Seismic Response Analysis Of Structural Parameters For Continuous Beam Bridge Under Multi-Support Excitation

In the recent years, with the development of traffic, a lot of long span continuous beam bridges have been constructed. In our country, earthquake happens so frequently that it is very important to study the seismic response of the long span continuous beam bridges under multi-support excitation. It is very useful to the aseismatic design and identification and reinforcement. Based on above, the thesis draws lessons from a built bridge and the newest research achievement studying and analysising dynamic parameter design of long span continuous beam bridge, obtains some valuable conclusions which will give some reference for practical aseismatic design of continuous beam bridges.Seismic ground motions can vary significantly over distances which are of the same order of magnitude as the dimensions of some extended structures, such as bridges. Three phenomena are responsible for these variations: the difference in the arrival times of seismic waves at different stations; the loss of coherency of the motions due to reflections and refractions of the waves in the heterogeneous medium of the ground, as well as due to the difference in the manner of superposition of waves arriving from an extended source at various stations and the difference in the local soil condition at each station. They influence the amplitude and frequency content of the bedrock motion, but the existing bridge criterion use response spectra theory about aseismic analysis considering uniform excitation, so multi-support excitation analysis for bridge structure is very important.This thesis introduces characteristics and affect factors and attenuation relation of seismic ground motions, as well as confirmation of designing parameters and input model firstly; Secondly the basic theory of time-history analysis are presented minutely. the equations of motion of long-span bridges under multi-support excitation are deduced and numerical solution method is introduced; In the end, a numerical simulation model of continuous beam bridge is built by the bridge special software-MIDAS/Civil. And the seismic response rules of a continuous beam bridge, which is changed a long with main span length, longitudinal stiffness of brake pier, number of bridge spans, ratio of side to main span height of piers and constrain types, are studied with the time-history analysis method considering the interaction of pile-soil-structure system. In all above calculating model only longitudinal excitations are carried out. The following conclusions are given based on a large amount of numerical analyses:1. Increasing the span length and adding the span number is bad for resisting earthquake;2. Decreasing the stiffness of brake pier or increasing height of piers is beneficial for resisting the earthquake;3. Changing the ratio of side to main span can bring advantages and disadvantages for aseismic performance of continuous beam bridges;4. Changing the constrain types of the continuous beam bridge in this thesis has little effect on aseismic performance;5. Comprehensive analysis of each structural parameter shows that the length of main span is the most hypersensitive factor for aseismic performance.