Seismic Response Analysis Of Long-Span Cable-Stayed Bridges Under Non-Uniform Excitation And Aseismatic Design

It is well kown that the long-span bridge is one of the most important traffic life line projects, once destroyed, it will lead to huge economic lost, and heavily influence to the earthquake disaster relief work and repair of disaster areas damaged in an earthquake. Therefore the correct and effeetive designs of earthquake resistance and shock absorption are of great importance to the safety of cable-stayed bridges.In making aseismic designs of cable-stayed bridge, the leading thinking is that, in the earthquake, the internal forces and displacement of the cable-stayed bridge are the smaller the better, however, under normal circumstances these two parties are often contradictory. Therefore if it is to make internal forces reaction small, it often has to pay the cost of larger 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 technique for the long-span bridge.In this thesis, the seismic response analysis and viscous damper control for the long-span cable-stayed bridges under non-uniform excitations are systematically studied, and the following creativity work and achievements are included,1) In this thesis, time-history analysis, random vibration analysis and response spectrum method are summarized, and each other's advantages and weaknesses are compared. The dynamic response of multi-point excitation in bridge engineering applications are studied and discussed.2) Taking a planned long-span cable-stayed bridge which main span is 392m(the second Daxie bridge) in Ning Po as the example. Based on finite element program ANSYS, the long-span cable-stayed bridge in the pile-soil-structure interaction, bridge deck system material, concrete allocation in side span, span layout and other factors on long-span cable-stayed bridge dynamic characteristics and variation of seismic response are discussed, which provide an important reference for seismic design and analysis of long-span cable-stayed bridges.3) The responses to multi-point response spectrum analysis, time-history analysis (including uniform excitation, wave passage effect, multi-support excitation) of earthquake about the second Daxie bridge No.3 design scheme were further analysed. The law of the seismic response under non-uniform excitation for the long-span cable-stayed bridge is explored.4) By damping program of installing the viscous damper between the main tower and the main beam, the seismic response of the cable-stayed bridge is researched using finite element program ANSYS. The results show that the use of viscous dampers can drastically reduce displacements and internal forces of the structure. At last, based on the results obtained, some suggestions about the design of viscous dampers in the long-span cable-stayed bridges are presented.