Study Of Three Dimensional Seismic Response Of Concrete Cable-stayed Bridges

Long span cable-stayed bridges generally are the key structures of transportation system. Great direct and indirect economic loss will be caused if these bridges get damaged in an earthquake. Therefore the correct and effective earthquake resistance design and assurance of earthquake safety of cable-stayed bridges are of great importance. The finite element modeling methods and nonlinearities of cable-stayed bridges are discussed in this paper, and the dynamic characteristic and seismic response are carried out based on a concrete cable-stayed bridge with single cable plane. The main research work includes:1. The seismic damage and the reasons of bridges in earthquakes are discussed, the development and changes of bridge earthquake resistance design are reviewed, the state-of-the-art of finite element modeling, input of ground motion, and time history analysis of cable-stayed bridges are systematically introduced.2. The dynamic equations and the numerical analysis methods, the input of ground motion in time history analysis, the determination of damping ration, and the geometric nonlinearity and material nonlinearity of cable-stayed bridges are discussed in detail.3. The modeling method of cable-stayed bridges is studied, and the 3-D finite element analysis model of a concrete cable-stayed bridge is established using the MIDAS/Civil program. The dynamic characteristics of the bridge and the influence of different longitude constraints to the dynamic characteristics are studied.4. The seismic response analysis is conducted to the cable-stayed bridge with El Centro, Taft and Tianjin earthquake records. The seismic responses with different earthquake input and the linear and nonlinear response are studied. Some conclusions are obtained in this thesis, and can be referenced in the seismic design of long span cable-stayed bridges.