Seismic Performance Analysis Of Multi-span Continuous Beam-arch Composite System Bridges

Continuous beam-arch bridges are becoming more and more widely popular,so it is very necessary to study their seismic performance.At present,there are few studies on the dynamic performance of long-span continuous beam-arch composite system bridges.In this paper,a continuous beam-arch composite bridge is used as an engineering example to conduct seismic analysis.The study of the dynamic performance of the span continuous beam-arch combination system also provides a basis for the design of the bridge structure of this system.This article has conducted the following aspects of research:Firstly,the nonlinear dynamic time history analysis is carried out on the continuous beam-arch combination system to determine the unfavorable stress position of the bridge structure,the structural control section is selected,and the internal force response and displacement response are calculated.And considering the influence of the adjacent connecting structure on the main bridge structure,its seismic response is calculated.The analysis results show that the seismic response of the continuous beam-arch composite system bridge is similar to that of the beam bridge.The fixed pier of the substructure is subjected to large forces under the earthquake action along the bridge.Under the action of the transverse bridge to the earthquake,all piers are evenly stressed.This is because the fixed pier bears the main seismic effect under the earthquake action along the bridge,while the seismic action along the cross bridge direction is shared by all the piers.After adding adjacent structures,the internal forces of the transition piers have increased or decreased to varying degrees,while the seismic responses of the other piers have not changed much.Since the maximum single-span span of the bridge reaches 160 m,the traveling wave effect will have a greater impact on the seismic response of the bridge structure.Therefore,the internal force and seismic response of the bridge structure under the seven load conditions of 600m/s,800m/s,1000m/s,1200m/s,1400m/s and uniform excitation were calculated by nonlinear dynamic time history analysis.At the same time,the friction pendulum seismic isolation support is used to establish the seismic isolation system of the bridge structure,and the nonlinear dynamic time history analysis is carried out.The results show that after considering the traveling wave effect,the seismic response of the structure will increase or decrease to varying degrees.Among them,when the wave speed is 600 m / s,the amplitude of the seismic response change of the structure is the largest;After the isolation support,the seismic response at the control section has decreased to varying degrees,the structural rigidity distribution of the whole bridge is more uniform,and the stress is more reasonable.The fixed pier of the bridge is an unfavorable component.Therefore,the IDA analysis of the bridge pier is carried out,the linear regression equation of the corresponding damage index is established,the vulnerability curve is drawn,and the vulnerability analysis is performed.The results show that: under the site conditions of the bridge site,the bridge structure has a low probability of serious damage and complete destruction and good seismic performance.