| With the increasing of the span and the using of the flexibility cable, the cable forces have more and more important influence on the distribution of internal force of the whole structure system and they have become the key to control the forcing of the whole bridge. So, how to reasonably determine the cable forces to make the internal force state of the cable-stayed bridge rational has become the key point in the design of cable-stayed bridges. And also, 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 have the same importance.Firstly, the development situation, structural systems and structural characteristics of concrete cable-stayed bridge are presented in this thesis. Then the integrated finite element model based on a practical project is built up by using finite element software called MIDAS/CIVIL 2006.Secondly, the unknown load-factor method is used which takes the minimum stress of girder and tower in the finished state as the objective function to decide reasonable finished state, then the backward analysis-forward iteration method is adopted to determine the reasonable construction cable forces.Finally, the seismic response is calculated and analysed by means of the response spectrum analysis. In this part, the standard seismic response spectrum's long period and damping ratio are modified, and the modified spectrum curves with different values of damping ratio are input in longitudinal, transverse and vertical direction respectively, the result of the seismic response with different values of damping ratio of the bridge in three directions is studied and compared.Some conclusions are obtained in this thesis, and can be referenced in the design of long span cable-stayed bridges. |
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