Study On Longitudinal Seismic Response And Isolation Measures Of Long Continuous Beam Bridge In High Intensity Area

In recent years,in order to meet the needs of economic and social development and improve the backward situation of traffic,our country has vigorously promoted the construction of traffic infrastructure.The long continuous beam bridge has the advantages of large overall stiffness,simple and beautiful bridge type,good mechanical performance,mature construction technology,good driving comfort and low cost.It is widely used in river crossing projects.However,there are many earthquakes in China,and some bridges are built in high intensity areas.Earthquake disasters have caused great loss of life and property.Under strong earthquakes,long bridge structures are more likely to be damaged to break the lifeline,resulting in more serious secondary losses and disaster relief difficulties.Therefore,it is particularly necessary to study the seismic response law and seismic isolation measures of long bridges.This paper is based on a long continuous beam bridge in high intensity area.The finite element nonlinear analysis software CSiBridge is used to establish the numerical analysis model,and the seismic response and isolation measures of long continuous beam bridge in high intensity area are analyzed and studied.The main research contents and conclusions are as follows.(1)The first chapter discusses the basis,purpose and significance of this paper,summarizes the research status and existing problems of seismic response of long continuous beam bridges and seismic isolation measures of bridges in high intensity areas in China and abroad,and clarifies the main research content of this paper.(2)For the project,the second chapter details the modeling of the finite element model.And this chapter discusses the influence of pile-soil effect,fixed bearing position and bearing constraints on the natural vibration characteristics of the structure from the aspects of frequency,period,vibration mode characteristics and modal mass participation coefficient.The analysis shows that the fundamental frequency of the structure decreases after considering the pile-soil effect;the setting position of the fixed bearing and the longitudinal constraint of the bearing only affect the low-order vibration mode,and the fixed constraint only affects the longitudinal vibration of the structure,which has little effect on other directions.The longitudinal horizontal thrust stiffness of the long continuous beam bridge is relatively small.(3)According to the nonlinear analysis theory,nonlinear categories and their sources,the third chapter gives the numerical analysis method of nonlinear problems,clear seismic wave selection principle and Rayleigh damping settings;in view of the seismic action of E1 and E2 in high intensity area,this chapter discusses the influence of material nonlinearity,geometric nonlinearity and pile-soil effect on the seismic response of long continuous beam bridge.The analysis shows that under the action of E1 earthquake,the structure does not enter the plastic state,so seismic analysis does not need to consider material nonlinearity;under the action of E2 earthquake,the structure enters the plastic state,so large error will be produced without considering the nonlinear effect of material.Geometric nonlinearity has little effect on seismic response of long continuous beam bridge under E1 and E2 earthquake,so it is not necessary to consider.Considering the pilesoil effect,the deformation of the structure increases and the internal force decreases.Without considering the pile-soil effect,the seismic response of the internal force of the structure is conservative,but the calculation efficiency can be improved.(4)According to the characteristics of long continuous beam bridge,the fourth chapter analyzes the effect of non-uniform excitation on structural seismic response.The smaller the apparent velocity of seismic wave is,the more obvious the traveling wave effect is,and the smaller the maximum bending moment at the bottom of fixed pier and the displacement at the top of pier are.The traveling wave effect should be considered for long continuous bridges.After considering the partial coherence effect,the internal force and deformation of fixed pier and non-fixed pier increase;after considering the local site effect,the internal force and deformation of the fixed pier decrease.In seismic response analysis of long continuous beam bridge in high intensity area,various non-uniform excitation effects should be considered.(5)For the seismic isolation measures of long continuous beam bridges in high intensity areas,the fifth chapter compares and analyzes the isolation efficiency of lead rubber bearing and sliding friction pendulum bearing,and studies the parameter sensitivity analysis and optimization of sliding friction pendulum bearing.The analysis shows that in the long continuous beam bridge,compared with the lead rubber bearing,the sliding friction pendulum bearing has better seismic isolation effect,smaller internal force and deformation of the fixed pier,and more uniform and reasonable force of the whole bridge.The friction coefficient of the friction pendulum bearing should be reduced as much as possible,but the curvature radius of the bearing has little effect on the seismic response of the structure.