A spectral analysis of the dynamic frequency characteristics of asphalt pavement under live vehicle loading

By employing the equivalent thickness concept and the 45° time diffusion approach, the Mechanistic-Empirical Pavement Design Guide (MEPDG) determines the dynamic frequency of pavement subjected to vehicle loading; however, this method has been proven inaccurate. To investigate the in situ dynamic response of pavement, strain gauges were embedded in newly constructed pavement, and dynamic response data for various loadings and speeds were collected. The dynamic frequency of asphalt pavement under live vehicle loading was investigated from a spectral perspective using the fast Fourier transform (FFT) method. Composite and semi-rigid structures were compared using a representative frequency, which is defined by the weight centre in the FFT plot. The results show that the representative frequency increases with increasing speed and decreases with increasing loading magnitude and temperature. The representative frequencies of the two different structures present a significant difference. The representative frequencies measured by different sensors appear to be equivalent for speeds exceeding 40 km/h on the composite structure section. The approach utilised in the MEPDG underestimates the asphalt pavement frequency; thus, to provide reliable dynamic parameters of asphalt mixtures under live loading for pavement design, a reference approach with a master curve envelope was introduced to determine the representative frequency by considering the coupling effects of speed, loading and temperature. The rationality of the master curve was demonstrated accordingly.