# Rigid-Pavement Design

1. You have been asked to design the pavement for an access highway to a major truck terminal. The design daily truck traffic consists of the following: 80 single axles at 22,500 lb each, 570 tandem axles at 25,000 lb each, 50 tandem axles at 39,000 lb each, and 80 triple axles at 48,000 lb each. The highway is to be designed with rigid pavement having a modulus of rupture of 600 lb/in2 and a modulus of elasticity of 5 million lb/in2. The reliability is to be 95%, the overall standard deviation is 0.4, the drainage coefficient is 0.9, ΔPSI is 1.7 (with a TSI of 2.5), and the load transfer coefficient is 3.2. The modulus of subgrade reaction is 200 lb/in3. If a 20-year design life is to be used, determine the required slab thickness.

2. A rigid pavement is being designed with the same parameters as used in Problem 4.5. The modulus of subgrade reaction is 300 lb/in3 and the slab thickness is determined to be 8.5 inches. The load transfer coefficient is 3.0, the drainage coefficient is 1.0, and the modulus of elasticity is 4 million lb/in2. What is the design modulus of rupture?

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3. A rigid pavement is designed with a 10-inch slab, an Ec of 6 million lb/in2, a concrete modulus of rupture of 432 lb/in2, a load transfer coefficient of 3.0, an initial PSI of 4.7, and a TSI of 2.5. The overall standard deviation is 0.35, the modulus of subgrade reaction is 190 lb/in3, and a reliability of 90% is used along with a drainage coefficient of 0.8. The pavement is designed assuming that traffic is composed entirely of trucks (100 per day). Each truck has one 20-kip single axle and one 42-kip tandem axle (the effect of all other vehicles is ignored). A section of this road is to be replaced (due to different subgrade characteristics) with a flexible pavement having a SN of 4 and is expected to last the same number of years as the rigid pavement. What is the assumed soil resilient modulus?