| This paper takes Huangshui River cable-stayed bridge in Xining as the research background.It is special that the main tower passes through the main beam vertically,and the gap between tower and beam is 2.5cm.There is a risk of pounding under earthquake.Based on this,this paper studies the seismic performance of the bridge comprehensively under the premise of considering bearing sliding friction and not considering bearing sliding friction,and establishes four analysis conditions according to the different locations of viscous dampers.The specific research contents are as follows:1)Established the full bridge model by CSI-Bridge finite element software,and analyzed its natural vibration characteristics.The low-order vibration modes contributes a lot to the dynamic response of this kind of bridge.2)Studied the pounding response between main bridge and its approach bridge under extremely rare earthquake,as well as the gap between tower and beam.The results show that the pounding response of the gap is significant without considering the influence of sliding friction and damper.While the main bridge and approach bridge do not pound.Considering the influence of sliding friction and damper at the same time,it can effectively reduce the pounding response of the gap.The best effect is to arrange dampers at the gap between the tower and beam,as well as on the side pier and main beam of the main bridge.The peak value of pounding force and relative displacement are reduced by 76% and 44% respectively.Only arranging dampers in the gap,the effect of damper is second.The peak value of pounding force and relative displacement are reduced by 68% and 39% respectively.Although there is no pounding between the main bridge and the approach bridge,the relative displacement can be greatly reduced by considering the bearing sliding friction and damper.This will reduce the pounding risk.3)Studied the internal force and displacement response of main tower under extremely rare earthquake.The results show that the longitudinal viscous damper can significantly reduce the seismic response of the main tower without considering the influence of sliding friction,the bending moment at the bottom of the main tower is reduced by 21%,and the displacement at the top of the main tower is reduced by 44%compared with the condition without damper.The seismic response of the main tower can be reduced effectively,only considering the influence of bearing sliding friction.Its bending moment at the bottom of the tower is reduced by 14%,and displacement of the tower top is reduced by 22%.The seismic response of the main tower is same when considering one factor and two factors.The main tower is not damaged under the action of rare earthquake.4)Studied the internal force and displacement responses of main piers under extremely rare earthquake.The results show that the seismic response of the side pier will be increased if only the longitudinal viscous damper is placed on the side pier,without considering the bearing sliding friction.Its bending moment at the bottom of the pier increases by 64%,and the displacement at the top of the pier increases by 71%,compared with the condition without damper.The longitudinal viscous damper of side pier has less influence on the lower pier,but more influence on the higher pier when considering the influence of sliding friction.The seismic response of auxiliary Pier will be underestimated without considering the influence of bearing sliding friction.The main bridge piers are not damaged under the action of rare earthquake.5)Under the optimal seismic isolation scheme,the optimal interval of viscous damper parameters is optimized by taking the collision response of tower and beam gap and the internal force and displacement response of main tower as optimization indexes.The results show that when the damping coefficient θ=6000～8000(k N·s/m)and damping indexα=0.2～0.6,the viscous damper has the best effect on this bridge. |
