Study On Seismic Mitigation Of Large Span Steel Truss Bridge

The favorable force characteristics of the steel make it have a unique advantage in the long span bridge,and in the design of large span steel truss bridge,the seismic behavior of the structure needs to pay close attention.In this paper,a large-span continuous truss bridge is used as the research object.The full-bridge nonlinear finite element model is established by using SAP2000 finite element software to study the seismic behavior of these bridges under rare earthquakes.According to the stress characteristics of the structural seismic system,make two kinds of aseismic design.The parameters of the viscous dampers are optimized and the asesmic performence of viscous damper and the Lock-up device on the bridge structure under rare earthquakes is analyzed.The influence of traveling wave effect on the structure with viscous damper is studied.Based on the seismic ground motion parameter zonation by the fifth generation seismic ground motion parameter zonation map of China,the aseismic performence of viscous dampers in extremely rare earthquakes is studied.The main work of this paper is as follows:(1)Considered the geometric nonlinearity of the structure and the nonlinearity of the material,the nonlinear finite element model of the whole bridge is established by applying the finite element software of SAP2000,and the nonlinear time-history analysis method is used to analyze dynamic response of the long span bridge under rare earthquakes.(2)According to structural characteristics,we have made two kinds of aseismic design of the vertical bridge.The parameters of the viscous dampers are optimized and the aseismic performence of viscous damper and the Lock-up device on the bridge structure under rare earthquakes is analyzed.(3)Based on the condition of the project site,the multi-support excitation time-history analysis of the long span steel truss girder is carried out to future study the influence of traveling wave effect on the damping structure with viscous damper.(4)Based on the seismic ground motion parameter zonation by the fifth generation seismic ground motion parameter zonation map of China,the aseismic performence of viscous damper in extremely rare earthquakes is studied.The results show that the longitudinal direction of the bridge is the opposite direction of the seismic response,and floating of the main girder has a great influence on the seismic response of the structure;The viscous dampers with parameter optimization can significantly reduce the displacement of the main girder and can effectively reduce the internal force of fixed pier bottom.The Lock-up device is not ideal for aseismic performence of the main beam displacement and the internal force of fixed pier bottom.The effect of traveling wave on the long-span continuous truss bridge is not significant,and even has a beneficial effect on the partial structure.The aseismic performence of viscous dampers is better under the design ground motion and rare ground motion,and the internal force of fixed pier bottom under very rare ground motion is reduced.