Construction of a track irregularity spectrum for Chinese metros and its influence on vehicle dynamic performance

Track irregularities significantly affect vehicle dynamic performance, including safety and stability. However, previous studies on metro track irregularity spectra focused on a few lines, and a general metro track spectrum remains lacking. This study collected extensive track irregularity data from 16 metro lines in different cities in China. The irregularities were preprocessed using methods including data cleaning, recovery, and filtering. The track irregularity power spectral density (PSD) calculated using the Welch method obeyed a chi-square distribution with two degrees of freedom, indicating that a probabilistic method can be used to obtain various quantile spectra as required. The stochastic, elevated, and underground metro spectra were constructed by fitting the stochastic PSD with the fifth-order polynomial and the spectral peaks with a Lorentzian function, providing a comprehensive characterization of track irregularity. A rigid-flexible coupled dynamic model of a metro vehicle incorporating car-body flexibility was established and validated using a measured car-body acceleration. The influence of track spectra on the vehicle dynamic performance was analysed, leading to the determination of track irregularity limits. The results showed that track irregularity standard deviation positively influence the dynamic performance. Compared with the proposed limits, those specified in the current standard appear relatively conservative. The proposed track spectra provide a more comprehensive characterization of track irregularities in Chinese metros.