Seismic Response Analysis Of A Long-Span Steel Truss Girder Highway-Railway Cable-Stayed Bridge

It is well kown that the long-span bridge has an important position in the traffic engineering. If it was destroyed in the earthquake, it will lead to huge economic loss, and heavily block to the earthquake disaster relief work in an earthquake. Therefore,in consideration of aseismic and shock absorption design of long-span cable-stayed bridge has a very important meaning.At the time of making aseismic designs of cable-stayed bridge, it is hoped that,in the earthquake, displacement and internal force of structure response of bridge are the smaller the better, However, this is hard to achieve with conventional methods. Because the structure’s internal force decreases, it will cause the increasing of displacement, and vice versa.The installation of viscous dampers in the long-span bridges can’t increase the stiffness of the structure. At the same time, it can reduce the seismic responses of the long-span bridge, because viscous dampers can consume a lot of energy created by earthquake. So it is an ideal shock absorption measure for the long-span bridge. Viscous damper in bridge structures will not cause changes in stiffness, it can pass on the dissipative structure of earthquake input energy to control vibration response of bridge structure.lt is an ideal shock absorption measures of bridge.The content of this theses as follows:(1) According to Shanghai-Nantong Yangtze River Bridge project, establishing the finite element model of the bridge,as well as calculating the dynamic characteristics of structures, and then analysis.those characteristics to get the laws of the dynamic characteristics of the bridge.(2) Using response spectrum method to analysis the bridge, According to the China railway engineering seismic design code and considering the geological data of the bridge,then should select an appropriate response spectrum curve to research different component combinations of internal force and displacement of the earthquake response.(3) Getting result of time-history response analysis of bridges to draw bridge internal force and displacement responses;Comparison of time-history analysis method and response spectra calculation results to tell the analysis on dynamic response of bridgeswhether it is coherent;and also researching the influence of wave passage effect on seismic response of bridges.(4) Based on seismic design of long-span cable-stayed bridge, setting a flexible interface and viscous dampers to reduce the displacement of the top of bridge tower. The analysis will be presented in the following two aspects:different elastic stiffness and damping effect on the vibration-isolating effect of two devices, and to compare both the damping effect of vibration reduction mechanism.