Seismic Response And Energy Dissipation Analysis Of Composite Isolated Structure

The base isolation is to extend the natural vibration period of the structure by setting some kind of isolation device between the foundation and the superstructure,which impedes the transmission of seismic energy to the upper part of the structure and thus reduces the seismic response of the structure.At present,the commonly used isolation systems include lead-core rubber bearing(LRB)isolation system,friction-slip bearing(FSB)isolation system and combined isolation system.Combined isolation is to combine two or more types of isolation devices together to form a new isolation system according to the characteristics of different isolation devices.The friction-slip bearing has the advantages of high bearing capacity and excellent energy consumption and the LRB can provide automatic resetting ability after the earthquake,then the combination of these two bearings is a common combined isolation type.The effect of earthquake on the structure is actually a process of energy transfer,transformation and consumption,the energy response of combined seismic isolation system under earthquake action directly affects the safety of structure.Therefore,by studying the input and consumption of energy at the time of earthquake,it is possible to more clearly recognize the influence of the change of the design parameters of the isolation layer on the shock absorption effect of the isolated structure,which has important guiding significance for the correct estimation of the seismic performance of the combined isolation system,as well as the design and application in practical engineering.In this paper,taking a six-story frame structure as example,the dynamic response of combined seismic isolation structures under earthquake action are compared and analyzed by SAP20000 software.Then the influence of two key design parameters,i.e.friction bearing ratio and friction coefficient on structural energy consumption are resended,provid a certain reference for the popularization and use of combined isolation technology.The main work contents are as follows:(1)The seismic reduction principle of base isolation and the mechanical properties of LRB and FSB are expounded,and the restoring force model of the composite isolation bearing studied in this paper are provided,The dynamic equations of the combined isolation system are analyzed and solved,which provides a theoretical basis for the subsequent simulation analysis.(2)According to the design requirements,three analysis models including traditional seismic structure,LRB isolation structure and combined isolation structure are established respectively.The natural vibration period,floor acceleration,inter-floor drift,base shear and other performance indexes of the three structures under the action of earthquake are compared and analyzed to verify the damping effect of the combined isolation system.In addition,the displacement calculation,tensile and compressive stress calculation and wind resistance calculation of the lead-core isolation system and the isolation bearing of the combined isolation system under rare earthquakes are carried out to ensure the rationality of the layout of the isolation layer.The results show:the bearing arrangement of the two isolation technologies meets the requirements of the specification,and the combined isolation system can achieve better damping effect than the lead-supported isolation system under reasonable arrangement.(3)Based on the analysis of the seismic response of the combined isolation system,from the energy point of view,taking the energy input and dissipation as two research points,and analyzing the effects of frictional pressure ratio and friction coefficient on the input energy and energy consumption ratio of the combined isolation system.The results show that when the friction bearing pressure ratio is 0.24～0.48 and the friction coefficient is 0.04～0.1,the combined isolation system can achieve better damping effect.