Prediction of stresses in concrete pavements subjected to non-linear gradients

This paper presents a technique for analyzing the residual stresses in concrete pavements subjected to non-linear (stress or strain) gradients through-our the slab thickness. The analysis is separated into two path. In the first part, an expression is presented for calculating the self equilibrated stresses within a cross-section due to internal restraints (i.e. satisfying equilibrium conditions and continuity of the strain field within the cross-section). These stresses are independent of slab dimensions and boundary conditions. In step two, the stresses due to external restraints (i.e. self-weight and sub-grade reaction) are calculated using an equivalent linear temperature gradient obtained from the first part and using existing closed form solutions by Westergaard [Westergaard, H. M., Computation of stresses in concrete roads. In Proc. of the 5th Annual Meeting Vol. 5, Part I, Highway Research Board, 1926, pp. 90-112] or Bradbury [Bradbury, R. D., Reinforced Concrete Pavements. Wire Reinforcement Institute, Washington D.C. 1947.]. The solution to this step includes slab length and boundary conditions. Total internal stresses due to non-linear gradients are obtained using the superposition principle. The proposed method has been applied to field data from another study for varying temperature profiles within a 24 h period and compared to results from conventional analysis assuming linear gradients. Significant differences were found between the two methods for night-time and early-morning conditions. A linear gradient solution sometimes underestimates tension in the bottom of a slab prior to vehicle loading by a factor of three. (C) 1997 Elsevier Science Limited.