Study Of Seismic Response Of Cable-stayed Bridges With Multipoint Excitations

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. Because of the long span, there exists the difference of seismic wave arrival time at diferrent bridge piers during an earthquake, which will have a significant impact on the seismic response of long-span cable-stayed bridges. So to study the seismic response of long-span cable-stayed bridges with multi-points exitation will be very important on the seismic design and to guarantee the seismic safety. In this thesis, the seismic rensponse analyses theory, the modeling methods and the analyses methods are discussed. The finite element method is used in modelling a concrete cable-stayed bridge with single cable plane and the dynamic characteristic are analysed. The seismic response of the example bridge are analysed with multipoint exicitation of EL Centro, Taft, Tianjin waves and Wenchuan earthquake waves. The camparison study is carried out with the seismic response with uniform exitation, and the inflence of mulitipoint exitation on the bridge is studied also. The main research work includes:1. The seismic damage and the reasons of bridges in earthquakes are discussed, the development of bridge earthquake resistance design methods are reviewed, the state-of-the-art of finite element modeling, input of the ground motion, and current situation of the multipoint exitation analysis of cable-stayed bridges are introduced systematically.2. The dynamic equations and the numerical analysis methods, the input of ground motion in time history analysis, the determination of damping ration 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 with single cable plane is established using the MIDAS/Civil program and the dynamic characteristics of the bridge are analysed.4. The seismic response of the bridge are analysed with multipoint exicitation of EL Centro, Taft, Tianjin waves and Wenchuan earthquake waves. The camparison study is carried out with the seismic response with uniform exitation, and the inflence of mulitipoint exitation on the bridge is studied also.