Journal of the IndIan roads Congress

Journal of the Indian Roads Congress Volume : 78 - 1 ● april - June, 2017 ● ISSN 0258 - 0500 Indian Roads Congress Founded : On 10th December, 1934

Publisher & Editor: S.K. Nirmal, Secretary General, IRC E-mail: [email protected],

www.irc.nic.in

Headquarter: IRC Bhawan, Kama Koti Marg, Sector-6, R.K. Puram, New Delhi-110 022. Satellite Office: Ground Floor, IDA Building, Jamnagar House,Shahjahan Road, New Delhi-110 011. Phone No.: +91-11-26171548 (Admn.), 23387140 & 23384543 (Membership), 23387759 (Sale), 266185273 (Tech. Papers, Indian Highways and Tech. Committees) No part of this publication may be reproduced by any means without prior written permission from the Secretary General, IRC. The responsibility of the contents and the opinions expressed in Journal of the Indian Roads Congress is exclusively of the author(s) concerned. IRC and the Editor disclaim responsibility and liability for any statements or opinion, originality of contents and of any copyright violations by the authors. The opinion expressed in the papers and contents published in the Journal of the Indian Roads Congress do not necessarily represent the views of the Editor or IRC.

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CALL FOR TECHNICAL PAPERS 1.

The Indian Roads Congress (IRC) invites Technical Papers for publication in its periodicals i.e. Indian Highways (monthly), IRC Journal (quarterly) and HR Journal (half yearly). 2. The contents of papers should cover the additional knowledge, information and ideas so that highway fraternity gets benefitted from them. The papers should be properly structured and should avoid dwellings at lengths on facts broadly known to highway engineers. The papers may deal with important case studies, new design concepts/ principles, new construction techniques, modern quality control, modern maintenance techniques applied in highway projects, besides traffic engineering, transport planning etc including a paragraph on application of Paper to Highway Profession and updation of IRC Codes. 3. Authors and Co-authors should be members of IRC and their Roll Numbers should be mentioned in the forwarding letter. Even non-members, who are Experts in any relevant field or who have specialized knowledge on any subject related to highway engineering are also welcome to contribute Technical Papers. 4. The Authors are requested to send a hard copy of the complete paper consisting manuscript, drawing, tables, figures, photos, etc. and soft copy through E-mail: [email protected] for printing. 5. The papers so received from Authors are sent to a panel of experts and are considered for publication after obtaining their views about acceptability of the paper. 6. IRC reserves the right to publish any paper in the form of an abstract. When a paper is published in an abstract form, the manuscript of the paper as sent by the author will be added to the IRC library and made available for inspection by interested members. For more details and rules for contribution of Technical Paper please visit IRC Website: www.irc.nic.in

EMPANELMENT OF REFEREES Call of Expression of Interest from the experienced Road & Bridge Technocrats for Formulating a Panel of Experts/Referees to Review the Technical Paper, voluntarily: In order to align with the globally best practices and promote the excellence in road construction, the Indian Roads Congress (IRC) is in the process of formulating a Panel of Experts/Referees who can review the Technical Papers received in IRC from Authors. Road Technocrats who are already members of the IRC and have experience and expertise in the field of Transport Planning, Traffic Engineering, Flexible & Rigid Pavements, Rural Roads Development, Mechanization & Instrumentation, Road Maintenance, Safety & Design, Bridge Design Features, Concrete Structure, Maintenance &Rehabilitation of Bridges etc. are invited to show their interest for evaluation of Technical Papers. The interested technocrats are requested to send their brief resume including their experience in related field with their IRC Membership Number to IRC on E-mail: [email protected]

Paper No. 663 An Examination of Structural Safety of Concrete Pavements with Wider Panels

Swarna Suryateja1

Prof. M. Amaranatha Reddy2

Prof. B. B. Pandey3

ABSTRACT Construction of concrete pavements has gained momentum in India for reasons of durability, maintenance free service and lower life cycle cost. Stress computation in the Guidelines for the Design of Plain Jointed Rigid Pavements for Highways (IRC:58-2011 and IRC:58-2015) is given for 3.5 m wide pavement with and without tied shoulder while slab widths of 4 m, 4.5 m and 5.0 m are being adopted with a single longitudinal joint in a 9 m or 8.5 m wide pavement. It is, therefore, necessary to examine the stresses for bottom-up and top-down cracking for the slab sizes of greater widths adopted in practice. There is a possibility of Longitudinal Top - Down Cracking (LTDC) during the night hours due to tandem and tridem axles. The paper presents analyses of pavements of different widths using Finite Element Approach and it is found that stresses may not cause bottom up cracking. However, there is a possibility of longitudinal cracking if load transfer across the longitudinal joints is not ensured. Existing recommendation for lane addition in IRC:58-2015 needs to be amended to ensure load transfer at joints. 1.

INTRODUCTION

Construction of Jointed Plain Concrete Pavements (JPCP) has become a priority of the Ministry of Road Transport and Highways for major highways in spite of higher initial cost due to nagging maintenance problems of bituminous pavements and traffic disruption for maintenance. Four lane divided carriageway with paved shoulder has a pavement width of 9.0 m in each direction and transverse joints are provided at every 4.5 m while the longitudinal joints with tie bars are usually 3.5 m apart coinciding with the lane markings as outlined in IRC:58-2015. Tied concrete shoulder is 1.5 m wide while the total width of the inside concrete slab is 4.0 m including 0.5 m of kerb side margin. In a number of 9 m wide concrete pavements, the contractors have adopted a different pattern of longitudinal joints to reduce the cost of one longitudinal joint cutting. In some 1 2 3

projects, a single longitudinal joint is provided in the mid slab with a width of the concrete slab being 4.5 m on either side of the joint while in some others, a single longitudinal joint is provided 4 m from the median, the outer slab width being 5 m with 1.5 m forming the part of the shoulder. While the longitudinal joints as per IRC:58-2015 lies on the lane marking, the widths of pavement slab are found to be 4.00 m, 4.50 m and 5.00 m in many projects as shown in Fig. 1. Wheel paths falling on the longitudinal joints may damage the pavements early if lane marking do not lie on the joint. In Fig. 1(a), two longitudinal joints, one is 1.5 m away from the left edge and other is in between the two lanes. In Fig. 1(b), the width of slab on the left side is 4.5 m while lane marking is done 1.5 m from the left edge and again at 3.5 m from shoulder marking. It can be seen that distance between the outer lane marking and the longitudinal joint is

Masters Student, E-mail: [email protected]; Tel: +91-7416801990 Associate Professor, E-mail: [email protected]; Tel: +91-9434737788 Advisor, Sponsored Research and Industrial Consultancy and former Professor, E-mail: [email protected]; Tel: +91-9434054439

Department of Civil Engineering, Indian Institute of Technology Kharagpur, West Bengal,

Journal of the indian Roads Congress, April - June, 2017

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Paper No. 663 3.0 m and considering that the wheel path may be about 0.5 to 0.75 m away from the outer lane marking, most of the inner wheel path of heavy commercial may fall on the longitudinal joint. Since the outer lane is assigned to Heavy Commercial Vehicles (HCV), percent repetitions of HCV in the outer lane for thickness design can be much larger than 25% assigned in IRC:58-2015. In Fig. 1(c), the width of slab on the shoulder side is 5.0 m while lane marking is done 1.5 m from the shoulder edge and again at 3.5 m from shoulder marking which exactly come over the longitudinal joint. If the single longitudinal joint is 4.0 m from the median, the wheel paths are away from the longitudinal joints. Wider slabs, however,

Two longitudinal joints, one is 1.5 m away from the left edge and other is in between the two lanes

must be checked for longitudinal cracks caused by the combined effect of temperature gradient and single, tandem and tridem axle loads. A survey of lateral placement of wheel path of HCV (Fig. 2) was made on the four lane divided concrete road,NH-60, between Balasore and Kharagpur and the results, are shown in Fig. 3. It can be seen that with a single central longitudinal joint 4.0 m from the median, the wheel paths do not fall on the longitudinal joints while for the longitudinal joints at mid slab, repetitions of wheel path are large. This paper presents an analysis of stresses in wider slabs considering the apprehension of the professionals that stresses in pavements may be too high leading premature failure of pavements.

Single longitudinal joint in the middle

Single longitudinal joint at 4 m from the median Fig. 1 Lane Marking and Location of Longitudinal Joints in Different Types of Jointed Concrete Pavements 22


Paper No. 663

Fig. 2 Markings on the Existing Concrete Pavement for Wheel Path Survey

Fig. 3 No. of Wheels Coming on to the Slab Throughout the Width of the Slab

Curling in day and night hours: While stresses by axle loads for wider slabs are not much different from 3.5 m wide slabs for edge loading during the day hours during the curled condition shown in Fig. 4, the night time curling and stresses due to tandem and tridem axle loads need to be determined during the curled condition. 2.

THREE DIMENSIONAL FINITE ELEMENT (3D FE) MODELLING

The 3D FE model of the slab was done in ANSYS 15.0, which is used to model the combination of load and temperature effects on the pavement slabs of dimensions mentioned above dimensions.

The FE modelling of the pavement is shown in Fig. 5.

Fig. 4 Tridem Axle Load Over a Curled Concrete Pavement during the Night Hours


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Paper No. 663 IRC:58-2015. Rectangular tire imprints of size 240 mm x 160 mm corresponding to a single wheel load with varying pressure were considered for the stress analysis of the pavement slab. Subsequently, the contact pressure was made to vary from 0.65 to 1.30 MPa corresponding to axle loads varying from 10º kN to 20º kN for a given geometry. Computed values of tensile stresses are presented in the following. Fig. 5 Finite Element Model of Concrete Pavement

Unlike IRC:58-2015 method, DLC is considered as a structural layer because of its high shear strength. The pavement slab and the DLC were modelled as 8 noded solid brick elements (SOLID185) with a plastic sheet at the interface. A contact element was used to model the plastic sheet. The granular subbase and subgrade were modeled as a set of linear discrete elastic springs (COMBIN14) considered as Winkler foundation designated by the effective modulus of subgrade reaction k of value 62 MPa/m. Finite element analysis was carried out to find out the effect of increased slab width. As per IRC:58-2015, a three-layer Pavement system is considered with a subgrade of 10% CBR, granular Sub base and DLC thicknesses 150 mm and 150 mm respectively fora 250 mm thick PQC. Three different panel sizes namely 3.5 m × 4.5 m, 4.5 m × 4.5 m and 5 m × 4.5 m are considered for the analysis. Properties considered for analysis are shown in Table 1. Axle loads were applied to analyze the pavement system for bottom- up cracking and top-down cracking as stated in IRC:58. For the location, Kharagpur, West Bengal, India, the maximum daytime temperature differential of 15.8ºC and for night time is 15.8/2 + 5 = 12.9ºC as per

Table 1 Properties Considered for Analysis Properties Modulus of Elasticity (MPa) Poisson’s Ratio Coefficient of thermal expansion (/ºC) Reference Temperature (ºC) 3

Density (kg/m )

DLC

30000

13600

0.15

0.25

1x10-5

1x10-5

35

35

2400

2000

Three different critical conditions of Transverse Bottom Up Cracking (TBUC), Transverse Top Down Cracking (TTDC) and Longitudinal Top Down Cracking (LTDC) were considered for analysis. Three different loading cases considered for analysis are i) Single axle dual wheel loading at theedge of the slab shown in Figs 6(a), 7(a) & 8(a). ii) Front single axle single wheel and rear single axle dual wheel on both ends of the slab represented by case 2 as shown in Figs 6(b), 7(b) & 8(b). iii) Tridem axle load near the dowelled joint of slab represented by Case 3 as shown in Figs 6(c), 7(c) & 8(c). Three slab dimensions are considered with respect to “tied shoulder” those are 3.5 m × 4.5 m, 4.5 m × 4.5 m and 5 m × 4.5 m panel sizes.

Fig. 6 Loading Positions Considered for Analysis of 3.5 m × 4.5 m Slab 24

PQC


Paper No. 663

Fig. 7 Loading Positions Considered for Analysis of 4.5 m × 4.5 m Slab

Fig. 8 Loading Positions Considered for Analysis of 5.0 m × 4.5 m Slab

Results of analysis of a concrete pavement with 250 mm PQC + 150 mm DLC + 150 mm GSB and

subgrade CBR = 10 % are given in Table 2. The effective k-value above GSB is 62 MPa/m.

Table 2 Flexural Stresses (MPa) for Different Loadings with Change in Slab Dimension

Condition Day Time (21°C) (TBUC) Case 1 Night Time (15°C) (TTDC) Case 2 Night Time (15°C) (LTDC) Case 2 Night Time (15°C) (LTDC) Case 3

Loadings Temperature + Load (100kN) Temperature + Load (120kN) Temperature + Load (160kN) Temperature + Load (200kN) Temperature + Load (100kN) Temperature + Load (120kN) Temperature + Load (160kN) Temperature + Load (200kN) Temperature + Load (100kN) Temperature + Load (120kN) Temperature + Load (160kN) Temperature + Load (200kN) Temperature + Load (100kN) Temperature + Load (120kN) Temperature + Load (160kN) Temperature + Load (200kN)

3.5 m 2.42 2.63 3.14 3.52 1.77 2.17 2.76 3.26 1.55 2.01 2.67 3.17 1.69 2.23 2.96 3.51

4.5 m 2.42 2.63 3.14 3.52 1.87 2.25 2.82 3.27 2.01 2.44 2.86 3.24 2.17 2.69 3.17 3.59

5.0 m 2.35 2.57 3.08 3.46 1.92 2.30 2.86 3.26 2.28 2.62 3.00 3.34 2.45 2.86 3.32 3.70


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Paper No. 663

Fig. 9 Variation of Stress Due to Change in Slab Dimension

3. DISCUSSION OF RESULTS Results for axle load of 100 kN, 120 kN, 160 kN and 200 kN with a temperature differential of 21ºC indicates that when width of the panel is increased from 3.5 m to 5 m , for an axle load of 200 kN, there is no increase in stresses for bottom up cracking while there is a marginal increase in stresses on the top surface during the night. For lower axle load (< 200 kN), the increase in flexural stresses in top surface during the night hours is much higher. Wider panels may, however, undergo longitudinal cracking due to non-uniformity of foundation across the formation width though theoretically, the pavement is safe. When a lane is added for the widening of a pavement from two lane to three lane in each direction, wheel path may fall on the joint itself and only dowel bar can transfer the load across the longitudinal joint for a long period of time. CONCLUSIONS From the analyses of pavements of different widths using Finite Element Approach, following conclusions are drawn.  Stress computation in IRC:58-2015 is given only for 3.5 m wide pavement while slab widths of 4 m, 4.5 m and 5 m are being adopted with a single longitudinal joint in a 9 meter wide pavement.

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





There is little change in stresses with the increase in slab width. But wheel path survey shows that the wheel paths lie on the central longitudinal joint of the 9 m wide pavement. If the longitudinal joint in a 9 m slab is placed at 5 m from the edge then the pavement could perform better compared to all other slab sizes. As there is an increase in width of the pavement slabs, there is an increase of stresses in the longitudinal direction which may lead to longitudinal cracking for heavy loads.

REFERENCES 1. IRC:58-2011., Guidelines for the Design of Plain Jointed Rigid Pavements for Highways, The Indian Roads Congress, New Delhi, India. 2. IRC:58-2015, Guidelines for the Design of Plain Jointed Rigid Pavements for Highways, The Indian Roads Congress, New Delhi, India. 3. Lawrence KL., ANSYS workbench tutorial release 14. SDC publications; 2012. 4. Ministry of Road Transport and Highways, Specifications for Road and Bridge Works, MoRTH, 5th Revision, Indian Roads Congress, New Delhi, India, 2013.
