Study On Seismic Performance Of RC Frame Structures With Story Isolation Design For Metro Depot Cover

Due to the different functions of the upper structure and the lower structure,the vertical components of the subway cover are discontinuous,and there is a mutation of vertical stiffness at the transfer floor,which is not conducive to the seismic resistance of the structure.According to the traditional seismic design method,it is difficult to meet the use requirements in high intensity areas.If the interlayer isolation technology is applied to the subway superstructure,it can not only solve the problem of vertical stiffness mutation,but also reduce the seismic response of the superstructure and improve the overall seismic performance of the structure.Based on the upper cover project of a Metro Depot in Xi’an,this paper establishes the finite element model of the isolation structure of the upper cover of the metro and carries out the elastic-plastic time history analysis,studies the damping effect of the isolation design on the structure,puts forward the optimal layout scheme of the isolation bearing,and evaluates the anti collapse performance of the isolation structure through the vulnerability analysis,the specific work is as follows:(1)The paper introduces the important role of the development of the property on the subway and the application status of the story isolation technology in this kind of structure,the principle and application range of the story isolation technology,the simplified multi-particle model of the story isolation and the solution of the motion equation of the model.(2)Based on OpenSees,two finite element models of isolation and non isolation design are established.The story shear force,overturning moment and top acceleration of the two structures are compared and analyzed under earthquake fortification.The elastic-plastic deformation of the story isolation structure and the indexes of the isolation layer are checked under rare earthquake,the results showed: the period of the structure after isolation is obviously prolonged,avoiding the excellent period of the site;the isolation layer can effectively reduce the seismic response of the superstructure,but it does not play an obvious shock absorption effect on the substructure;in the rare earthquake,the indexes of the isolated structure between the lower layers meet the requirements of the specification.(3)Based on the simplified multi particle model of story isolation,this paper studies the optimal layout of lead rubber bearing,natural rubber bearing and viscous damper in isolation layer.The characteristics of isolation device are summed up as equivalent stiffness and equivalent damping ratio of isolation layer,and the proportion of lead rubber bearing in isolation layer is expressed by lead content,the results show that when different isolation devices are combined,it is recommended to use lead rubber bearing in isolation layer.The optimal equivalent damping ratio of seismic layer is 0.14～0.24,and the optimal lead content of isolation layer is 0.2～0.42.(4)The failure mode of story isolation structure is analyzed by IDA method.On the basis of IDA analysis results,the collapse resistance of story isolation structure is evaluated by vulnerability analysis,and the limit value of performance index of story isolation structure in limit state is improved.,the results show that: with the gradual increase of seismic intensity,the isolation layer first reaches the limit value of displacement,which leads to the collapse From the vulnerability curve,it can be seen that the damage probability of story isolated structure at each performance level is far less than that of non isolated structure.