed immediately. It is possible to adopt this as the only load the shear wall is carrying is its own self-weight. The construction of the shear wall will be one storey ahead of the construction of the CLT wall panels and Slab floors. This will ensure that the slip form doesn’t interfere with the construction of the CLT Panels. Shear wall dimensions will be 3 meters tall and 200mm thick.

7.2.9.2 Installation of CLT Wall Panels After the raft slab foundation has been constructed for the Cross-Laminated timber building, and the Curing period of 14 days have passed; it is then that the installation of the CLT walls can begin. Before the completion of the Concrete raft slab, the labourers will be inserting steel connection plates which are embedded to the concrete.

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This will provide the connection between the CLT wall panels and the Concrete Raft slab. Basic cranage is required for the assembly of the walls. Labourers will then use the plan to guide the CLT wall panels and place them in their correct location. Once they are placed in their locations, the CLT wall panels are then properly secured into their positions with nails and steel plate connections. On every floor there are 20 CLT wall panels of the same thickness, which is 175mm. However, each panel will have its unique product number and reference in the design plan. They will also have different dimensions and window/ door cut outs.

Figure 7.14: Mobile crane moving the CLT wall panel will be nailed and secured into place..

7.2.9.3 Slab CLT panel Installation Immediately after the construction and placement of the CLT panel walls, the slabs can then be built into place. The floor slab of every level will be constructed 175mm thick. Again cranage is necessary to haul the slabs and be guided into place by labourers; ensuring that it is placed into its exact location and later secured into place. The slab is to come in several sheets and then be connected to together as shown in the figure below and secured together by planks that are nailed in the CLT timber.

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Figure 7.15: connection of CLT slab sheets

7.2.9.4 Connections of CLT One of the most important aspect of building with CLT is to ensure that the connections between the structural elements are secure and sufficiently installed. This is because if the connection is weak, then the structure will fail at the connection. The main materials in constructing CLT panels also include the steel plates, nails and connections. The connections for this structure will include connection between the wall panels and floor slab, wall panels and Concrete Raft slab, wall panels and panels, and between CLT Floor slabs.

Figure 7.16: connection between CLT column and Concrete Raft slab.

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Figure 7.17: connection between CLT wall panels using nail plates

7.2.9.5 Repetition of construction until structure is complete The process of constructing the remaining floors is simple and repetitive, basic cranage is required to haul the CLT structural elements and guide them to their exact locations by the labourers. As the building will get taller from construction of new levels, the prices of the services and methods of construction almost remain constant throughout the lifecycle of the project. However, the mobile crane will take longer to set up for taller structures; the overall construction of each floor will span no longer than a week.

P a g e 207


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Figure 7.18: Diagram shows the construction of a multistorey CLT building.

7.2.10 Installation of services (electricity and other works) Once the construction of the building has been completed, the services of the building can then be incorporated into the structure. Such services can include Electrical works, Painting, Cabinet installations, Tiling and plumbing works. Installation of services is quicker and easier in a CLT Structure as it is simple to drill and cut through the timber; this may lead to achieving cheaper quotes and receiving quicker delivery of service.

7.2.11 Closure: Finished Product Once the Structure has been constructed, and services have been provided for the building, the structure is then ready to be occupied and completed. At the closure of the building, a few days is required to take down the scaffolding around the building and to remove the crane from the site.

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7.3 Duration of construction After discussing the construction sequence of the Concrete and CLT buildings, a further break down of the construction stages is needed to assess the duration required to complete the project. The main construction stages are broken down to even smaller processes and subtasks. We will then research by contacting developers and contractors for a reasonable time to complete each task of the process.

The

construction of the project was assumed to be carried out on a five day working period per week. The duration will be compared in the tables below: Note: All the prices and durations mentioned in this report were advised by multiple different companies and project managers as well as comparing these prices with the Rawlinson Australian Construction Handbook.

7.3.1 Concrete Structure The Construction process and methodology was researched in books and by consulting with experienced project managers about the length and duration of each construction process

1

Task Name

Duration

Start

Finish

Surveying

1 day

Mon 2/02/15

Mon

Predecessors

2/02/15 2

Construction

1 day

Tue 3/02/15

Tue 3/02/15

1

Set-out 3

Site Access

2 days

Wed 4/02/15

Thu 5/02/15 2

4

excavations

2 days

Fri 6/02/15

Mon

3

9/02/15 5

Floor level -1 1 day

Mon 12/10/09

Mon 12/10/09

6

Raft Slab

P a g e 209

Chapter 7: Financial Plan Task Name 7

-

Form

Duration

Start

Finish

Predecessors

1 day

Tue 10/02/15

Tue

4

10/02/15

work 8

-

Steel

1 day

Tue 10/02/15

-

Concr 0.5 days

Wed 11/02/15

-

Curin

4

Wed

7,8

11/02/15

ete 10

Tue 10/02/15

Work 9

Capstone B

14 days

Wed 11/02/15

Tue 3/03/15

9

1 day

Wed 11/02/15

Thu

9

g 11

Crane Construction

12

Scaffolding

12/02/15 1 day

Wed 11/02/15

Thu

9

12/02/15 13

Columns

14

-

Form

1 day

Tue 3/03/15

-

Steel

1 day

Tue 3/03/15

17

-

Form

1 day

Tue 3/03/15

-

Steel

Scaffolding

Wed

1 day

Tue 3/03/15

Wed

12,10

4/03/15 1 day

Tue 3/03/15

Wed 4/03/15

P a g e 210

12,10

4/03/15

Work 19

12,10

Shear Walls

work 18

Wed 4/03/15

Work 16

12,10

4/03/15

work 15

Wed

12,10


Floor level -2

21

Floor Slab

22

-

Form

Capstone B

Duration

Start

Finish

Predecessors

1 day

Wed 4/03/15

Thu 5/03/15 14,15,17,18

1 day

Wed 4/03/15

Thu 5/03/15 14,15,17,18

Thu 5/03/15

Thu 5/03/15 23

Fri 6/03/15

Wed

work 23

-

Steel Work

24

-

Concr 0.5 days ete

25

-

Curin

14 days

25/03/15

g 26

Columns

27

-

Form

1 day

Thu 26/03/15

-

Steel

1 day

Thu 26/03/15

30

-

Form

1 day

Thu 26/03/15

25

-

Steel

Scaffolding

Thu

25

26/03/15 1 day

Thu 26/03/15

Thu

25

26/03/15

Work 32

Thu

Shear Walls

work 31

25

26/03/15

Work 29

Thu 26/03/15

work 28

24

1 day

Thu 26/03/15

Thu

25

26/03/15 33

Floor level -3

34

Floor Slab

P a g e 211


-

Form

Capstone B

Duration

Start

Finish

1 day

Fri 27/03/15

Fri 27/03/15 27,28,30,31,3 2

work 36

-

Steel

1 day

Fri 27/03/15

Fri 27/03/15 27,28,30,31,3 2

Work 37

-

Concr 0.5 days

Mon 30/03/15

-

Curin

Mon

35,36

30/03/15

ete 38

Predecessors

14 days

Mon 30/03/15

Fri 17/04/15 37

1 day

Fri 17/04/15

Mon

g 39

Columns

40

-

Form

20/04/15

work 41

-

Steel

1 day

Fri 17/04/15

43

-

Form

1 day

Fri 17/04/15

-

Steel

Scaffolding

Mon

38

20/04/15 1 day

Fri 17/04/15

Mon

38

20/04/15

Work 45

38

Shear Walls

work 44

Mon 20/04/15

Work 42

38

1 day

Fri 17/04/15

Mon

38

20/04/15 46

Floor level -4

47

Floor Slab

48

-

Form work

P a g e 212

1 day

Mon 20/04/15

Tue

40,41,43,44,4

21/04/15

5


-

Steel

Duration

Start

Finish

Predecessors

1 day

Mon 20/04/15

Tue

40,41,43,44,4

21/04/15

5

Tue

48,49

Work 50

-

Concr 0.5 days

Tue 21/04/15

21/04/15

ete 51

-

Curin

14 days

Wed 22/04/15

Columns

53

-

Form

1 day

Tue 12/05/15

-

Steel

1 day

Tue 12/05/15

56

-

Form

1 day

Tue 12/05/15

Tue

51

-

Steel

Scaffolding

Tue

51

12/05/15 1 day

Tue 12/05/15

Tue

51

12/05/15

Work 58

51

Shear Walls

work 57

Tue

12/05/15

Work 55

50

12/05/15

work 54

Mon 11/05/15

g 52

Capstone B

1 day

Tue 12/05/15

Tue

51

12/05/15 59

Floor level -5

60

Floor Slab

61

-

Form

1 day

Wed 13/05/15

work 62

-

Steel Work

1 day

Wed 13/05/15

Wed

53,54,56,57,5

13/05/15

8

Wed

53,54,56,57,5

13/05/15

8

P a g e 213


-

Duration

Concr 0.5 days

Start

Finish

Predecessors

Thu 14/05/15

Thu

62,61

14/05/15

ete 64

-

Curin

14 days

Thu 14/05/15

Columns

66

-

Form

Wed

63

3/06/15

g 65

Capstone B

1 day

Wed 3/06/15

Thu 4/06/15 64

1 day

Wed 3/06/15

Thu 4/06/15 64

1 day

Wed 3/06/15

Thu 4/06/15 64

1 day

Wed 3/06/15

Thu 4/06/15 64

1 day

Wed 3/06/15

Thu 4/06/15 64

1 day

Thu 4/06/15

Fri 5/06/15

work 67

-

Steel Work

68 69

Shear Walls -

Form work

70

-

Steel Work

71

Scaffolding

72

Floor level -6

73

Floor Slab

74

-

Form

1

work 75

-

Steel

1 day

Thu 4/06/15

Fri 5/06/15

-

Concr 0.5 days ete

P a g e 214

66,67,69,70,7 1

Work 76

66,67,69,70,7

Fri 5/06/15

Fri 5/06/15

74,75


-

Curin

Duration

Start

Finish

Predecessors

14 days

Mon 8/06/15

Thu

76

25/06/15

g 78

Columns

79

-

Form

Capstone B

1 day

Fri 26/06/15

Fri 26/06/15 77

1 day

Fri 26/06/15

Fri 26/06/15 77

1 day

Fri 26/06/15

Fri 26/06/15 77

1 day

Fri 26/06/15

Fri 26/06/15 77

1 day

Fri 26/06/15

Fri 26/06/15 77

1 day

Mon 29/06/15

Mon

79,80,82,83,8

29/06/15

4

Mon

79,80,82,83,8

29/06/15

4

Tue

87,88

work 80

-

Steel Work

81 82

Shear Walls -

Form work

83

-

Steel Work

84

Scaffolding

85

Floor level -7

86

Floor Slab

87

-

Form work

88

-

Steel

1 day

Mon 29/06/15

Work 89

-

Concr 0.5 days

Tue 30/06/15

30/06/15

ete 90

-

Curin g

91

14 days

Tue 30/06/15

Mon

89

20/07/15

Columns

P a g e 215


-

Form

Duration

Start

Finish

Predecessors

1 day

Mon 20/07/15

Tue

90

21/07/15

work 93

-

Steel

1 day

Mon 20/07/15

95

-

Form

1 day

Mon 20/07/15

-

Steel

Scaffolding

Tue

90

21/07/15 1 day

Mon 20/07/15

Tue

90

21/07/15

Work 97

90

Shear Walls

work 96

Tue 21/07/15

Work 94

Capstone B

1 day

Mon 20/07/15

Tue

90

21/07/15 98

Floor level -8

99

Floor Slab

100

-

Form

1 day

Tue 21/07/15

work 101

-

Steel

1 day

Tue 21/07/15

Work 102

-

Concr 0.5 days

Wed 22/07/15

-

Curin

14 days

Thu 23/07/15

Removal

P a g e 216

22/07/15

7

Wed

92,93,95,96,9

22/07/15

7

Wed

100,101

Tue

102

11/08/15

g 104 Crane

92,93,95,96,9

22/07/15

ete 103

Wed

1 day

Wed 12/08/15

Wed 12/08/15

103

Chapter 7: Financial Plan Task Name 105 Scaffolding

Capstone B

Duration

Start

Finish

Predecessors

2 days

Thu 13/08/15

Fri 14/08/15 104

Removal

Table 7.1: Detailed breakdown structure

As can be seen from the Breakdown structure of the project, if commencement is on the second of February; the project will be completed 14th of August. The duration of the project is estimated to be completed after 28 weeks. This is assuming that there would be no delays due to weather uncertainties or any delay from delivery of materials or absent workers.

7.3.2 Cross Laminated Structure The Construction process and methodology was researched through previous projects that have used CLT as a building material. Also Consultation of experienced project managers and their advice has been incorporated in the work breakdown structure shown below.

1

2

3

4

Task Name

Duration Start

Finish

Surveying

1 day

Mon

Mon

2/02/15

2/02/15

Tue

Tue

3/02/15

3/02/15

Wed

Thu

4/02/15

5/02/15

Fri 6/02/15

Mon

Construction Set out

Site Access

excavations

1 day

2 days

2 days

Predecessors

1

2

3

9/02/15 5

Floor level -1

6

Raft Slab

P a g e 217


7

8

9

Capstone B

Task Name

Duration Start

Finish

Predecessors

Formwork

1 day

Tue

Tue

4

10/02/15

10/02/15

Tue

Tue

10/02/15

10/02/15

Wed

Wed

11/02/15

11/02/15

Wed

Tue

11/02/15

3/03/15

Wed

Thu

11/02/15

12/02/15

Mon

Mon

12/10/09

12/10/09

Tue

Tue

3/03/15

3/03/15

Tue

Tue

13/10/09

13/10/09

Tue

Thu

3/03/15

5/03/15

Tue

Wed

3/03/15

4/03/15

Thu

Mon

5/03/15

9/03/15

Steel Work

Concrete

10 Curing

11 Crane Construction

12 CLT Construction

1 day

0.5 days

14 days

1 day

1 day

4

7,8

9

9

13 Elevator Shaft (Shear wall) 14 Formwork/ Setup

15 Concrete

16 Wall construction

17 Scaffolding 1

0.5 days

1 day

2 days

1 day

10

12

10

10

18 Floor level -2 19 Slab Floor 2

P a g e 218

2 days

16,17

Chapter 7: Financial Plan Task Name 20 Wall construction

Capstone B

Duration Start

Finish

Predecessors

2 days

Mon

Wed

19

9/03/15

11/03/15

Wed

Thu

4/03/15

5/03/15

Mon

Tue

9/03/15

10/03/15

Wed

Fri

11/03/15

13/03/15

Fri

Mon

13/03/15

16/03/15

Tue

Wed

10/03/15

11/03/15

Fri

Mon

13/03/15

16/03/15

Mon

Wed

16/03/15

18/03/15

Wed

Fri

18/03/15

20/03/15

21 Elevator Shaft (Shear wall) 22 Concrete

23 Scaffolding 1

1 day

1 day

17

19



2 days

1 day

23,20

25


29 Scaffolding 1

1 day

1 day

23

25



2 days

2 days

29,26

31

P a g e 219

Chapter 7: Financial Plan Task Name

Capstone B

Duration Start

Finish

Predecessors

1 day

Mon

Tue

29

16/03/15

17/03/15

Wed

Thu

18/03/15

19/03/15

Fri

Tue

20/03/15

24/03/15

Tue

Thu

24/03/15

26/03/15

Thu

Fri

19/03/15

20/03/15

Tue

Wed

24/03/15

25/03/15

Thu

Mon

26/03/15

30/03/15

Mon

Wed

30/03/15

1/04/15


35 Scaffolding 1

1 day

31



2 days

2 days

35,32

37


41 Scaffolding 1

1 day

1 day

35

37



45 Elevator Shaft (Shear wall)

P a g e 220

2 days

2 days

41,38

43

Chapter 7: Financial Plan Task Name 46 Concrete

47 Scaffolding 1

Capstone B

Duration Start

Finish

Predecessors

1 day

Wed

Thu

41

25/03/15

26/03/15

Mon

Tue

30/03/15

31/03/15

Wed

Fri 3/04/15

47,44

Tue

49

1 day

43


2 days

1/04/15 50 Wall construction

2 days

Fri 3/04/15

7/04/15 51 Elevator Shaft (Shear wall) 52 Concrete

53 Scaffolding 1

1 day

1 day

Tue

Wed

31/03/15

1/04/15

Fri 3/04/15

Mon

47

49

6/04/15 54 Floor level -8 55 Slab Floor 8

56 Crane Removal

57 Scaffolding Removal

2 days

1 day

2 days

Tue

Thu

7/04/15

9/04/15

Thu

Fri

9/04/15

10/04/15

Thu

Mon

9/04/15

13/04/15

53,50

55

55

Table 7.2: Detailed breakdown structure of CLT building

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Capstone B

After referring to the work breakdown structure for the construction of the CrossLaminated Building, it can be seen that if the project commences in the 2nd of February, the project is expected to finish by the 10th of April. This means the project would have been completed in 10 weeks. This is with the assumption that there would be no delays by the weather and that there are no delays from workers and transportation of materials. As can be seen from the comparison of both buildings, the construction of the concrete building which has a duration of 28 weeks is almost three times longer than the construction of the Cross- Laminated Timber building which has a duration of only 10 weeks. This will not only mean that the project will be delivered earlier, but this will also cut costs on labour and any hiring services that are onsite. These durations will be used as a reference to estimate the cost of service and labour required for the completion of each.

7.4. Cost of Labour and Services The construction of the two buildings requires different materials and hence different workers to complete their tasks. Some roles require skilled labourers where as other tasks can be completed using generic and cheaper labourers. The tasks and labourers required will be assessed and analysed to make a cost effective analysis on both buildings this will be used to determine which material is easier to construct with and most cost effective.

7.4.1 Services There are multiple services that are involved in the construction of both buildings and will charge complex rates based on the duration and type of work required to be carried out. Such services will include construction methods and resources that are necessary onsite in order to carry out the works.

7.4.2 Crane Tower A service that is required to be used for the construction of the Concrete and CLT building is the Crane tower. It is used to hoist heavy materials and transport them to their required and necessary locations. This service requires the installation of the crane which requires a few trained labourers and transportation of the crane to the site

P a g e 222


Capstone B

using multiple trucks. Another factor that will affect the price of the service is the height of the crane. In addition to this price, there will need to be an operator that is an additional cost for hiring the crane. After referring to Rawlinson’s Australian Construction Handbook 2015 edition and consulting with multiple companies, the findings for the cost of this service are listed in the table below. When referring to the work breakdown structure, it can be seen that the Crane is operational only 20 weeks of the duration of the project and hence cost of labour and petrol have been based on this.

Crane Hire

Cost

Over 28weeks

Favco 500 Crane Hire

$2000/ week

$56, 000

Initial Construction

$4000

$4000

Diesel Fuel

$150/week

$3000

Operator

$45/hr (7hr day)

$6300

Servicing

$500/3Months

$1000

Crane Removal

$4000

$4000

Total

$74, 300

Table 7.3: Estimated cost of hiring Favco 500 Crane for the construction of Concrete building

Crane Hire

Cost

Over 10weeks

Favco 500 Crane Hire

$2000/ week

$20, 000

Initial Construction

$4000

$4000

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Capstone B

Diesel Fuel

$150/week

$1500

Operator

$45/hr (7hr day)

$3150

Servicing

$500/3Months

$1000

Crane Removal

$4000

$4000

Total

$33, 650

Table 7.4: Estimated cost of hiring Favco 500 Crane for the construction of CLT building

7.4.3 Scaffolding The Scaffolding is hired on monthly bases and when needed as the construction stage progresses and more levels are built. The Cost analysis is shown in the diagram below. The cost of scaffolding depends on two main factors, the amount of labourers required to complete the installation, and also the size of the job in m3. After calling multiple Scaffolding hire companies, it was found that the cost of hire for the first month of scaffolding per floor with area of 130m2 was around $1000 for the first week and $100 for the remaining weeks of hire. For the removal of the Scaffolding there was an additional $500 cost per square metre area of 130m2. Construction Stage

Duration

of Area

Total Cost

Hire

Required

Level 1

24

130m2

$3300

Level 2

21

130m2

$3000

Level 3

18

130m2

$2700

Level 4

15

130m2

$2400

Level 5

12

130m2

$2100

P a g e 224


Capstone B

Level 6

9

130m2

$1800

Level 7

6

130m2

$1500

Level 8

3

130m2

$1200

Cost of $4000 removal Total Cost

$22, 000

Table 7.5: Estimated cost of hiring Scaffolding

Construction Stage

Duration of Hire

Area Required Total Cost

Level 1

8

130m2

$1700

Level 2

7

130m2

$1600

Level 3

6

130m2

$1500

Level 4

5

130m2

$1400

Level 5

4

130m2

$1300

Level 6

3

130m2

$1200

Level 7

2

130m2

$1100

Level 8

1

130m2

$1000

Cost of removal $4000 Total Cost

$13, 800

Table 7.6: Estimated cost of hiring Scaffolding for CLT

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Capstone B

When comparing the prices of the scaffolding required for both buildings, it can be seen that there is a significant cost reduction with the scaffolding due to the decrease in hire time.

7.4.4 Required Labourers Onsite With the construction of multi-storey buildings, there is a high demand for skilled labourers and tradesmen that are required to complete certain tasks. The majority of the budget will be spent on labour; it is important to adopt methods and construction methodologies that will reduce the amount of labour needed for construction. The necessary labour required for the construction of the project will be calculated and displayed below.

7.4.4.1 Concrete Structure The main type of labourers required is displayed in the table below with their average wages per hour of hire. Cost per hr Concrete Pourer and Sourer

$70/hr

Form-worker

$70/hr

Steel Fixer

$70/hr

Table 7.7: Average rate of hire for labourers

For the construction of the concrete building, it was estimated that all labourers worked an eight hour day. Additionally, four workers were required to work on installing and setting up the formwork while four steel workers were required to install the steel reinforcements. When the concrete is poured, there will be four concreters will be present to compact the concrete and screed it to the required finish. Therefore, for the duration of the whole project, the Cost of the following Labourers is listed in the table below:

P a g e 226


Capstone B

Total Hours

Overall cost over project

and 320

$ 22,400

Form-worker

704

$ 49,280

Steel Fixer

704

$ 49,280

Total Cost of Labour

$120,960

Concrete

Pourer

Sourer

Table 7.8: Estimated total labour costs for concrete

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Capstone B

7.4.4.2 Cross-Laminated Timber Structure With the construction of the Cross-laminated timber, there are no requirements for highly skilled labourers except for the installation of the shear wall. The main labourers required for this construction are mentioned in the table below: Cost per hr Concrete Pourer and Sourer

$70/hr

Form-worker

$70/hr

Steel Fixer

$70/hr

General Assembly Labourers

$40/hr

Table 7.9: Average rate of hire for labourers in CLT

With the formation of the shear wall, only two form-workers and two steel fixers will assist in the construction of the shear wall and will be working 4 hour days. Also two Concrete labourers are required for the construction of the shear wall and will also work 4hr days. However, for the remaining construction of the Cross laminated building, there will be only 4 general labourers required to place the CLT wall and slab panels in place and to securely connect them together.

P a g e 228


Capstone B

Total Hours

Overall cost over project

and 32

$2240

Form-worker

36

$2520

Steel Fixer

36

$2520

General Labourers

224

$8960

Total Cost of Labour

$16,240

Concrete

Pourer

Sourer

Table 7.10: Estimated total labour costs for the construction of the CLT building After comparing the cost required for Labour for both the construction of the Concrete Building and the construction of the Cross-laminated building; it can be seen that there is a significant reduction in the cost of labour from $120,960 reduced to $16,240 by using CLT timber. This is due to two main reasons, the reduction of construction time means that labourers are hired for a lesser time and hence labour hire costs are reduced significantly. Also because the skill required to install CLT panels are not as demanding as form working and steel fixing, The cost of their wages are reduced.

7.5 Cost of materials The total cost in materials will be compared for the construction of both the Crosslaminated building and the Reinforced Concrete building. Both buildings require different materials for the process of construction. Also some materials will need to be delivered and shipped from overseas. These expenses will be included and considered in this cost analysis for the two buildings. Prices were obtained from the Rawlinson Construction Handbook and consulting through different manufacturers to get a reasonable price in today’s market. The prices that were obtained are provided in the table below:

P a g e 229

Chapter 7: Financial Plan Material

Cost

Concrete

$250 / m3

Steel

$1850 /tone

Plywood

$40 / m3

CLT timber

$1400 / m3

Capstone B

Table 7.11: Average rate of cost for the materials

The cost of materials will be measured by first calculating the volume of materials in each and every floor and then converted to tonnes to determine the total cost.

7.5.1 Concrete Structure The construction of the concrete multistorey structure will require multiple materials to be ordered and delivered to site. These materials basically compose of Concrete, Steel reinforcement, and the formwork needed to be used to mould the concrete. For this analysis, the cost of materials required for each and every storey will be compared in the table below: The cost of these materials has been compared with multiple Major suppliers within NSW.

P a g e 230


Volume (m3)

Capstone B

Quantity per

Levels

Total Volume(m3)

floor Concrete -

Walls

2.40

9

8

172.8 m3

-

Columns

0.27

28

8

60.48 m3

-

Slab

73.6

1

8

588.8 m3

-

Raft Slab 200

1

1

200 m3

Total

1022.1 m3

Cost

$255,520

Steel -

Walls

0.05

9

8

3,6 m3

-

Columns

0.0054

28

8

1.21 m3

-

Slab

1.5

1

8

12 m3

-

Raft Slab 4.0

1

1

4.0 m3

-

Total

20.81 m3

-

Cost

$300,282

Formwork (Plywood) -

Walls

0.048

9

8

3.456 m3

-

Columns

0.072

25

8

14.4 m3

-

Slab

23.36

1

8

186.9 m3

-

Raft Slab 0.8

1

1

0.8 m3

Total

205.53 m3

-

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Volume (m3)

Capstone B

Quantity per

Levels

Volume(m3)

floor -

Total

Cost

$8,221

Table 7.12: Estimated cost of all the materials

The Total Price for the materials required to construct the Concrete Building is calculated as the total volume of materials used multiplied with their rates. The total material cost was estimated to be $564,022.

7.5.2 Cross Laminated Structure The Construction of the Cross Laminated Structure still requires the materials of concrete and steel to build the shear walls of the building, however its used in much less quantities. However, the majority of the building will be constructed of CLT with the use of metal plates as well as self-tapping screws. The table below shows the cost of the concrete, construction of the building:

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Material

Capstone B

Quantity per

Levels

Total Volume(m3)

floor Concrete -

Walls

2.40

7

8

134.4 m3

-

Raft Slab 120

1

1

120 m3

Total

254.4m3

Cost

$63,600

7

8

2.8 m3

1

1

2.4 m3

-

Total

5.2 m3

-

Cost

$75,036

7

8

2.68 m3

1

1

0.48 m3

-

Total

3.168 m3

-

Cost

$126

Steel -

Walls

-

Raft Slab 2.4

0.05

Formwork (Plywood) -

Walls

-

Raft Slab 0.48

0.048

Table 7.13: Estimated concrete and steel costs for CLT

The total cost required for the concrete Component is $138,762. For the cost of the CLT timber panels, they will incur and additional cost for shipping as they will be transported from New Zealand. It is estimated that it would cost $20 extra per cubic meter hence the cost of CLT per cubic meter is increased.

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Volume (m3)

Capstone B

Quantity per

Levels

Total Volume(m3)

floor Cross-Laminated Timber -

Walls

69.3

1

8

554.4 m3

-

Slab

64.4

1

8

515.2 m3

Total

1069.6 m3

Cost

$1,497,400

Table 7.14: Estimated CLT costs for the construction of the CLT building In addition to this cost, there will be excessive amounts of self-tapping screws and Angle brackets that will need to be ordered. The cost of the entire structure is determined in the Table below. Material

Cost per 100

Quantity

Total

5000

$2,500

30, 000

$3,000

Total

$5,500

items Steel

Brackets

and $50

Quality

Self- $10

framing High

Tapping Screws

Table 7.15: Estimated costs for the Steel brackets and self-tapping screws The total cost of materials that are required to build the Cross- Laminated Timber Building is $1,641,662. When compared to the cost of materials required to construct the concrete, it can be seen that the cost of materials for the Cross-Laminated building is much more than the price of concrete. This could be due to the reason that the total embedded energy required to produce these materials are significantly reduced with the production of Timber.

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7.6 Advantages and Disadvantages of Using CLT Cross-laminated Timber is becoming increasingly popular in the construction industry within Europe, Canada and North America. This is because Cross-Laminated timber has many advantages to offer. However, Cross-Laminated Timber as a construction material is relatively new and has limited performance history. In this section of the report, the Advantages of Cross-laminated Timber as well as its disadvantages will be assessed.

7.6.1 Advantages Cross-Laminated timber has many advantages to offer in comparison to traditional constructing methods hence why it gained popularity with some companies. Some of these Advantages are listed below: 

Promotes Safer Construction:

Constructing using CLT timber gives a better/ safer overall working environment when compared to traditional methods of construction. This is because there is a significant reduction in dust, noise, and vibrations which causes less overall disruptions to the surrounding community. Also working with CLT reduces and eliminates the injuries that are associated with formworking and steel-fixing. In addition to that, the construction of CLT structures is much faster than any other method. Therefore the workers will have a reduced period of work time and hence further reduce the possibility of any injuries. 

Sustainability:

Using CLT as a building material offers better thermal performance as it promotes better air tightness which reduces the need for cooling machinery such air conditions. Also, timber is a carbon neutral structural option as 1m³ of timber stores 0.25t of carbon. CLT offers little to no waste and significantly reduces the need of fresh water consumption when compared to Concrete. Using CLT is more sustainable as it reduces the deliveries to the site. Most of the materials are delivered in the initiation of the project.

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Capstone B

Light Weight Material:

Due to the fact that CLT is a light material, there are many advantages that come from this. It requires basic cranage and hence a small crane is able to lift the material. This will reduce costs with shipping and transportation costs as a smaller truck is required. In addition, a lighter material will help promote better handling of the material and hence less supervision is required and higher quality can be obtained when installing CLT panels. Having a lighter weight material offers great structural design advantages. CLT being almost 80% lighter than traditional construction material, will reduce the overall deadweight that is being applied to the structure. This will in turn allow for the design of smaller members and design of smaller foundation. 

Cost Effective Material:

One of the most influential aspects of constructing with Cross-Laminated timber is the fact that there are great cost reductions when compared to construction using Concrete and Steel Structures. There are many reasons for this as outlined in the earlier sections of the Financial Plan. For one, there is a great reduction in the length of construction and hence this will reduce the labour costs and the hire length of services that are required to stay onsite. Moreover, with the construction of CLT buildings, there is no need for skilled labourers such as form-workers and steelworkers as it is fairly simple to connect and assemble. Nevertheless, the price of the CLT material is much higher when compared with the price of concrete and this may balance out the costs of labour.

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7.6.2 Disadvantages CLT is new to the industry and has very little research behind it. For this reason there are quite a few disadvantages in using this material which are listed below: 

CLT is not manufactured in Australia: Because CLT is a relatively new building material, it has not yet been manufactured in Australia and hence they can only be bought from overseas manufacturers in places such as New Zealand and Europe. This means that it will take longer to deliver the product and hence the cost of material will increase due to the extra cost in shipping.



There are no Australian Standards for CLT: Because CLT is a new material, there has not yet been Australian standards developed for Cross-laminated timber. This means that structural designs of buildings will need to be obtained from a different country. Alternatively, the designs would need to comply with the standards used in other countries such as Europe and North America. Additionally, if material fails due to poor quality assurance from the manufacturer, they cannot be sued due to the fact there are no codes.



Customer preferences: Many people view a structure that is constructed from CLT to be weak, hazardous and unsafe; especially in construction of High-rise buildings. People may be under the impression that timber will weaken over time with rain and that timber will light on fire much quicker than concrete and can potentially bring down the building.



Long Shipping time: When constructing using Cross-Laminated Timber, The materials will need to be ordered and shipped in early to ensure that the project is not delayed. However it is likely that some manufacturers will make errors that will result in missing and incorrect quantities. In instances like these the project may be further delayed by several months depending from where the materials where ordered from.

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Capstone B

Limited long term performance history: CLT is a new building material that has been around no longer than a decade, hence project managers and builders are reluctant to use this material as uncertainties/ problems in the material’s serviceability properties may arise. As a result, they are more willing to construct with concrete as a safer and more reliable means of construction.

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7.7 Comparison between CLT and Concrete Cross-laminated timber is becoming increasingly popular in the construction industry in countries such as Europe and Canada. Cross-laminated timber has been used as a building material not only for small dwellings, but is now being used with multi storey buildings. However, Cross laminated timber is a material that is new and has limited performance history. Therefore, many project managers and developers are hesitant to implement this material in the construction industry without having a sound Knowledge of its benefits and advantages. Concrete has been used for many decades and has proved to be a reliable and suitable building material for all building types. It can be designed to withstand many different loads and producing certain shapes is possible with the use of special formwork. Concrete had replaced other conventional materials such as steel and timber structures as it proved to be cheaper to produce and provided many structural, construction and durability benefits. In contrast, resource materials that are used to produce concrete are now depleting and cost of concrete is increasing. Therefore, it is important to assess new building materials that can be a potential substitute for concrete and other conventional building materials. In this section, the Cross-Laminated timber will be assessed and compared to traditional concrete as a structural and construction material in multi storey buildings. The main aspects that will be compared is the structural advantages, cost of construction, and its environmental impact.

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7.7.1 Time of Construction Earlier in this report is the construction process and sequence for both the Crosslaminated building and the concrete building. After comparing the sequential construction of both buildings through research and consulting with many project managers, by asking their advice; it was estimated that the construction of the concrete multi storey building was much longer than the construction of the Cross-Laminated building. Cross-laminated timber and concrete are compared with the construction of an eight storey high building. It was found that the construction of the concrete building was estimated to be 28 weeks long whereas the construction of the Cross laminated building was estimated to take only 10 weeks to complete construction. The reason behind this is that the construction process of the concrete building take much longer than the construction of the cross-laminated timber was because once concrete was poured, the concrete needs to be cured for a minimum of 14 days before the second layer can be constructed and poured. This is due to various reasons, for one, if the concrete is loaded before its cured may not reach its required strength to hold the load and hence supporting false work will need to remain in place until the concrete has acquired sufficient strength. The cross-laminated timber structure is easy to construct hence requires only a few days to construct each level. Each Cross-Laminated timber panel will come with a unique identification number which relates back to the construction plans and shows how each panel is meant to be installed and assembled. Once the CLT panels are placed in their correct positions, they are secured using steel brackets and self-tapping screws. This leads to the construction of each floor taking no longer than a week to construct. In addition when delivering a project, it is much quicker to finish constructing a project when using the material

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Capstone B

Materials used for Construction fo building

Time of Construction for Eight storey building

Concrete

Cross-Laminated Timber

0

5

10

15

20

25

30

Weeks

Figure 7.19: Comparison of the time of construction of the eight storey building for both Cross-laminated timber and Concrete.

7.7.2 Labour and service hire Labour When constructing the multistorey building, there are several workers that are required to be onsite to make the construction process possible. However, due to construction of eight storey building using two different materials, they require different methods of construction and therefore different skilled workers to make this possible. As discussed in previous sections of this report, the construction of the concrete building requires many different skilled workers and process in order to correctly place the concrete and ensure that it is constructed with the correct reinforcement and dimensions in order to hold the necessary weight. In order to do this correctly, there is a number of different skilled workers required to construct this, such as the formworkers, the steel fixers and the concreters. For the construction of the concrete building, most days will require up to eight workers in order to construct the formwork and steel work alone. The rate of pay that is required to be paid for these skilled workers is much higher than the rate of pay that is paid for the general labourers. The result of this is the concrete material can prove costly to use for the construction of the building.

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The construction of the Cross laminated building is simple and easy. The installation of the CLT panels only requires general labourers with one leader that is able to read the plans and effectively assemble the panels to create the building. On average the construction of the CLT building will only require four generic labourers in order to assemble the CLT panels together. However, for the construction of the concrete footing and the concrete elevator shaft (Shear walls), they will need to be done by skilled labourers that will carry out the construction process properly. These workers such as steel fixers, formworkers and concreters are much higher paid than the generic workers. However, these workers have limited responsibility when constructing the building. When comparing the construction of the Concrete and CLT building in terms or Labour hire, the concrete building will require mainly high skilled workers to carry out construction work and will need to pay for more workers over a longer span of construction span. The construction of the Cross-laminated timber building on the other hand, will require a larger range of workers. However, the majority of the work will be conducted by the generic labourers who have a lower rate of pay. A detailed analysis comparing the total cost being paid to labourers for both the construction of the concrete and CLT building are discussed in the financial assessment of the report. The graph below shows the total cost of labour hire that is required for the construction of the concrete and CLT building.

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Capstone B

Cost of Labour $120,000 $100,000 $80,000 $60,000 $40,000 $20,000 $0 Concrete

CLT

Form workers ($70/hr)

Steel-Fixers ($70/hr)

Concrete Pourers ($70/hr)

Generic Labourers ($40/hr)

Figure 7.20: Comparison for the cost of labour When referring to the figure above, it can be seen that the cost of labour for the construction of the concrete building is significantly higher than the construction of the CLT building. This is because of two main reasons. The first reason, is the duration of construction for the Concrete building is 18 weeks longer, and hence will require the labourers to work onsite for much longer hours for the duration of the project. In addition to this, the majority of the construction of the concrete building will require more skilled labourers than generic labourers and hence results in excessively higher costs when compared to the construction of the CLT structure. Service: The construction of a multi storey building will require many services in order to make the construction process much more feasible and efficient. Two services that will be common with the construction for both Concrete and Cross-laminated timber building are the hire of Scaffolding and hire of Tower cranes. Both these services are charged depending on the amount of time they are required to stay onsite. In the previous section of this report its price was calculated for the construction of the eight storey building. The findings are displayed in the graph below.

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Capstone B

Service Hire 80000

70000 60000 50000 40000 30000 20000 10000 0 Crane Hire

Scaffoldig Hire

Concrete

CLT

Figure 7.21: Comparison for the cost of services After comparing the cost of service hire for both materials, it can be seen that there is a significant reduction in the cost of services for the CLT building. This is mainly due to the reduced construction time of the building.

7.7.3 Structural advantages Smaller members When comparing Cross-laminated timber with concrete for the construction of multistorey building, CLT has many structural advantages which make it a potential building material in the construction industry. CLT has a relatively low density of 500kg/m3 when compared to concrete which has 2400kg/m3. Concrete is almost five times heavier which means the generated dead load of the structure will be higher. Therefore, each individual member will be carrying a bigger load and hence will require a bigger size. When designing the concrete building, the size of the walls and slab were both 200mm thick. However, the thickness of the CLT panels for both walls and slabs ended up becoming 175mm thick. This means that the concrete building requires more volume than the CLT building. This will result in more material to be bought and will result in a much higher construction costs for the building.

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Capstone B Density

Concrete

2400 kg/m3

Cross-Laminated Timber

500 kg/m3

Table 7.16: Density of CLT and Concrete

Smaller Foundation The decreased member sizes also offer other structural benefits to the building. Due to the weight of the building being decreased significantly, material used is decreased substantially. Additionally, the total volume of material, the total deadweight of the building the foundation size are decreased. The foundation of the raft slab used in the design of the concrete building was 500mm deep. However, the foundation of the CLT building was 300mm which will result in smaller costs due to smaller purchases of materials.

7.7.4 Cost of materials For the construction of an eight storey building there are many components that must be purchased. The materials will differ for the construction of the Cross-Laminated timber and concrete building. The materials required for the Concrete structure mainly comprise of Concrete, steel reinforcement and plywood. Whereas the construction of the Cross-Laminated building will comprise mainly of cross-laminated timber, Steel bracket connections, and self-tapping screws. The cross-laminated structure will also consist of concrete components and also require formwork, reinforced steel and plywood.

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Chapter 7: Financial Plan `

Cost

Concrete

$250 / m3

Steel

$1850 /tone

Plywood

$40 / m3

CLT timber

$1400/ m3

Capstone B

Figure 7.17: Average rates/cost of the main materials

Cost of Materials for Concrete Building 350000 300000 250000 200000 150000 100000 50000 0 Concrete

Steel

Plywood

Figure 7.22: The total estimated cost of the materials

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Capstone B

Cost of Materials for CLT Building 1600000 1400000 1200000

1000000 800000 600000 400000 200000 0 Concrete

Steel

Plywood

CLT

Steel Angle Self-Tapping brackets Screws

Figure 7.23: The total estimated cost of the materials When comparing these graphs it can be seen that the overall cost of materials required for the construction of the Concrete building are significantly lower than the materials used for the CLT building. This is because the materials for the Cross-laminated timber is much more expensive than concrete and steel. This resulted in the cost of materials being more than doubled.

7.7.5 Transportation of material For the construction of the multistorey Concrete and Cross-Laminated Timber building, they required different materials and processes for delivery. The concrete is manufactured at a concrete plant in accordance with the specified plan which indicates its mixture ratio and required strength. It is usually manufactured locally and only called to site when the formwork and reinforcement have been completed and inspected by engineers. The delivery of concrete is inexpensive for short distances and normally included with the cost of material.

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Capstone B

For the construction of the CLT building, the manufacture of Cross-laminated Timber is not done locally and hence CLT will need to be ordered from other countries. Some suppliers and manufacturers include Canada, Europe and New Zealand. There are risks that are associated with the transport of these materials over large distances and hence may make it inconvenient to use. The shipment of the material may take a month or more, thus, the materials will need to be ordered quite early in the construction process in order to carry out the construction in the preferred time duration. Problems that can arise from shipping the materials from overseas is that the materials will need to have high quality assurance. It is possible for the manufacturers to make errors and send off incorrect or damaged items. This will result in a delay in the overall project duration which can prove to be very costly with the hire of services such as the crane and scaffold hire. This increases the risk of using CLT as the project could be potentially delayed. In addition, the CLT would be delivered over a large distance from overseas, the cost of delivery will increase the cost of material. Hence the use of concrete is much safer and reliable to use as it can be produced and delivered locally with little risk involved.

7.7.6 Prefabrication of materials The construction of the concrete multistorey building has a number of processes that are required to properly construct the concrete members in place. Such processes involves properly securing and setting up the formwork to the correct dimensions and placing the steel reinforcement in its correct location. On the other hand, when it comes to producing complex shapes and architectural designs for buildings, the level of skill required to construct the concrete member’s increases significantly. This makes it much more expensive to construct due to the shape and size of the required formwork. Pre-cast concrete members can be constructed within warehouses and controlled environments which makes it much easier to construct. However, this process is also an expensive option as it is heavy to transport and requires curing for 28 days. With the construction of a CLT building, complex designs are easier to manage as all the CLT panels will be manufactured to the specified dimensions with the correct specifications as shown in the structural plans. This makes it an easier material to construct with and eliminates the need of hiring any skilled workers in order to proceed

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Capstone B

with construction works. Also, CLT is easy to transport on trucks as they are 80% lighter than concrete and don’t require the same size trucks that would be used to deliver precast concrete panels. CLT is much easier to construct with as it is a lighter material to transport and complex shapes can be produced directly by the manufacturer.

7.7.7 Australian standards Concrete has been widely used in many buildings especially with the construction of high-rise buildings. These structures are designed with Australian standards which set specific requirements when designing structures to ensure that a structure is built to withstand extreme loading conditions. There are many structural firms and software in Australia that incorporate the Australian standards in order to design concrete members. Since, Cross-laminated is an innovative new material, there has not yet been any Australian standards produced for the design and manufacture of CLT. This means that if a building in Australia is to be produced and designed from CLT, the building will need to be designed using overseas standards such as Canadian Standards, North American Standards and European standards. This can cause many inconveniences for the developer of the building as any communication between the designer, architect and developer is distant. Moreover, any uncertainties or issues with the designed plans can be troublesome to solve especially once construction of the building has commenced. In addition, since there are no Standards for CLT in Australia, it is crucial that quality assurance is provided for the materials that are being bought. The reason behind this is that if the product fails, the manufacturer cannot be sued for damages in Australia as there are no standards for CLT.

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Capstone B

7.7.8 Environmental aspects Concrete is produced from the mixture of Cement, Fresh water and Fine and Coarse aggregates and produces different properties depending on the design mix. All three of these mixtures contribute to negative effects that are applied on the environment. Concrete requires the use of freshwater that is clean and free from particles which can affect the durability of the concrete. Since, concrete is used worldwide, enormous amounts of freshwater is required to be used which is becoming an environmental concern. Concrete also requires the use of coarse and fine aggregates which are acquired from natural sources in the environment. However, in Australia fine aggregates such as sand have become a depleting resource due to the increase in production in concrete. This has led to the development of artificial aggregates as an environmental measure to reserve natural resources. In addition, to these environmental concerns, production of cement is one of the biggest emissions of carbon dioxide gasses and is responsible for 5-7% of total emissions produced around the world.

Figure 7.24: Shows the percentage of CO2 emissions.

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Despite all the environmental aspects concrete is associated with the use of cement. Using CLT is a more environmentally friendly material that addresses these issues. Firstly timber is a renewable resource that can be farmed in forests and monitored for efficient production. Timber filters out the carbon dioxide gasses from the atmosphere and stores it inside the timber. In addition, the production of CLT produces little to no waste and also significantly reduces the need for freshwater consumption when compared to production of concrete. Using CLT as a building material offers better thermal performance as it promotes better air tightness which reduces the need for cooling machinery such air conditions. CLT is a more sustainable material as it reduces the deliveries made to the site because most of the materials are delivered in the initiation of the project.

7.7.9 Safety The construction of the multi storey building whether it is made from Cross-laminated timber, or concrete has structural components. In regards to the concrete buildings, they include produced and constructed onsite member. Whereas the components of the CLT building are manufactured in factories. This significantly reduces both the time the workers are onsite and also eliminates the hazards that are associated with placing the formwork and steel fixing aspect of the job. This allows the work environment to be much safer for all the workers. Also, with the construction of the CLT building, the panels are manufactured offsite and hence the workers will only need to assemble the panels in their correct positions and secure them so that they are structurally stable. This will result in a significant reduction in dust, noise, and vibrations which causes less overall disruptions to the surrounding community. Building with CLT gives a better/safer overall working environment when compared to traditional methods of construction as the workers will have a reduced period of work time and hence further reduce the possibility of any injuries.

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7.7.10 Durability The species that are used in CLT production are commonly softwood which is of low natural durability. When it is used in exposed application, it is recommended to not directly expose the particular panel to the exterior conditions. Typically, CLT buildings consist of either a skin of masonry or commercial facade material for instance fibre cement or aluminium. It is preferable that a cladding of naturally durable wood or a suitably preserved treated wood product should be utilised. Termite resistance The timber utilised in CLT is not reformed during the manufacturing process. As a result, the termite resistance performance is thought to be the same as ordinary timber. If the situation does require termite protection, then the building must be well protected in accordance to AS3660 Termite Management. Weather Protection Normally due to the rapid production time of CLT based systems, the short period of exposure of CLT to weather conditions does not remain an issue. Short periods and occasional exposure to rainwater will not have long-term effects on CLT. During construction, wall elements can be protected by using vapour barriers. Additionally, the building’s scaffolding can be wrapped to provide protection. Further strategies can be employed such as a coating system for the construction period only. However, long term exposure of CLT to weather conditions is not recommended.

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7.8 Summary of Results After comparing the construction of the Cross-laminated structure with that of the Concrete structure it was evident that CLT offered a much more expensive building solution when compared with traditional reinforced concrete. However, this is due to the fact that the price of CLT, is substantially higher than the cost of materials required for Concrete construction. The graph below shows the cost summary for the construction of both materials.

Comparison of the construction costs of both buildings 1800000 1600000 1400000 1200000 1000000 800000 600000

400000 200000 0 Concrete Labour

CLT Cost of Material

Services

Figure 7.25: Shows the Comparison of the costs associated with the construction of the CLT and concrete multistorey building. After comparing the costs associated with the construction of both buildings, the estimated total cost of constructing the building using Concrete reached $781, 282. However, the total estimated cost of the building when using CLT was $1,705, 352. These estimates are purely towards the construction of the buildings. The estimates are expected to vary in reality because real projects are more complex and delays are likely; these will in turn increase the total cost of the project. However, the assumptions that were used to price the construction of the buildings were consistent for both the concrete and CLT building; hence the cost estimates obtained show an accurate representation of their relative costs. When compared it can be seen that by using CLT as a substitute to traditional concrete, the total cost is 55% more expensive

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than traditional concrete. These results are viewed as a big disadvantage in the developer’s perspective. However, CLT provides many advantages such as delivering the project sooner and relying on less workers to complete the project as the construction labour is substantially decreased. CLT has a better effect on the environment as it is a renewable resource that filters out CO2 from the atmosphere. Once CLT becomes cheaper, it will be more feasible and economical to build with as the costs in services and labour are significantly lower.

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Capstone B

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Conclusion and recommendations Throughout the duration of this project, we have attempted to research the structural and economic feasibility of the building materials, Concrete and Cross-laminated Timber. This research was conducted by comparing the construction and design of two identical multistorey buildings made from the above mentioned materials. This was initiated by researching the design and material properties of CLT and concrete in order to further understand their potential as building materials as well as how they can be efficiently engaged and integrated into the structure. In addition to this, the design of the multistorey structures provides many challenges and complexities. To overcome these challenges, further research needs to be conducted to increase the rigidity and stability of the building, which hence leads to the implementation of more rigid systems such as the shear wall-frame system. Once this was completed, we had the sufficient knowledge and information to carry out the design of the building. This was completed through learning and using SAFE and ETABS to analyse and design the components of the building with both materials. In addition to this, we also learnt how to design using CLT with both European and Canadian standards and thereafter compared our results with what was achieved using the design software. After the design was completed for both buildings and the member sizes for all structural components were determined; a financial analysis was carried out to determine the efficiency of constructing with both materials and therefore determine whether CLT has potential to enter the building industry. The results and comparison that were obtained throughout the report will be stated in the body of this concluded.

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Structural The light weight and high stiffness of timber allows for thinner members to be implemented. The CLT building was analysed to resist extreme wind loading conditions in addition to its own weight, super imposed dead loads and live loads. As a result, it was concluded that three layer panels totalling 105mm thickness are sufficient to meet the strength limit state design. However, it should be noted that the deflection of CLT panels was not discussed in this paper; if calculated, it is approximately 500 mm, however the span could be easily halved resulting in a 30 mm deflection. Additionally, the purpose of the report was to maximise the span by pushing the limits of CLT to the extreme. According to the Building code of Australia, both buildings must achieve a minimum FRL fire rating of 90 minutes. For CLT, achieving this exposure was resulted by designing an additional two sacrificial layers increasing panel thickness to 175 mm. However, a more common approach is to add two layers of 16mm thickness plaster board; each adding an extra 30 minutes to the fire rating. Moreover, a more efficient fire system could be implemented such as sprinklers that can allow the structural engineer to push back the size of panels to three layers. In summary, CLT is a valid alternative to ordinary reinforced concrete structures.

Construction After comparing the construction costs of the concrete building and the construction of the Cross-laminated structure, it was found that CLT has many benefits to offer and proves to have high potential in the construction industry. When comparing the construction duration of the project, it is evident that the construction of the CLT building takes almost a third of the time required to construct the concrete building. This allows the project to be delivered much quicker as well as reduce costs on labour and hiring services that are available onsite. Due to the fact that the construction period for the CLT building is much shorter than the concrete building, the labourers are working less hours on site and as a result the labour costs can be reduced. Also, the hiring of services such as Tower crane and Scaffolding are reduced with the shortened construction period, and hence only half as much is paid when constructing with Cross-laminated timber.

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An additional benefit is that the labourers required for the construction of the Crosslaminated building do not have to be skilled labourers as they only need to hoist the materials to their construction position. In contrast, the labourers required for the construction of the concrete building must be specifically skilled for installation of the formwork, installation of the steel work and pouring of the concrete. The skilled labourers are much more expensive than the general labourers and the latter only require minimal training in order to complete the task. However, when comparing the costs of the entire project for both the Concrete and CLT structures, it can be seen that the cost of CLT material is much more expensive than the cost of Concrete. Hence the total cost of the project increase, making it more expensive to build with CLT. Due to the fact that Cross-Laminated timber is a newly introduced building material, there are no available Australian standards or design codes for building with it. The Cross laminated building will therefore need to be designed using European Codes, North American codes or sent to overseas manufacturing companies to complete the design. However, this may cause inconveniences in communication between the design engineers and the project manager. Additionally, since the materials will need to be manufactured and shipped from overseas, there will need to be high quality measures put in place, as the shipping will take several weeks-to-months to arrive. If there are any damaged goods or missing items, it could possibly delay the project for months, hence there can be a high risk in using this product. Furthermore, since there are no codes in Australia, it is hard to ensure quality of the product because if it fails the suppliers cannot be sued. Cross-Laminated timber has high potential in the construction industry. Once there are sufficient design codes available for CLT, it is predicted that there could be a significant increase in its use for both residential housing and multistorey construction; provided that they are fire, weather and termite protected.

P a g e 258

Recommendations An important consideration, is that further research is needed to permit mainstream adoption of CLT in Australia. Once an in-depth study has been undertaken, and Australian standards have been written to provide guidelines and assurance for safety and effectiveness in CLT construction, the public may finally adopt it. More research is necessary regarding the building costs of the timber structure. Success of CLT construction in Australia requires competitive material cost, as well as efficient production costs which can only be obtained from research and learning. It is highly recommended that CLT should not be used as a sole building product, but as one in a system of materials. The use of steel and concrete with CLT will achieve a more cost effective and economic structure. This is present in our capstone, with concrete shear walls and raft slab.

P a g e 259

Researched by: Osman El-Zohbi

References

Written by: Osman El-Zohbi

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Page | 266

Appendix A- Model input

Figure A.1: Model initialisation tab in ETABS .

Figure A.2: Creating the grid for the model in ETABS .

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Figure A.3: Concrete material property input in ETABS .

Page | 268

Figure A.4: Concrete material strength input in ETABS .

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Figure A.5: Steel material property input in ETABS .

Figure A.6: Steel material strength input in ETABS . Page | 270

Figure A.7: Column cross section input to ETABS .

Figure A.8: Column property stiffness modification factors in ETABS .

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Figure A.9: Frame section property reinforcement data input into ETABS .

Page | 272

Figure A.10: Slab property data input to ETABS .

-

Figure A.11: Slab property stiffness modification factors input to ETABS .

Figure A.12: Wall property input to ETABS . P a g e | 273

Figure A.13: Wall property stiffness modification factors input to ETABS .

Figure A.14: Wind load factors input to ETABS .

Figure A.15: Ultimate load combinations input to ETABS .

Page | 274

Figure A.16: Strength reduction factors input to ETABS .

.

P a g e | 275

Appendix B – Model output

Figure B.1: Mxx at elevation A output from ETABS .

Page | 276

Figure B.2: Myy at elevation A output from ETABS .

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Figure B.3: Mxx at elevation B output from ETABS .

Page | 278

Figure B.4: Myy at elevation B output from ETABS .

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Figure B.5: Mxx at elevation C output from ETABS .

Page | 280

Figure B.6: Myy at elevation C output from ETABS .

.

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Figure B.7: Mxx at elevation D output from ETABS .

Page | 282

Figure B.8: Myy at elevation D output from ETABS .

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Figure B.9: Mxx at elevation E output from ETABS .

Page | 284

Figure B.10: Myy at elevation E output from ETABS .

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Figure B.11: Mxx at elevation F output from ETABS .

Page | 286

Figure B.12: Myy at elevation F output from ETABS .

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Figure B.13: Base axial force on the columns output from ETABS .

Page | 288

Figure B.14: My- in shear walls for 1.2G+1.5Q output from ETABS .

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Figure B.15: Mx in shear walls for 1.2G+0.4Q-Wy output form ETABS .

Page | 290

Figure B.16: Mx in shear walls 1.2G+0.4Q-Wx output from ETABS . output form ETABS .

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Figure B.17: Axial force in shear walls output from ETABS . output form ETABS .

Page | 292

Figure B.18: Column check and steel results output from ETABS . output form ETABS .

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Appendix C –Transfer slabs SAFE model output.

Figure C.1: Approximate defection of the cracked slab output from SAFE. output form ETABS .

Page | 294

Figure C.2: Slab forces/stresses control tab in SAFE. output form ETABS .

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Figure C.3: Slab moment intensities in the y-direction output from SAFE. output form ETABS .

Page | 296

Figure C.4: Slab moment intensities in the x-direction output from SAFE.

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Figure C.5: Slab top Reinforcement intensities in the y-direction output from SAFE. output form ETABS .

Page | 298

Figure C.6: Slab top Reinforcement intensities in the x-direction output from SAFE.

.

P a g e | 299

Figure C.7: Slab bottom Reinforcement intensities in the y-direction output from SAFE.

Page | 300

Figure C.8: Slab bottom Reinforcement intensities in the y-direction output from SAFE.

P a g e | 301

Figure C.9: Slab punching shear check output from SAFE.

Page | 302

Appendix D-CLT model input

Figure D.1: Material properties input to ETABS .

Figure D.2: Material properties strength input to ETABS .

P a g e | 303

Figure D.3: CLT floor panel input to ETABS .

Figure D.4: CLT wall panel input to ETABS

Page | 304

Appendix E- CLT model output

Figure E.1: CLT floor panel moment diagrams output form ETABS .

P a g e | 305

Figure E.2: CLT floor panel shear diagrams output form ETABS .

Page | 306

Figure E.3: Walls moment diagrams with 1.2G+1.5Q output form ETABS .

P a g e | 307

Figure E.4: Walls axial force with 1.2G+1.5Q output form ETABS . .

Page | 308

Figure E.5: Walls shear diagram with 1.2G+1.5Q output form ETABS .

P a g e | 309

Appendix F- RAFT Slab Input Data to SAFE

Figure F.1: Raft slab property data input to ETABS .

Figure F.2: Stiff plate property data input to ETABS .

Page | 310

Figure F.3: Soil subgrade property data input to ETABS .

P a g e | 311

Appendix G- Raft slab output form SAFE

Figure G.1: Bearing pressure on the soil under the foundation.

Page | 312

Figure G.2: Mx per meter run output from SAFE.

P a g e | 313

Figure G.3: My per meter run output from SAFE.

Page | 314

Figure G.4: Reinforcement per meter run in the x-direction output from SAFE.

.

P a g e | 315

Figure G.5: Reinforcement per meter run in the y-direction output from SAFE.

Page | 316

Figure G.6: Punching shear check output from SAFE.

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Figure G.7: Soil bearing pressure under the CLT foundation output from SAFE.

Page | 318

Figure G.8: CLT Raft bending moment diagram in the y-direction output from SAFE.

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Figure G.9: CLT Raft bending moment diagram in the x-direction output from SAFE.

Page | 320

Figure G.10: CLT Raft Reinforcement in the x-direction output from SAFE.

P a g e | 321

Figure G.11: CLT Raft Reinforcement in the y-direction output from SAFE.

Page | 322

Appendix H- Construction plans

P a g e | 323

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