Study On Seismic Performance Of High-pier Extradosed Cable-stayed Bridges

The extradosed cable-stayed bridge is a new bridge structure between continuous beam bridges and cable-stayed bridges.As compared with other bridge structures,the extradosed cable-stayed bridge has the advantages of beautiful appearance,convenient construction,economy etc.,and therefore it is more competitive in lone-span bridges.In recent years,the extradosed cable-stayed bridge is developing towards larger span and deeper pier.Based on the research work at home and abroad,it is found that the dynamic characteristics and seismic performance of extradosed cable-stayed bridges with high piers and long spans are relatively few.In this paper,the dynamic characteristics and seismic performance of the high-pier extradosed cable-stayed bridge are studied,which provides theoretical reference for the seismic design of the extradosed cable-stayed bridges.Firstly,the development status and trend,structure characteristics and research status of the extradosed cable-stayed bridges are introduced.Secondly,the theory and method of seismic response analysis is described.Thirdly,the finite element model of the the Hongxi bridge is established by MIDAS/CIVIL software,the reasonable completed bridge state and the dynamic property of the bridge are analyzed,and finally the seismic response of the bridge is investigated numerically by response spectrum analysis and dynamic time-history analysis respectively.Finally,the influence of structural parameters on the seismic performance of high-pier extradosed cable-stayed bridge is investigated.The research results show that:(1)The natural frequency of the high-pier extradosed cable-stayed bridge is relatively smaller as compared to the same span cable-stayed bridge,the fundamental period is long,and the longitudinal and transverse rigidity of the bridge is relatively weak.(2)Under the longitudinal and transverse earthquake actions,the seismic response of tower and girder are significant,the maximum internal force are produced at the pier bottom and the intersection between the pier and girder,and the maximum displacement appears at midspan and the top end of tower.Under E1 earthquake action,the bridge is in a linear elastic state,however under E2 earthquake action,structural nonlinearity has great effect on the seismic response of bridge,and therefore the nonlinear time-history seismic response analysis should be adopted.(3)In the case of reducing the side to main span ratio,the tower size,the segment length without stayed cables and increasing the pier size can effectively improve the seismic performance of high-pier Extradosed cable-stayed bridge.