Study On Seismic Vulnerability Of Continuous Beam Bridge In High-speed Railway

In recent years,the frequency of large earthquakes at home and abroad has been increasing,which has brought considerable loss and damage to the civilization and economy of human society.As an important part of the traffic lines,bridge structures have shown that they are the most vulnerable engineering structures in many strong earthquake disasters.In twenty-first Century,high speed railway has achieved remarkable achievements in China.Continuous beam bridge has been widely applied on high speed railway line because of its strong span bridge,clear force,mature construction technology,good continuity and economic superiority.The study of earthquake vulnerability can predict and prevent earthquake damage to a certain extent,and it is of great significance to reduce the direct and indirect losses after the earthquake.Combined with the engineering practice,the main research work includes the following aspects.The main contents are as follows:(1)the purpose and significance of bridge seismic vulnerability are introduced by consulting a lot of documents.Based on the research of scholars at home and abroad,the analysis flow of seismic vulnerability analysis is described in detail from the aspects of earthquake motion selection,earthquake motion input and the quantitative standard of damage index.(2)Based on a typical continuous beam bridge in a practical project,a MIDAS/Civil spatial finite element analysis model is established.The Rayligh-Ritz method is used to analyze the natural vibration characteristics of the bridge,which lays a foundation for the nonlinear time-history analysis of the structure.(3)The control cross section of the structure is determined by inputting the ground motion records according to the conditions of the site where the structure is located.The moment curvature analysis of the control section is carried out by using XTRACT software,and the displacement ductility ratio is selected as the quantitative index,and the damage of the structure is divided into five failure grades.(4)Using SIMQKE software,20 artificial seismic waves with the same site condition are fitted,and the nonlinear time-history analysis of the structure is carried out based on the IDA method,and the seismic response and seismic intensity parameters are analyzed by regression analysis.The peak acceleration value corresponding to slight damage,moderate damage and severe damage is about 0.17 g,0.225 g,0.67 g,which is basically consistent with the idea of‘small earthquake is not bad,medium earthquake is repairable,and large earthquake cannot be collapsed' in current seismic design.