Seismic Response Analysis Of Long-span Bridge Considering Earthquake And Vertical Trainloads

ABSTRACT:The bridge is an important component of lifeline engineering, it's power to resist disaster is especially important. The aseismatic study of bridge structures is recognized widely after much damage in previous earthquake. Many scholars have engaged in this study and made great progresses. However, the earthquake damage of the modern bridge is very serious during the recent earthquake; it indicates that the aseismatic design theory and method of bridge used in the present are also insufficiency. Bridge overall seismic performance can not be learned comprehensively accounting for multiple excitations, terrain effects or SSI effect separately during seismic Calculation of the bridge, as a result, bridge overall dynamic analysis method accounting for above factors simultaneity is essential. Meanwhile, the dynamic analysis of coupled train-bridge system subjected to earthquakes is separated into aseismatic analysis of bridge and train-bridge coupled vibration, which is not consistent with the actual situation. It's necessary to construct the overall foundation, bridge and train model. The main studies in this dissertation are listed as follows:1. The multi-sources scattering viscous-spring artificial boundaries is proposed based on single-source scattering viscous-spring artificial boundary, combined with multi-points scattering problem such as bridge, railway and so on. It can be used in endogenous multi-loads and multi-seismic dynamic loads cases, the multi-seismic dynamic loads input can be realized by applying equivalent loads on the artificial boundaries. The numerical calculate is carried and the results indicate the proposed method in the paper can improve the accuracy of viscous-spring artificial boundary compared with the situation of single scattering source. The introduction of the boundary conditions provides a theoretical basis for the bridge seismic wave seismic multi-input.2. Based on the viscous-spring superposition artificial boundaries theory, a finite element two-dimension model accounting for incident angle, soil-structure dynamic interaction and topographic effect is built by using the software and a seismic responses analysis of a five-span continuous bridge was carried out by method. The numerical results demonstrate that local topographic effect, physical properties of soil, SSI and seismic incidence angle play a certain role in seismic analysis of the bridge. 3. The equivalent loads of inclined sv/p wave on the artificial boundaries are proposed by combining the viscous-spring artificial boundary theory, stress-strain relation of materials and wave motion theory in three-dimensional model. A finite element three-dimension model which is involved with foundation, accounting for incident angle, incident direction, soil-structure dynamic interaction and topographic effect is built by using the software and a seismic responses analysis of a four-span rigid frame bridge was carried out by method. The parameters of bridge are varied in order to calculate the influence of different parameters. The numerical results demonstrate the influence of different parameters to bridge is relevant to incident angle, incident direction and waveform, the interaction restriction relations exist among those factors.4. A model involved into foundation, bridge and train is built based on the artificial boundary, the dynamic responses of the train-bridge system are calculated under various conditions that the train running at different speeds with SV seismic waves input. By comparing the results to those without earthquakes, various factors such as SSI, different wave incident degree and the train speeds influencing on the dynamic response of the train-bridge system are discussed.