Seismic Performance Analysis Of Long-span Cable-stayed Bridges With Isolation Bearing

Our country is located in the eastern part of Eurasia,western part of Pacific Ocean.For this reason,our country is one of the most frequent place in the world for earthquakes.With the development of bridge engineering,more attentions have been put to the design of long-span flexible bridge.Due to the good effect of seismic mitigation and absorption and easy repairability and replaceability,seismic isolation design is the hot issue in the field of anti-seismic.Bridge bearing isolation design has all the advantages of seismic isolation mentioned above.Since the invention,isolation bearing has been widely used in bridge engineering all over the world and has been proved useful.The cable-sliding friction aseismic bearing(CSFAB)is used as seismic isolation device in this article.In order to study effects of CSFAB,choosing a long span cable-stayed bridge as object of study.The main research content is as follows:(1)This article introduces the structure and working principle of CSFAB and analyzes isolation characteristics of CSFAB.Using a long span cable-stayed bridge as object of study and building fiinite element model of the bridge.Make sure the model's mass,stiffness and boundary conditions similar to actual structure as much as possible.(2)Carry on the self libration analysis to the bridge.In order to figure out the best way of arrangement form of CSFAB and the corresponding seismic mitigation effects,several different working conditions are set to be analyzed.The investigation result reveals that long span cable-stayed bridge belongs to long period structure and he CSFAB can reduce the pier-girder relative displacement effectively and can avoid of collision of adjacent girders.Therefore,it's better to arrange CSFAB in whole bridge.The result also shows that the internal force of towers,piers and cables increased in different degrees.Stayed cable's horizontal stiffness is very important to the balance of displacement and internal force.Pier-girder relative displacement will decrease,internal force of substructure of bridge,on the contrary,will increase if horizontal stiffness of stayed cable increases.So,it's necessary to adjust Stayed cable's horizontal stiffness according to physical truth.(3)In order to analyze the influence of pile soil interaction,corresponding finite element models are built.Soil and structure interaction is modeled by soil sping.The investigation result reveals that pile soil interaction can absorb earthquake wave's shocking which is beneficial to substucture of bridge,but it also magnify displacement of top tower.It also result in deformation incompatibility of bridge tower and girder.(4)Dynamic water's influence is simulated by added mass.The investigation result reveals that dynamic water will magnify bridge's seismic reponse.Therefore,the influence of dynamic water cannot be ignored.