Research On Parameters Of Isolation Layer Of Base Isolation Structure

The base isolation system is one of the most representative seismic technologies of today,and with the continuous maturity of theoretical research,the base-isolated structure has already had excellent performance in the earthquake process.In the baseisolated structure,due to the large difference between the horizontal stiffness of the isolation layer and the stiffness of the upper structure,the seismic isolation layer consumes a large amount of energy in the process of seismic action,which can effectively reduce the seismic response of the superstructure and keep the upper structure in elastic state.However,nowadays,the design method of the isolated structure still has some shortcomings,the influence of the stiffness relationship between the isolation layer and the superstructure on the overall structural performance is neglected during the design of the isolation layer,resulting in the structural performance is not optimal.In this respect,it is necessary to study the relative relationship between the upper structure of the isolation system and the isolation layer on the stiffness,and to explore the influencing factors of the performance of the isolation system,and provide reference for the design of the isolation structure,and provide reference for the design of the isolation structure.The main contents of this paper are as follows:Firstly,the simplified method of the superstructure of the base isolation structure is introduced,and the upper structure is simplified into a single-mass point model together with the isolation layer to form a two-degree-of-freedom system.The stiffness ratio is defined,and the particle displacement function of the simplified model is obtained based on the equation of motion of the two-mass model,and the displacement limit conditions of the upper structure and the isolation layer are given.The optimal form of the damage of the base isolation structure is defined,and the critical stiffness ratio is derived from this.Secondly,four base-isolated structures with different stiffness of the isolation layer were established by using the finite element software ETABS,the actual stiffness ratio of the four structures is obtained by calculating the equivalent stiffness of the upper structure.Vulnerability analysis was performed based on the IDA method to obtain vulnerability curve and collapse probability curves.The results show that the stiffness ratio studied in this paper will affect the damage form of the base isolation structure,and there is an optimal stiffness ratio.Finally,the influence of the selection and arrangement of the isolation bearing on the performance of the structure under the condition that the stiffness of the isolation layer remains unchanged is studied.Six isolation structures were established in three groups,the problems studied are the selection of isolation bearings,the optimal placement of the isolation layer bearings,and the eccentric arrangement of the isolation layer.The analysis results can provide reference for the design of the base isolation structure.