Evolutionary power spectral density study of the earthquake-induced dynamic irregularity based on short-time Fourier transform

Abstract

The stiffness degradation of the track-bridge system under earthquake is the main reason for the deterioration of track dynamic smoothness. In order to investigate the dynamic smoothness performance of the track surface of the track-bridge system after earthquake. In this paper, a nonlinear time analysis of ballastless track-simply supported bridge system under transverse random earthquakes is carried out, and the degradation mode and degradation degree of each key component of the track-bridge system after transverse earthquakes are investigated. Based on the post-earthquake stiffness of each component, a train-track-bridge system considering earthquake-induced stiffness degradation is established. The sample library of earthquake-induced dynamic irregularity is constructed by additional deformation of rails, and the power spectral density of the earthquake-induced dynamic irregularity is studied. Based on the short-time Fourier transform irregularity inversion technique, the earthquake-induced dynamic irregularity characteristic curve based on the probability guarantee rate is proposed, and the effects of train operating speed and ground vibration intensity on the earthquake-induced dynamic irregularity characteristic curve are investigated. The research results show that: The transverse stiffness degradation of the bearings and piers of the track-bridge system is the most obvious during an earthquake, and the stiffness degradation degree of the middle piers is greater than that of the side piers. The stiffness degradation degree of the track-bridge system rises significantly with increasing PGA, while the variability of stiffness degradation of the middle and side piers drops. The most significant earthquake-induced dynamic irregularity sample is the track alignment irregularity. Low-frequency components dominate the evolutionary power spectral density corresponding to track dynamic irregularity, and the amplitude of the power spectral density reduces considerably with increasing spatial frequency. The vehicle speed has little effect on the earthquake-induced track dynamic irregularity. The irregularity amplitude grows significantly with increasing damage degree. The results indicated that the stiffness degradation damage degree of the track-bridge system under earthquake can be quantified by constructive earthquake-induced track dynamic irregularity.