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# Note for Highway and Traffic Engineering - HTE by Gurpreet Mains

• Highway and Traffic Engineering - HTE
• Note
• Civil Engineering
• B.Tech
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#### Note for Highway and Traffic Engineering - HTE by Gurpreet Mains

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CHAPTER 29. RIGID PAVEMENT DESIGN 29.3.1 NPTEL May 7, 2007 Warping stress The warping stress at the interior, edge and corner regions, denoted as σti , σte , σtc in kg/cm2 respectively and given by the equation 29.7-29.8.   Et Cx + µCy (29.6) σti = 2 1 − µ2   Cx Et Cy Et σte = Max , (29.7) 2 2 r a Et σtc = (29.8) 3(1 − µ) l where E is the modulus of elasticity of concrete in kg/cm2 (3×105 ),  is the thermal coefficient of concrete per o C (1×10−7) t is the temperature difference between the top and bottom of the slab, Cx and Cy are the coefficient based on Lx /l in the desired direction and Ly /l right angle to the desired direction, µ is the Poisson’s ration (0.15), a is the radius of the contact area and l is the radius of the relative stiffness. 29.3.2 Frictional stresses The frictional stress σf in kg/cm2 is given by the equation σf = W Lf 2 × 104 (29.9) where W is the unit weight of concrete in kg/cm2 (2400), f is the coefficient of sub grade friction (1.5) and L is the length of the slab in meters. 29.4 Combination of stresses The cumulative effect of the different stress give rise to the following thee critical cases • Summer, mid-day: The critical stress is for edge region given by σcritical = σe + σte − σf • Winter, mid-day: The critical combination of stress is for the edge region given by σ critical = σe + σte + σf • Mid-nights: The critical combination of stress is for the corner region given by σ critical = σc + σtc 29.5 Design of joints 29.5.1 Expansion joints The purpose of the expansion joint is to allow the expansion of the pavement due to rise in temperature with respect to construction temperature. The design consideration are: • Provided along the longitudinal direction, • design involves finding the joint spacing for a given expansion joint thickness (say 2.5 cm specified by IRC) subjected to some maximum spacing (say 140 as per IRC) Introduction to Transportation Engineering 29.3 Tom V. Mathew and K V Krishna Rao

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CHAPTER 29. RIGID PAVEMENT DESIGN NPTEL May 7, 2007 Filler h/2 Full bond No bond Figure 29:2: Expansion joint 29.5.2 Contraction joints The purpose of the contraction joint is to allow the contraction of the slab due to fall in slab temperature below the construction temperature. The design considerations are: • The movement is restricted by the sub-grade friction • Design involves the length of the slab given by: Lc = 2 × 104 Sc W.f (29.10) where, Sc is the allowable stress in tension in cement concrete and is taken as 0.8 kg/cm 2 , W is the unit weight of the concrete which can be taken as 2400 kg/cm3 and f is the coefficient of sub-grade friction which can be taken as 1.5. • Steel reinforcements can be use, however with a maximum spacing of 4.5 m as per IRC. Filler h/2 Full bond Full bond Figure 29:3: Contraction joint 29.5.3 Dowel bars The purpose of the dowel bar is to effectively transfer the load between two concrete slabs and to keep the two slabs in same height. The dowel bars are provided in the direction of the traffic (longitudinal). The design considerations are: Introduction to Transportation Engineering 29.4 Tom V. Mathew and K V Krishna Rao