Fatigue Implications in Rigid Airport Pavements

Fatigue in concrete is very difficult to analytically quantify owing to the intricacies of several factors that affect concrete performance. As a result, it has been a subject of much experimental research. Fatigue effects have been incorporated into concrete design procedures including airport pavement design. This research effort studied the factors that affect concrete fatigue life in relation to an airport pavement scenario. Analysis of preliminary test results from the National Airport Pavement Test Facility (NAPTF) test site reveal that pavements experience more stress reversals and more load cycles than anticipated when a dual tandem or a tridem gear is used for loading. Stress patterns were observed at the longitudinal edge, a critical location for pavement response. Test results were supported with finite element simulations. The NAPTF was a scaled model and hence effects of gear type on stress ranges were analytically simulated for an actual airport pavement at the Denver International Airport (DIA) with B777 loads. It is concluded that the NAPTF sections are subjected to more severe loads than anticipated and might fail earlier than expected. It is recommended that effects of axle spacing be accounted for when results from these tests are related to real life airport pavements.