Study On Probability Distribution And Dynamic Reliability Of Train-Bridge System Response Under Random Seismic Loading

The damage of bridges under earthquake seriously affected people’s daily lives and the aftermath. At the same time, there is a great chance to threaten the train running safety on the bridge. Therefore, seismic response analysis is very necessary.Ground motions have three basic vibration characteristics, i.e., amplitude, spectra and duration. They play decisive roles in seismic response analysis and all have significant randomness. Therefore, it’s very reasonable that theory of random vibration applied to seismic analysis in bridge. In the dissertation, based on theory of random vibration and with continuous beam bridge with 5 spans for study, the train-track-bridge coupled vibration model is established. Independently developed program of Train-Track-Bridge-Seismic Analytical System (TTBSAS) is used to study the probability statistical characteristics and the reliability of response of random system under random seismic load. The main works and achievements are listed as follows:(1) Considering the spatial variation characteristics, i.e., traveling wave effect, local site effect, no coherent effect, damping effect of multi-point ground motions, Clough-Penzien spectrum is taken as auto-power spectrum and Qutiejun-Wangjunjie model is taken as coherence function. Artificial seismic waves are generated with multiplicative congruential method that taking intensity factor and filter parameters in auto-power spectrum as random variables.(2) With Monte-Carlo simulation method, analyzing the probabilistic statistical characteristics of system response under synthetic seismic waves. The results show that vehicle response that acceleration, derailment coefficient, wheel unloading rate and extreme value I distribution are in good agreement, lateral displacement of middle span of the bridge and extreme value I distribution are in good agreement, the vertical displacement and acceleration of middle span of the bridge and lognormal distribution are in good agreement. The speed of train and traveling wave effect are no impact on the probabilistic statistical characteristics of response.(3) According to the curve of probabilistic statistical characteristics of response, obtaining the dynamic reliability of each response of middle span of the bridge corresponding to the threshold value and the dynamic reliability of response of the train corresponding to the threshold value based on criterion of running safety and comfort of train. The results show that response threshold increases with reliability and the random seismic will not affect the train running safety but the comfort according to the traditional indexes of evaluation of train running safety and comfort.