A six-lane concrete roadway is being designed for a metropolitan area. This roadway will be constructed on a subgrade with an effective modulus of subgrade reaction k of 170 lb/in3. The ESALs used for the design period is 2.5 × 106. Using the AASHTO design method, determine a suitable thickness of the concrete pavement (to the nearest 1/2 inch), provided that the working stress of the concrete to be used is 650 lb/in2 and the modulus of elasticity is 5 × 106 lb/in2. Assume the initial serviceability is 4.75 and the terminal serviceability is 2.5. Assume the overall standard deviation, So, is 0.35, the load transfer coefficient J as 3.2, the drainage coefficient, Cd, is 1.15, and R = 95%.
What will be an ideal response?
First, determine the design serviceability loss
design serviceability loss = 4.75 – 2.5 = 2.25
From the nomographs provided in Figures 20.13 and 20.14 and the factors above,
the required thickness of the concrete slab is 7.8 inches, which for design may be
rounded up to 8 inches.
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