Study On Seismic Time History Analysis Of Cable Stayed Bridge

The semi floating system of cable-stayed bridges has a relatively long basic circle along the direction of the bridge.In general,it belongs to the isolation system.Large seismic displacement will be produced under the action of seismic load.How to control the seismic displacement is one of the key problems in the seismic design.Different from the CIS bridges which adopt floating or semi floating systems,cable-stayed bridges normally adopt restraint systems with pier-beam,tower-beam consolidation.Under the action of seismic load along transverse bridge,Auxiliary pier and transition pier often fail to adopt ductility design because of small vertical pressure or large lateral dimension,so that the seismic design of side pier and its foundation is more difficult.This paper aims at two problems.Along the CIS bridge,the elastic constraints and damping constraints are set up between the towers and beams,and the damping effects of the two schemes are studied by comparison and analysis.Along the cross bridge direction,the design idea of vibration reduction is adopted.Under normal operation and small quake state,fixed constraints between piers and beams are used;under the action of large earthquakes,the fixed direction is allowed to "fuse",and the seismic isolation can be played.At the same time,damping device is set between pier and beam to reduce the relative displacement of pier beam.At the pier-beam along the transverse direction of the bridge between the set of hysteretic dampers and viscous dampers,by comparing the seismic response and transverse consolidation system,the damping effect of two kinds of scheme is studied.The results of the analysis show that: Along the CIS Bridge,the elastic constraints and damping constraints between the towers and beams can significantly reduce the seismic displacement response between the tower top and the tower beam.The elastic constraint scheme reduces the basic cycle of the structure,increasing the shear force of the tower,especially the bottom of the tower.The change of bending moment of the bottom of the tower and the decrease in the arm are related to the amount of shear increase.The damping constraint scheme has little influence on the vibration pattern of the structure,basically reducing seismic displacement by increasing structural damping and has an obvious damping effect on the tower shearand bending moment.The effect of two damping schemes on seismic response of side span cables is more obvious.Due to the influence of vertical seismic load,the seismic response of middle span cable is slightly worse.The damping effect of the damping constraint scheme is more universal.Along the cross bridge direction,hysteretic damper scheme and viscous damper scheme are essentially isolation design.They can not only reasonably control the lateral displacement of the main beam,but also significantly reduced the seismic internal force of the pier.They both have significant shock absorption effect.The two kinds of shock absorption schemes have little influence on the displacement of top,middle span and the body of the tower,and the internal force of the tower body.Seismic internal forces of side span cables are reduced by using a lateral shock absorption scheme.The seismic internal forces of the middle span cable are basically unaffected by the seismic isolation of the side span bridge pier.