| With the proposal and gradual improvement of self-centering bridge pier structures,it is possible to use the piers to provide rocking isolation under strong earthquake or rare seismic events,and the seismic resistance goal of self-centering is achieved through the self-weight of the bridge,the transmission of loads by the upper structure,and limiting devices(SMA rods or prestressed bars).Due to the setting of SMA rods,the horizontal lateral stiffness of the self-centering bridge piers is increased,which can protect the piers and reduce the horizontal displacement of the top of the piers.In recent years,this has become one of the research hotspots.The good seismic performance of self-centering bridge piers combined with the good energy dissipation ability of shape memory alloys has led to the proposal of a controlled rocking bridge pier based on SMA limits.Reasonable elements and constitutive relationships were selected in Open Sees software to establish models of unrestricted free-swinging,pre-stressed bar-limited controlled swinging,and SMA-limited controlled swinging bridge piers.By comparing and analyzing the three types of bridge piers through dynamic time history analysis,their influence on earthquake response was studied.The research content and main work are as follows:(1)Based on Open Sees platform,the dynamic analysis models of controlled swing of SMA with infinite free swing and prestressed tendon limit are established respectively,and the constitutive model of SMA with initial clearance is established.(2)The effects of the initial gap and initial pre-load changes on the seismic response of the pier top horizontal displacement and pier bottom bending moment under the controlled swing of the SMA limit under ordinary ground motion and near-fault ground motion are explored.The impact of the initial gap and initial preload on the seismic responses of free swing,prestressed tendon limit,SMA limit pier top horizontal displacement and pier bottom bending moment under normal ground motion and near-fault ground motion is compared and analyzed.Influence.The results show that under normal ground motion,with the increase of the initial gap,the horizontal displacement of the pier top of the SMA-limited self-resetting pier will increase,and the bending moment at the bottom of the pier will decrease.The initial gap increases by 40 mm,and the horizontal displacement of the pier top will decrease If it increases by 1%,the bending moment at the bottom of the pier will decrease by 3%;with the increase of the initial preload,the horizontal displacement of the pier top of the SMA-limited self-resetting pier will decrease,and the bending moment at the bottom of the pier will increase.SMA-limited controlled swing piers,compared with free-swaying bridge piers,SMA-limited controlled swing piers reduce the lift-off displacement and lift-off times of the pier,reduce the horizontal displacement of the pier top,and increase the pier bottom bend Moment;Compared with the limit of prestressed steel bars,the lift-off displacement limit is slightly worse,and the horizontal displacement limit of the pier top is slightly worse,but the bending moment at the bottom of the pier is reduced.(3)Under ordinary earthquake and near-fault earthquake ground motions,the influence of changes in SMA diameter,rod location,and number on horizontal displacement and bottom moment at the top of the pier was discussed.The research showed that under ordinary earthquake ground motion,an increase in diameter and number would reduce the horizontal displacement of the top of the pier and increase the bottom moment.The closer the location of the arrangement is to the end,the smaller the horizontal displacement of the top of the pier and the greater the discreteness of the bottom moment.Under near-fault earthquake ground motion,an increase in diameter and number would increase the horizontal displacement and bottom moment at the top of the pier.The closer the location of the arrangement is to the end,the larger the horizontal displacement and bottom moment at the top of the pier. |
