The development of material property relations for the two fatigue damage properties, k sub 1 and k sub 2, which can be used to predict the fatigue life of asphaltic concrete pavements, is described. The fatigue damage properties developed are based on the theory of fracture mechanics along with regression analysis on published beam fatigue data and, thus, can take into account crack initiation, propagation, and material properties that are not accounted for with the conventional strain-based fatigue equation. The approach provides more insight into how these fatigue damage properties reflect the fatigue behavior of asphaltic concrete pavement while producing acceptable estimates of field fatigue life. Derivations have shown that the fatigue damage property k sub 1 is dependent on the asphalt mixture and pavement properties, such as the parameters of the paris crack growth law, elastic stiffness, and thickness of the asphaltic concrete layer and that the fatigue damage property k sub 2 varies with theinitial asphalt cement properties, such as asphalt content, viscosity, penetration, and temperature. Two significant functions of the fatigue damage properties developed are (a) the prediction of fatiguelife allows for the application of loading with single or dual tires on single, tandem, or triple axles, and (b) they provide for the calculation of load equivalence factors for fatigue life as affected by multiple-axle loads. A shift factor that can be used to adjust the laboratory (or calculated) fatigue damage properties to that measured in the field is also described. This factor takes into account healing and residual stresses between applications of traffic loads that are responsible for the difference in fatigue life between laboratory test results and those measured in the field. This paper appears in transportation research record no. 1286, Design and evaluationof rigid and flexible pavements 1990.
Abstract