Research On Seismic Response Of Large Span Hybrid Girder Cable-stayed Bridges

The large-span bridges damaged or even collapsed by earthquake can not only cause huge loss of traffic lines, resulting in paralysis of the traffic in earthquake regions and increasing the difficulty of the earthquake relief, but also increase the secondary disasters which will result in the loss of the life and property as well as indirect economic. Therefore, it is very important to study the seismic analysis for a large-span hybrid girder cable-stayed bridge with high main towers, broad spans, and complicated structures.Taking the proposed Hongshui River hybrid girder cable-stayed bridge (HRCB) with asymmetric structure as engineering background, the dynamic finite element model of the bridge was established by using finite element analysis software, and the dynamic characteristics and seismic performance were calculated and analyzed. This paper also explores the influence of the traveling wave effect and aftershocks on the performance of the force structure. The main work and conclusion are as follows:1. According to the structural features of the HRCB, the methods of soilpile interaction were discussed. The dynamic finite element model of the bridge was established and the dynamic characteristics analysis was completed. The results show that the bridge has closed modes and the first fifteen natural frequencies are all below1Hz.2. The response spectrum analysis and dynamic time history analysis are used to calculate and analyze the distribution of the internal forces, displacements and stresses of the structure which is under the El and E2seismic level with the combination of the longitudinal and the vertical and the combination of the transverse and the vertical. The results showed that the bridge is still in elastic state under the action of the E1level, the concrete cracks appear in local regions of girder and pier under E2level, which meet the basic requirements of repairable in weak earthquakes and no crash in strong earthquakes.3. On the basis of dynamic time history analysis method, the longitudinal displacements and internal forces under four kinds of velocity by considering the traveling wave effect on seismic responses of the HRCB are compared with those under consistent incentive.4. The method of the rigidity reduction is used to simulate the damage of the piers after the principal earthquake. The responses of the structure under the aftershock is calculated, then the displacements and stresses changes of the structure under E1level are analyzed and compared with those under E2level. The results show that the aftershock can almost damage as badly as the principal earthquake.