Dynamic Analysis Of Long-span Suspension Bridge And Vehicle System Under Un-uniform Seismic Excitation

Earthquake is a kind of serious natural disasters, which cause great damage to human being, including the safety of life and property, such as the Tangshan Earthquake, happened in1976. With the development of highway, more and more long-span suspension railroad bridges have built. Thus, the probability of a train running across a bridge has increased significantly, which would cause derailment during the earthquake. It calls for more attention to the safety of vehicle-bridge systems under seismic excitation. By studying the response of vehicle-bridge systems under seismic excitation, we can try our best to avoid the events of train derailment[1].Before, we mostly focus on the dynamic responses of bridge subjected to uniform seismic excitation. In this method, unidentical acceleration histories have to be incorporated for all the bridge nodes, while, in practice, the phase angles of seismic waves differ for different foundations, especially in the case of long-span bridges. So we have to consider the case of multi-support seismic excitation.In this thesis, we mainly consider the following three aspects in earthquake analysis: the incorporation of earthquake wave, the bridge’s natural characteristics, and the dynamic responses of vehicle-bridge system under non-uniform seismic excitation. On the basis of the study achievements at home and abroad, the case of Oujiang Bridge was studied. In the case, the dynamic responses were simulated for a high-speed train traversing the Oujiang suspension bridge with different train speeds, and the train safety was evaluated.The study includes the following aspects:(1) We compared the advantages and disadvantages of time-history approach, random vibration approach[2], the response spectrum approach. And we studied the responses of vehicle-bridge system subjected to multi-support seismic excitation.(2) We built the finite model using ANSYS program and studied the bridge’s natural dynamic properties.(3) By inputting the Tianjin wave, we found the problem of "shifting". When I correct the baseline of the wave, using the Seismosignal software, the problem was solved perfectly.(4) The responses of vehicle-bridge system subjected to non-uniform seismic excitation were studied. By comparing the results of non-uniform seismic excitations of different wave speeds and the uniform seismic excitations, we found that::1) the different wave speeds produce nearly the same effects.2) the derailment factors and offloading factors increase markedly with the increment of the train speed.