| Mixed passenger and freight railway of unballasted tracks, characterized by thefreight-car’s heavy axle load and passenger-car’s high speed, differs from the common mixed passenger and freight railway and passenger in its dynamic response of track structure when trains pass through. In daily operation, mixed railway is more prone to be damaged, because of its heavier axle, correspondingly degrading the working performance and weakening the durability of unballasted tracks system. Besides, track irregularity, which can be treated as the stationary ergodic random process, is the major vibration source in the wheel-rail system dynamic analysis. Therefore, random vibration theory can be adopted to analyze the dynamic response of wheel-rail system. The research hereby intends, based on the vehicle-track coupled dynamic theory and random vibration theory, to analyze dynamic response of wheel-rail system of mixed passenger and freight railway with CRTS I prefabricated slab track with finite element method. Issues studied are listed as follows:(1) A wheel-rail vertical dynamics model is established guided by the vehicle-track coupled dynamic theory to calculate the dynamic response of wheel-rail system. Then, with statistic instruments, both the statistical parameters of wheel-rail force and fatigue check load of ballastless tracks,and the effect of train speed on dynamic response of slab tracks and fatigue check load, are worked out and analyzed. The results show that speed of train has little influence on mean value of wheel-rail force, but great on standard deviation and fatigue check load of tracks under freight force is larger than that under passenger force.(2) Using different trackGerman irregularity spectra and foundation stiffness as calculation parameters, the research hereby studies wheel-rail interaction forces and it’s statistical characteristics, fatigue check load, and dynamic response of slab tracks. The final calculation shows that the mean value and standard deviation of wheel-rail force is larger when German high irregularity spectra is adopted than that of the low irregularity spectra; besides, with the fatigue check load increasing, the mean value keeps unchanged, and with the foundation stiffness increasing, the wheel-rail force keeps unchanged while increasing is the standard deviation.(4) On the basis of on-site researches of CA mortar damage of CRTS I slab ballastless tracks and relevant literature, the research hereby analyzes effect of the longitudinal length of mortar damage and train speed on statistical parameters of wheel-rail force. |
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