Determination of Critical Concrete Pavement Fatigue Damage Locations Using Influence Lines

In an attempt to better understand and predict rigid pavement behavior, the incorporation of material and climatic factors in mechanistic-empirical design methods are fast becoming standard in the United States. With the wide variety of climatic regions found in California, the inclusion of localized factors can have a profound effect on the critical distresses and life of the pavement. Permanent built-in curling from construction temperature gradients and differential shrinkage can have a considerable effect on the location and magnitude of concrete fatigue damage. A mechanistic analysis was developed employing an influence line approach in conjunction with Miner's Hypothesis to calculate the fatigue damage at numerous locations in the concrete pavement slab for typical California rigid pavement sections. Concrete fatigue transfer functions which account for stress range or maximum stress, were used to predict the location and magnitude of critical damage. Results show that the critical cumulative damage levels and locations are highly influenced by factors such as effective built-in temperature difference, steer-drive axle spacing, load transfer level, lateral wheel wander distribution, and climatic region. For slabs with built-in curling and a combination of the aforementioned variables, top-down and bottom-up transverse, longitudinal, and corner cracking can occur. These predicted fatigue failure modes correspond well to the wide variety of observed fatigue cracking on existing California rigid pavements.