Seismic Response Research Of Extradosed Cable-stayed Bridges

As a novel bridge structure style, Extradosed cabale-stayed bridge has a great development in recent years and is very competitive in domain of long-span bridges. International and domestic scholars have carried out in-depth study on extradosed cabale-stayed bridge and achieved many research results in the field of engineering practice. However, research results about dynamic characteristics of extradosed cabale-stayed bridge have achieved less, seismic performance particularly.Floating system,which is beneficial of seismic resistance, is not often applied in extradosed cabale-stayed bridge, consolidation and support systems are frequently choosed correspondingly. Extradosed cabale-stayed bridge has similar girder characteristics as continuous beam bridge, and its stiffness is much larger than conventional cable-stayed bridge.So, there are much difference between this bridge style and conventional cable-stayed bridge on seismic response characteristics. In this thesis, response spectrum method and time-history analysis mefhod are both adopted to analysis seismic response characteristics in frequent earthquake. The results of two methods are checked with each other, and the influence of foundation stiffness is considered. It is showed that, the force responses of pier are reduced, but the displacement response of tower increases, leading to increase the force response of tower bottom. Conclusion is that simulate foundation stiffness suitably will reflect the role of elastic foundation played in buffering the earthquake effect correctly.Plastic deformation are mainly concentrated in pier in rare earthquake, and if plastic hinge generates in some pier units, it will have a great effect on full-bridge seismic response, In this thesis, non-linear time history analysis method is choosed to research the seismic response under E2 earthquake, it is showed that bottom of pier generates plastic hinge, and the plastic destruction of these units can take advantage of hysteretic mechanism to absorpt part of earthquake energy, which will buffer seismic loads. But the displacement response of upper structure will be increased correspondingly, and the force response of tower bottom may have a tendency to increase under consolidation system. In this thesis, Midas / civil is applied to model and calculate seismic response results, and some recommendations are gived according to the relevant conclusions obtained.