| As a passive vibration isolation system, the base isolation technique is to set up isolation layer with little horizontal rigidity and certain damping between the base and the superstructure of the building, which can help prevent seismic energy transferring to the superstructure, increase vibration period and reduce the structural responses induced by earthquakes. As research continues, the base isolation technique is gradually applied in the irregular plane structure of the building according to the actual project need. Therefore, it is necessary to conduct researches on the seismic response of the irregular plane isolation structure to protect people ’ lives and properties. Taking a seven-story base isolation of the u-shaped frame structure as an example, the paper adopts the methods of theoretical analysis and numerical simulation to do the following researches.At first,this article expounds the basic concept of base-isolated structure,base isolation technology and its characteristics and mechanical properties of the lead rubber bearing,gives calculation formula for damping and horizontal stiffness,choose reasonable mechanics model of isolation bearing to set up dynamic analysis model of single-particle and multiple particle base isolation system and deduce the solution of the dynamic equilibrium equation of base isolation system. Then, the finite element analysis software SAP2000 is adopted to establish the equivalent model of irregular plane u-shaped structure.Based on the two projects with one only considering vertical bearing capacity and horizontal lateral arrangement of the isolation layer and another considering stiffness and mass center,the paper carries out the dynamic time history analysis on 8 degree and rare EL-Centro wave.Tangshan wave and artificial wave and make a contrast between the results and traditional anti-seismic design to judge the damping effect of irregular base-isolated structures and get the layout principles of irregular base-isolated structures.The results show that compared with traditional anti-seismic structure,the horizontal seismic response of irregular based-isolation structure significantly decreases. And the seismic response in project one which considers adjust the position of the rigid body and the center of mass is smaller than that in projecttwo and greatly reduce the torsional effect of irregular u-shaped structure. |
