Time–Frequency Domain Analysis of Asphalt Longitudinal Strain

Abstract

The application of time–frequency domain analysis methods, such as continuous wavelet transform (CWT) and short-time Fourier transform (STFT), is evaluated in the extraction of the dominant frequency from asphalt longitudinal strain signals. The pavement response data collected at the fully instrumented Integrated Road Research Facility in Edmonton, Alberta, Canada, was used in this study. Promising results were achieved when CWT and STFT were used to determine the dominant frequency of the measured longitudinal strain at the bottom of the asphalt layer at different vehicular speeds. The dominant frequencies obtained from these methods were compared with those from conventional time-to-frequency conversion methods. Results showed that a frequency calculation that used the inverse of tensile pulse duration led to noticeably larger frequencies compared with those associated with the CWT and STFT methods. The accuracy of the determined frequencies and the corresponding moduli of hot-mix asphalt were evaluated by predicting strains with the KENPAVE program. This analysis showed the advantage of using time–frequency domain methods because they led to more reasonable agreements between the measured and predicted responses. Finally, the impact of frequency calculation methods on the potential fatigue cracking life was assessed by taking the estimated moduli and strains of hot-mix asphalt into account. It was found that the fatigue cracking life can be overestimated by almost 45% when frequency is considered as a reciprocal of pulse duration compared with when prediction is based on time–frequency domain methods.