Fatigue damage analysis in asphalt concrete mixtures using the dissipated energy approach

An asphalt concrete damage-energy fatigue approach based on the concept of change in dissipated energy is presented in this paper. The damage-energy based fatigue approach is simple and based on a sound theoretical background. The central concept of the energy approach is the energy fatigue curve, which is based on two key elements, namely the plateau value (PV) and the number of load cycles to true failure (N-tf). The plateau value represents the constant value of the percentage of dissipated energy that produces damage to the material under cyclic loading. Failure is defined as the number of load cycles at which this percentage of dissipated energy begins to increase rapidly, indicating instability. Flexural fatigue testing was used to test hundreds of asphalt concrete beams, mainly under controlled-strain testing conditions. It was found that PV is highly dependent on the initial loading conditions, stress, strain, and dissipated energy. As a result, it can be used conveniently in pavement design. The number of load cycles to 50% reduction in initial stiffness was found to be highly correlated with the new failure point (N-tf). Using the dissipated energy concepts in fatigue analysis makes it possible to account for damage accumulation in a straightforward manner.