Study On Seismic Performance Of Combined Isolation System In High-rise Building

The base fixed structure consumes seismic energy through the plastic deformation of structure,and the base isolation system makes use of the energy dissipation device of the isolation layer to achieve this purpose.Therefore,more and more attention has been paid to the design concept of base isolation,and the theoretical research and engineering practice of isolation technology have been developed rapidly.Taking the regular and irregular high-rise frame structure as the research objects,modal analysis and nonlinear time history analysis of three kinds of structural systems,such as base fixed,lead rubber isolation and combined isolation system are carried out by SAP2000.The isolation effect of combined isolation system in high-rise buildings is discussed.The main conclusions are as follows:(1)The modal analysis shows that the self-vibration period of the lead rubber isolation and the isolated structure is prolonged by 1.61 times and 1.71 times,respectively.which makes the site excellent cycle and the vibration period of structure is quite different,the possibility of resonance is reduced.Analysis of vibration data shows that the superstructure of the isolated structure is almost horizontal movement.There is a displacement mutation in the isolation layer.The relative displacement between floors is very small,while the fixed base structure due to the superstructure and foundation rigid,so the relative displacement between floors is larger,showing the shape of shear deformation.(2)Nonlinear time-history analysis of regular high-rise frame structure under frequent and rare earthquakes shows that compared with the fixed base structure the peak value of the top-level acceleration of the isolated structure,interlayer displacement of the upper structure layers and interlayer shear force decreased obviously,among which the combined isolation system has the most obvious effect.This shows that the isolation bearing has a filtering effect,so that part of the seismic wave components cannot be transmitted to the superstructure,greatly reducing the dynamic response of superstructure under the earthquake.It is possible to reduce the interlayer shear force of the combined isolation structure by increasing the number of ordinary rubber isolation bearings in the middle column,reducing the friction coefficient of the friction sliding bearing,reducing the yield shear coefficient and increasing the structural damping ratio,thereby further enhancing the isolation effect and reducing the earthquake disasters.(3)Nonlinear time-history analysis of irregular high-rise frame structure under the influence of frequent and rare earthquakes shows that the period ratio of the base fixed structure,lead rubber isolation and the combined isolation structure system are 0.88,0.84 and 0.81,respectively,among which the displacement ratio is less than 1.2,which can meet the specification requirements.Compared with the base fixed structure,the interlayer shear force and interlayer displacement angle of the isolated structure are obviously reduced,and the effect of combined isolation system is the most ideal.It can be seen that the combined isolation system also has a good damping effect on the irregular high-rise frame structure.