Analysis Of Vulnerability Of Multi-linked Continuous Girder Bridges Under Spatially Varying Ground Shaking

In recent decades,mega-earthquakes have occurred frequently at home and abroad,bringing significant casualties and economic losses to human society.The bridge structure occupies a pivotal position in the transportation system,and the seismic performance of the structure is getting more and more attention.With the acceleration of modernization in China,continuous girder bridges are widely used in highway construction for their strong spanning capacity,reasonable force and good continuity.High-speed continuous girder bridges are characterized by multiple long spans,and the effect of spatial variation of ground vibration is a factor that cannot be ignored in the study of seismic performance.The vulnerability analysis of such bridges under spatially varying ground shaking is of great significance in assessing the seismic level of bridge structures,predicting direct economic losses and guiding rescue and transportation work.In this paper,a multi-linked continuous girder bridge of Jingxiong Expressway is used as the engineering background,and a nonlinear dynamic finite element model is developed for the whole bridge considering both seismically isolated and nonseismically isolated cases,respectively.The paper starts from the basic theory of spatially varying earthquakes,simulates the generation of consistent and multi-point earthquake time curves,and studies the earthquake susceptibility of bridge piers and bearings under consistent excitation and multi-point excitation,analyzes the change law of bridge structure susceptibility caused by the spatially varying effect of ground shaking,and evaluates the seismic performance and seismic isolation effect of the bridge before and after seismic isolation,the main work done in this paper is as follows:(1)Based on a multi-linked continuous girder bridge project of Beijing-Xiong Expressway,a finite element model is established for the nonlinear dynamic analysis of the whole bridge under the influence of pile-soil interaction and multi-linked effect,and the multi-point ground vibration time course curve with spatial variation is simulated to analyze the structural response of the multi-linked continuous girder bridge affected by traveling wave effect,coherence effect,local site effect and other factors.(2)Based on the theory of seismic susceptibility analysis,the damage indexes and damage levels of piers and bearings of multi-linked continuous girder bridges were established,the susceptibility of bridge vulnerable components and systems under consistent and multi-point excitation were analyzed,and the damage law of bridges under spatially varying ground shaking was studied.(3)For the seismically isolated bridges with lead-core rubber bearings and friction pendulum isolated bearings,the damage indexes and damage levels of the two types of bearings were established,the seismic vulnerability analysis of the piers and isolated bearings of the seismically isolated multi-link continuous girder bridges under consistent and multi-point excitation was carried out,the seismic performance of the isolated bridge structures was studied,and the seismic isolation effects were evaluated.