Study On Reasonable Seismic System And Seismic Isolation Measures Of Composite Girde Cable-stayed Bridge

Composite girder cable-stayed bridge,which is composed of steel girder and concrete deck,has been widely used in the construction of long-span bridges with good mechanical properties.Based on the finite element theory,this thesis takes the Xigu Yellow River Bridge(177+360+177)m,a long-span cable-stayed bridge,as the research object,and adopts the nonlinear time-history analysis method to conduct the numerical simulation calculation for the cable-stayed bridge with reasonable seismic system and seismic isolation measures.The research of the thesis mainly includes the following aspects.1?The development of cable-stayed bridges and bridge seismic isolation systems at home and abroad were summarized,and the status quo and existing problems of long-span cable-stayed bridges were reviewed.2?Taking a long-span cable-stayed bridge as the research object,the finite element model of the whole bridge was established by using ANSYS and the dynamic characteristics of the structure were analyzed.Then,nonlinear time-history analysis was used to calculate the seismic responses of bridge structures under E1 and E2 seismic actions with longitudinal and transverse seismic inputs.The results show that the main beam displacement is basically uncoupled under the action of longitudinal earthquake and transverse earthquake.Besides,the response of bending moment of tower bottom under transverse + vertical earthquake is slightly larger than that under longitudinal + vertical earthquake,while the bending moment of pier bottom of transition pier and auxiliary pier is basically the same under two working conditions.3?In this thesis,the seismic system of bridges was summarized,and the modeling methods of ductile seismic system and seismic isolation system were introduced.In view of the weak seismic links of bridges,the longitudinal seismic responses of bridges with semi-floating system,ductile seismic system and seismic isolation system were compared.The results show that the ductile seismic system amplifies the displacement of pier top and main beam,and produces hysteresis rings at the bottom of the pier to dissipate the seismic energy,thus reducing the internal forces at the bottom of each pier.The liquid viscous damper in the seismic isolation system significantly reduces the displacement of the pier and the main beam,and the seismic response of each pier is relatively small.4?Based on two kinds of seismic isolation measures,the numerical study was carried out,and the arrangement of fluid viscous dampers and the application of the hybrid seismic isolation device based on friction pendulum bearing and fluid viscous damper on the long-span composite girder cable-stayed bridge were discussed.Furthermore,the influence of the bearing parameters on the seismic response of the cable-stayed bridge and the damping effect of the seismic isolation device on the bridge were analyzed,which provides a reference for the seismic isolation design of the same type of bridge in the future.