Non-Stationary Random Vibration Analysis For Vehicle-Bridge Coupled Systems

With the development of modern high speed railroads, the number of railway bridges is growing rapidly, such as the Beijing-Shanghai High-speed Railway which is planned to be built. In order to preserve the track regularity and stability, high level bridges which may extend several kilometers or even longer often need to be built. As the percentage of bridges in the whole line is becoming higher and higher, it is possible that the train is moving on the bridge when earthquake happens. In order to ensure the reliability of high speed trains, the dynamic analysis of train-bridge coupling system under random earthquake has become a significant issue to be studied. The main factor that causes the vertical random vibrations of train-bridge coupling systems is track random irregularity, considering that the earthquake loads are also random, so it is reasonable to use the theory of probability and statistics to study this problem. In this paper, the pseudo-excitation method (PEM) and the precise integration method (PIM) are employed to study the vibrations of train-bridge coupling time-varying system under non-stationary random earthquakes. The main research work concludes: The PEM is applied to time-varying system subjected to multidimensional non-stationary random excitations, and a precise and efficient algorithm is suggested to analyze the non-stationary random vibrations of three-dimensional train-bridge coupling system under random earthquakes. According to multidimensional PEM of time-varying system, the analysis of non-stationary random vibrations is transformed to deterministic time-history analysis, and the PIM is applied to solve the problem, which can factually simulate the continuous movement of the train. Finally the non-stationary random vibration for three-dimensional train-bridge coupling system subjected to earthquakes is analyzed. A numerical simulation for some type of high speed train is carried out to analyze the dynamic behavior of train-bridge coupling system with different parameters and environmental load conditions, and some useful conclusions are suggested, for instance, the earthquake load is the chief control load that induce the random vibration of train-bridge coupling system, earthquake waves of different ground conditions have certain effect on the system response, the system random response excited by earthquake is not sensitive to the train speed, the random response induced by track irregularity excitation can be significantly affected by the train speed, the high frequency component of the vibration can be weakened quickly by adjusting the modulation factor in the non-uniform modulation function, so for the response significantly affected by high frequency in the system, it is of great importance to consider the effect of non-uniform modulation. The result of this paper can be useful for the design, construction and maintenance of railroad bridges. It may also contribute to the related researches in the realm of non-stationary random vibration for train-bridge coupling system.