Seismic Analysis Of Long-span Composite Cable-stayed Bridge

Large-span composite cable-stayed bridge is a very promising type of bridge,which plays an increasingly important role in transportation network.Therefore,it is necessary to study the seismic response characteristics and seismic performance of this type of bridge.In this paper,the seismic response characteristics and seismic performance of a 720 m long-span composite cable-stayed bridge were studied:(1)The response characteristics of the cable-stayed bridge under E1 and E2 earthquakes were studied by elastic-plastic dynamic time history analysis,and the influence of pile-soil interaction was evaluated;(2)The longitudinal displacement response of the cable-stayed bridge was reduced by installing viscous dampers in the longitudinal direction between towers and beams.The influence of the change of damping index and coefficient on the longitudinal seismic response of the cable-stayed bridge was studied.(3)The influence of traveling wave effect on the seismic response of cable-stayed bridge was studied by Large Mass Method.Six kinds of wave velocities,140 m/s,250 m/s,500 m/s,1000 m/s,2000 m/s and?m/s,were adopted respectively,which basically cover the ground and soil conditions from soft soil to hard rock.The results show that the longitudinal stiffness of the cable-stayed bridge bearings is very small when the longitudinal floating scheme is adopted,and the longitudinal displacement response of the bridge should be paid more attention to.For the seismic response of the tower,the internal force of the bottom section is the largest,so the degree of plastic hinge of the bottom section should be evaluated under the rare earthquake action.The pile-soil interaction can not only increase the natural vibration period of the structure,but also increase the damping of the system,which has a great influence on the seismic response of the structure,and should be considered in the design and analysis.Setting viscous dampers in the longitudinal direction between towers and beams can effectively control the displacement response of bridges,but the parameters of dampers have a great influence on the displacement and internal force,so parameter optimization analysis should be carried out.For the traveling wave effect,when the wave velocity is small,that is,the corresponding soft soil,it has a greater impact on the seismic response of cable-stayed bridges,so it should not be ignored.However,the effect of traveling wave is not significant when the wave velocity is large,that is,the hard ground.The purpose of this paper is to provide reference foraseismic design and analysis of this type of bridge.