Research On The Design Method Of Large Floor Multi-tower Seismic Isolation Structure

For multiple single seismic isolation buildings that are adjacent but not connected,the design method of sharing the roof of the seismic isolation layer can be adopted to form a seismic isolation structure with a large floor and multiple towers,which can effectively reduce the design requirements of seismic joints.The connecting plate between the towers in the seismic isolation structure of the large floor multi-tower plays the role of coordinating the structural deformation at both ends,transmitting and distributing the horizontal force,and the difference in the dynamic characteristics of the structure at both ends will cause the connecting plate to produce a large additional force,resulting in local failure of the floor,which in turn changes the dynamic characteristics of the structure and affects the transmission of horizontal force between the towers.In this paper,the force influencing factors of the connecting plate between the towers and the design method of the floor are mainly studied.The main research results are as follows:(1)Based on a simplified mechanical model of the seismic isolation structure of a multi-tower with a large base plate,the effects of the differences in dynamic characteristics of the towers,the stiffness of the connection plate and the stiffness of the seismic isolation layer on the forces in the connection plate between the towers are analysed,and a seismic isolation design method to reduce the forces in the connection plate is proposed.The results show that in practical design,the force on the connection plate is mainly related to the period ratio of the tower after seismic isolation and the eccentricity of the seismic isolation layer,and the internal force on the connection plate increases with the increase of the period difference and the eccentricity of the seismic isolation layer of the tower after seismic isolation.When the seismic isolation period ratio of the adjacent towers is 1 and the mass centre of the superstructure coincides with the stiffness centre of the isolation layer,the stiffness of the isolation layer should be reasonably distributed during the seismic isolation design so that the stiffness ratio of the adjacent structure is equal to the mass ratio of the superstructure,and the eccentricity of the isolation layer is verified to meet the code limits.(2)The seismic performance objectives of the floor are discussed,and the design and bearing capacity verification method of the floor reinforcement based on the main stress are proposed based on the characteristics of the in-plane force of the bottom plate,and verified by the large-scale elastoplastic analysis based on the engineering case.The results show that the floor plate designed according to the main stress can meet the performance targets of each seismic level,and in rare earthquakes,only minor damage occurs at the position of the connecting plate,and the bottom plate does not fail before the superstructure.(3)The stress distribution characteristics of the large floor under the action of earthquake are analyzed,and the calculation method suitable for the stress analysis of the floor is discussed.The results show that under the action of horizontal earthquake,the stress of the connecting plate is significantly higher than that of the floor directly below the tower.The mode shape decomposition reaction spectrum method will underestimate the stress of the connecting plate,and the time history analysis method needs to be used for supplementary calculation.