Study On The Isolation Performance Effect Of The Curved Surface Friction Pendulum Support Under The Near Field Vertical Ground Motion

With more and more near-field earthquakes being monitored,it is found that the vertical acceleration amplitude of near-field ground motions often exceeds expectations,which usually causes more serious damage to bridges.There is a certain relation between friction energy consumption of friction slippery isolation bearings and vertical bearing reaction force.Therefore,in order to ensure the safety of the friction pendulum isolation support during the action stage under near-field ground motions,and establish a more perfect evaluation system of the friction pendulum bearing isolation performance,it is necessary to study the isolation performance effect of friction pendulum bearing under the near-field vertical ground motions.In this paper,applying the numerical simulation to study the isolation performance of curved friction pendulum bearings and the seismic responses of bridge structures under different intensity and different strength of near-field vertical ground motions.The following main conclusions are obtained:(1)Under the action of the frequent intensity,the near-field vertical ground motions has little influence on the structural seismic response.Under the action of designed intensity and rare intensity,the near-field vertical ground motions has different influence on the structural seismic response.In most cases,the structural seismic response of the rare intensity is more significant than that of the designed intensity.(2)Considering the near-field vertical ground motion,with the increase of the ratio of the vertical acceleration peak and horizontal acceleration peak,the displacement of pier top and the moment of pier bottom of the structure increase not obviously,while the shear force of pier bottom has much improved in most cases.(3)Considering the near-field vertical ground motion,the near-field ground motion has a great influence on the absolute acceleration of the upper structure,and the effect is more obvious with the increase of the ratio of the vertical acceleration peak and the horizontal acceleration peak.(4)When the buffer device is applied before limit device of the friction pendulum bearing,the different near-field vertical ground motion strength has little effect on the shear force of the bottom of the pier,but when there has no buffer device,the strong strength of near-field verticalground motion has a little influence on the shear force of the bottom of the pier.It shows that when taking into consideration the near-field vertical ground motion,the friction pendulum bearing with buffer limit combination device has better isolation ability than the ordinary friction pendulum bearing without buffer device.(5)From the frequent intensity to the rare intensity,the energy of the ground motion input is increasing,and the accumulative energy dissipation of the support is also increasing.Considering the vertical ground motion,the accumulative energy consumption of the friction pendulum bearing decreases gradually,the energy dissipation of the support decreases 18.7%under the rare intensity when the vertical ground motion is taken into consideration.