The Seismic Response Analysis Of Long-span And Suspension Bridges

Every earthquake disaster brought great damage to the safety of life and property for people. The more prosperous the cities and the society became, the more damage earthquake disaster brought. If the bridges which looked as very impertant structures by people for connecting with people's life collapsed caused by earthquake,the indirect disaster will take up to bring more loss of life and property. Now, we usually employ the response spectrum analysis which is defined in the earthquake-resistance code for bridge design. In fact, the different supporting points bear the variant earthquake motion which are produced by variant hypocenter, earthquake wave propagation path and ground, so the response of the long-span suspension bridge under the nonconforming stimulating of the earthquake was also necessary.In this thesis,I mainly consider the three aspects in earthquake analysis:the ways of earthquake inputing,the bridge's characters,bridge's earthquake response. Considering travelling-wave earthquake response were studied as follows on the basis of the study achievements at home and abroad and on the basis of one long-span and suspension bridge.⑴The study of analysis approach of earthquake response. Several analysis methods used to calculate the earthquake response of bridges,such as the time-history approach,the response spectrum approach,random vibration approach,are introduced and discussed.The practical application of dynamic balance equations of multipoint excitation are studied and discussed in this paper;⑵The finite element model of the structure was formed through reasonable simplification. And structural dynamic properties were calculated by using the famous program of ANSYS. Structure dynamic properties were performed;⑶The responses to uniform excitation of earthquake about the long-span and suspension bridge were analysed. Structural seismic responses that seismic wave was inputed from longitudinal direction,longitudinal and vertical directions,three directions were discussed. Internal forces and displacements of structural crucial sections were compared. Some beneficial conclusions were gained;⑷The responses to travelling-wave effect of earthquake about the long-span and suspension bridge were analysed. In the study,the contrast of the nonuniform multpiont excitation to uniform excitation,the conclusion is that the travelling-wave effect is very important for the long-span and suspension bridge.①The different wave speeds produce variant effects.In general,the litter is the wave speed,the bigger effect is the internal force and displacement,but the different wave speed cause the different effect.And between different waves delay phenomena is occurred.The time is decided by the direction of the transmiting earthquakes wave and the distance of the supporting points.②It is very obviously that bridge internal force and displacement have great change caused by travelling-wave.The effects are very obvious in amount.The responses to travelling-wave effect of earthquake benefits to the internal force of the main towers,but it is bad for the main beam.