A Study On Energy Dissipation And Seismic Isolation Measures For High-Pier Continuous Girder Bridges Using The Numerical Simulation Technique

With the rapid development of transportation facilities in China,the number of high-pier bridges is increasing,and the seismic performance of high-pier bridges in high-intensity areas is becoming increasingly important.In view of the flexible overall stiffness of high pier bridges,this paper analyses the effects of various aseismic measures with energy dissipation as the main factor,and investigation the advantages of combined seismic energy dissipation and seismic isolation measures.In this study,from the equal pier height model for bridges in flat terrain to the non-equal pier height model for complex rugged terrain,from the simplified model of Mass and Single Column to the numerical model based on a practical bridge project,from the ordinary ground motion input to the near-field pulse-like ground motion input,the distribution schemes of bearing and damper are discussed,and the parameters of isolation and isolation devices are optimized based on the non-linear time history analysis of energy dissipation and seismic isolation of high pier continuous girder bridge.It is found that:(1)When Friction Pendulum System(FPS),Fluid Viscous Damping(FVD)or combination of the two are used separately in simplified model of Mass and Single Column model,although they have certain effect on overall reduction and isolation of regular high-pier bridges,the advantages of combined one is not outstanding.Besides,the simplified model of Mass and Single Column can not reflect the non-linear response of different piers and different pier-beam connections,and the conclusion of parameter analysis is only suitable for some qualitative estimation and judgment.(2)FPS seismic isolation measures,Basin Rubber Bearing(GPZ)and FVD combined seismic energy dissipation and seismic isolation measures and FPS and FVD combined seismic energy dissipation and seismic isolation measures can all suppress El Centro motion to a certain extent in the bridge model of high piers with equal piers.Comparatively speaking,the combined seismic energy dissipation and seismic isolation measures have more advantages.(3)The maximum internal force response peak of the non-equal high pier model appears at the bottom of the highest pier,which is different from that of the equal pier high model at the bottom of the fixed pier;the ability of FPS to prolong the basic period of the bridge system is limited.Because both of the combined isolation and energy dissipation measures adopt FVD,the effect of suppressing the relative deformation of pier and beam and the displacement of beam is obvious;it is more advantageous to arrange FVD on the relative low pier.The internal force distribution between high and low piers is better than that of the reference scheme when different isolation and energy dissipation measures are adopted.(4)The combined seismic energy dissipation and seismic isolation measures have better suppression effect on different impulsive ground motions.Overall,the combined seismic energy dissipation and seismic isolation measure of FPS and FVD has more advantages.The analysis of El Centro motion amplitude shows that the greater the acceleration amplitude,the more obvious the effect of seismic isolation.(5)The magnification effect of near-field pulse-like ground motion on bridge deck displacement is obvious.Although the bridge deck displacement decreases after utilizing the combined seismic energy dissipation and seismic isolation measures,the absolute response value is still large.It is suggested that the expansion joint of bridge deck should be properly enlarged and the anti-collision device of bridge head should be strengthened in the high seismic intensity area.