Seismic Isolation Research Of High-Rise Chassis Frame Structure

As a kind of passive control system,building seismic isolation is able to reduce the structural seismic response of the earthquake by setting up isolation bearings. Seismic bearings are usually installed at the bottom of structures or between layers of upper floors,which is called base-isolation and storey-isolation.With the deep research of seismic isolation technology,base-isolation has formed a complete set of theory and has been widely used in the actual project while the storey-isolation is still at the beginning of development and needs further improvement.This paper describs the general situation of seismic isolation system survey and mechanical properties of isolation bearings at first, and then mechanical model of earthquake base-isolation and storey-isolation are established as well as the derivation of dynamic equilibium equation.In the end,anti-seismic,base-isolation and storey-isolation models of a frame construction with large podium which has two bottom stories and eight upper floors are built and analysed by use of large-scale structural finite element analysis software SAP2000.The storey isolation layer is setted at the bottom of the third floor column in the storey-isolation model.The analysis mainly contains modal analysis and dynamic time-history analysis. By use of EL-centro、Tangshan wave and Nanjing wave in dynamic time-history analysis,maximum story drifts and maximum storey shear force under frequently occurred earthquake can be worked out and the story-drift-angle of the lower part of the isolation layer under rare earthquake can be checked as well as the of drawing the acceleration time-history curve at the top of the building.The results show that,seismic isolation structure can effiently extend the free vibration period of structure,especially for first three mode. By making a comparison of the story drifts, storey shear force and story-drift-angle,it is easy to find that base-isolation and storey-isolation structure have much better effect in shock obsorbing and damping than anti-seismic structure.