Evaluation of the Linear Damage Assumption in JPCP Bottom-up Fatigue Cracking

Current pavement design guides for Jointed Plain Concrete Pavements define one critical location at the mid-slab edge and assume that damage accumulates linearly and can be described via S-N curves. More recently, experiments have shown that damage does not accumulate linearly and a pronounced stress range effect exists. These two assumptions will lead to an accumulation of prediction error that will accrue depending on the sequence of applied loads. In this paper, a modified Paris fatigue equation developed in previous studies is used to simulate mid-slab edge damage propagation. The fatigue equation accounts for the transient and steady state stages of cracking in addition to the peak and stress range effects. An interpolation scheme was used to determine the pavement stresses at the bottom mid-slab edge. The interpolation scheme was constructed from a total of 35,000+ FEM runs in EVERFE. Intra-axle peak and valley stresses were accounted for in this analysis which is not considered in MEPDG. Two different climatic regions were considered. The results of this study suggest that damage may be unpredicted using the linear damage assumption because it does not account for the over-load effect. However, the under prediction can be corrected by re-calibrating the percent slabs cracked algorithm. Demonstration for ISCP Board only.