OPTIMIZATION OF CONCRETE SLAB GEOMETRY FOR ENHANCED RIGID PAVEMENT PERFORMANCE AND SERVICE LIFE

The objective of this project was to identify the effect of slab geometry on the stresses induced in dowel jointed concrete pavement slabs due to the combined effect of thermal gradient and moving traffic loads. Nonlinear 3D Finite Element was used to simulate the rigid pavement structure. The model was verified by comparing its response to a three-axle dump truck with the actual response measured on an Ohio test road using strain gauges. The influence of different parameters such as slab length, slab thickness, axle load speed, axle load magnitude, axle configuration, and concrete modulus of elasticity was investigated. Different magnitudes of nonlinear positive and negative thermal gradients that vary up to +/- 26 deg F were applied through the concrete slab thickness and the model response was obtained for both tandem and tridem axle loading. The results indicate that the combination of axle loading and positive temperature gradient applied to an initially flat slab produces high stresses that may lead to bottom-up cracks. Under negative gradient conditions, axle loading may lead to top-down cracks. The stresses induced in a 20 ft slab are generally larger than the stresses induced in a 15 ft slab under the same conditions of thermal gradient and moving axle loads. The major recommendation of this project is that thermal stresses due to temperature variations should be accounted for in concrete pavement design procedures. Edge loading should be used as the most critical loading position in designing rigid pavements. The levels of stresses observed under different loading conditions are small compared to the failure stress of concrete. Skewed joints did not show any significant improvement in performance over straight joints.