Influence Of Multi-support And Multi-dimensional Ground Motion Excitation On Seismic Response Of Long-span Steel Truss Arch Bridge

In the west of China,earthquakes are frequent and intense,and the geological environment is extremely complex,most of which are high mountains and valleys.Steel arch bridge has become one of the preferred bridge types in mountainous areas due to its light weight,large crossing capacity and other advantages,especially suitable for V-shaped canyon areas.The seismic response analysis of long-span steel truss arch bridge in high-intensity seismic region is very complicated,which leads to the traditional seismic design concept can not meet the seismic design of this kind of arch bridge.Therefore,it is necessary to study the seismic response analysis of long-span steel truss arch bridge.In this paper,a 490 m long-span deck-type railway steel truss arch bridge is taken as the research object.On the basis of reviewing a large number of relevant domestic and foreign literatures and comparing relevant seismic codes,the influence of multi-support and multi-dimensional seismic excitation on the seismic response of the long-span steel truss arch bridge is studied by combining theoretical research and finite element analysis.This paper mainly studies the following aspects:(1)Based on the displacement input,the direct integration method is used to obtain the quasi-static reaction by static analysis and the total reaction by dynamic analysis.Taking the relative motion method as the basic theory,the dynamic reaction can be obtained by subtracting the pseudo-static reaction from the total reaction of the structure,thus providing an indirect method to separate the pseudo-static and dynamic components of the structure under multi-support excitation.(2)Taking a 490 m long-span steel truss arch bridge as the research object,the finite element software SAP2000 program was used to establish the spatial finite element model of the whole bridge,and the dynamic characteristics were analyzed to summarize the dynamic characteristics of the long-span steel truss arch bridge.(3)Taking the three-direction acceleration time history of El-centro wave,Taft wave and San Fernando wave as the input ground motion,the seismic response of the long-span steel truss arch bridge was analyzed in one-dimensional,two-dimensional and three-dimensional input,and the calculation results of multi-dimensional input were compared and analyzed.The influence of multi-dimensional excitation on the seismic response of the long-span steel truss arch bridge was studied.(4)Taking the X-direction displacement time history of El-centro wave,Taft wave and San Fernando wave as the input ground motions,the seismic response of long-span steel truss arch bridge under multi-support excitation is analyzed,and the influence of multi-support excitation on the seismic response of long-span steel truss arch bridge is studied.(5)The quasi-static and dynamic components of seismic response of long-span steel truss arch bridge under multi-support excitation are separated,so as to analyze the relationship among the total structural response,pseudo-static response and dynamic response under multi-support excitation,and further study the influence of multi-support excitation on the seismic response of long-span steel truss arch bridge.