Seismic Response Analysis And Vibration Mitigation Design For Partially Cable-Strayed Bridge With Three Towers

Partially cable-stayed bridge(short pylon cable-stayed bridge)has been considered as a new type of structure in recent years, which is characteristic of the concentrative layout of short pylons, rigid beams and cables. As for structural properties, partially cable-stayed bridge is between continuous girder bridges and cable-stayed bridges. With the rapid growth of the number and the span of cable-stayed bridge, more attention is paid to the response of the cable-stayed bridge in the earthquake.This thesis mainly introduces the analysis of seismic response of bridges used by the four theories-Static method, response spectrum method, dynamic time-history analysis and random vibration isolation method and the theoretical study by the status quo, theory and analysis. The thesis takes the SanjiaoGang Bridge in Shengsi County as a real engineering project, which is a prestressed concrete partition cable-stayed bridge with three towers and being constructed now. The author builds up an elaborate finite element model with MIDAS/CIVIL and makes an analysis to the bridge with two methods: spectrum response analysis and elastic time-history analysis of earthquake. This paper studies damped energy-dissipated earthquake-reduction design. The main content of this paper includes:(1) The free vibration characteristic of the bridge is studied, and the longitudinal, transverse, vertical and the maximum combined seismic response are analyzed by the means of the response spectrum analysis.(2) The spectral analysis is linear so the nonlinear factors cannot be taken into account. The dynamic analysis of the Bridge is calculated also with dynamic . time-history analysis considering the nonlinear factors. The earthquake response is gained according to the calculation results of the two methods. And non-uniform seismic excitation of traveling wave effects was focused on.(3) This paper proposes that viscous dampers are set between the piers and the girder. Effectiveness of viscous dampers on the partially cable-stayed bridge is studied using the computer program MIDAS/CIVIL. It's concluded that the use of viscous dampers can drastically reduce displacements and forces of the structure.(4) In this paper, the main design parameters are described. The effects of damper coefficient and velocity exponents on the seismic response of the structure are studied. At last, based on the results obtained, some suggestions about the design of viscous dampers in the partially cable-stayed bridges are presented.