Study On The Influence Of Supporting System On The Seismic Vulnerability Of Long Span Cable-Stayed Bridges

Long span cable-stayed bridges play an increasingly important role in the highway and railway transportation of our country,and gradually become an important part of traffic network.However,earthquakes occur frequently in recent years and the’5·12’Wenchuan earthquake warns us because the earthquake seriously threatens the safety of bridges.The long span cable-stayed bridges are extremely complicated and there is no comprehensive and reliable standard to follow,so the seismic vulnerability research urgently need to be carried out.Based on the above background and the structural characteristics of long span cable-stayed bridges that has been built,the thesis eatablishes SuTong Bridge model using OpenSees and analyses seismic fragility in longitudinal,transversal and vertical direction.The main contents of this dissertation are as follows:1. The state of studies on the seismic vulnerability of conventional bridge and long span cable-stayed bridge at home and abroad is summarized.Some urgent problems needed to be investigated are pointed out.The research method and process is introduced.2. The nonlinear finite model of long span cable-stayed bridge considering the cable sag effect,P-△ effect of pier and large deformation effect is built by using OpenSees.The incremental dynamic analysis is done after selecting earthquake ground motion.The damage index of peir and bearing are defined.3. The seismic vulnerability of floating system,vertical supporting system,elastic restraint system and the constraint of damping system of cable-stayed bridge in longitudinal direction is done.The damage probability of components is compared.The influence of different supporting system for component vulnerability is analyzed.4. The bearing failure mechanism under the transversal and vertical earthquake is discussed.The bearing failure probability is compared to find the most vulnerable one. The vulnerability of piers and tower in transversal and vertical direction is done and compared to find the most vulnerable components.5. The damage probability of piers and tower under the action of longitudinal, transversal and vertical earthquake is contrasted.The damage degree of different directions for cable-stayed bridge is analysed.