Viscoelastic analysis of surface responses in flexible pavements under different loading conditions

Due to time-temperature dependent behavior of asphalt concrete (AC), viscoelastic analysis is necessary for understanding the mechanism of top-down cracking (TDC). In this study, a new approach for determining the viscoelastic surface responses of multi-layered asphalt pavements was developed to solve the complicated oscillating behavior and slow convergence of the integrand of Laplace-transformed step-response function at pavement surface. By employing the Lucas algorithm, the irregular oscillations were reduced to regular oscillations by separating the integrand into high- and low-frequency components. The results calculated from the proposed approach were widely verified against finite element (FE) results. According to horizontal strains calculated at pavement surface, mechanism of TDC initiation was investigated under stationary and moving loads. The results indicated that high temperature and low vehicle speed were among the predominant factors contributing to TDC initiation. In addition, TDCs were more likely to initiate at a very close distance to the tire edge.