Study On Seismic Add-storey Retrofitting Of RC Frame With Inter-storey Isolation

China’s urbanization level is relatively low. There are a large number of existing low-rise buildings. In order to improve the land utilization rate, and avoid large-scale demolition and reconstruction, people tend to choose adding storey on exsiting buildings. Based on the theoretical research and engineering practice, a new method was proposed, which means seismic reduction by adding storey. In this method, the add-storey part is built above isolation rubber bearing. In this paper, effects and rules of ‘seismic reduction by adding storey’ are researched, and some suggestions for the improvement of isolation rubber bearing’s parameters are given.This study regards RC frame as the research object. 3+1, 3+2 and 3+3 add-storey models are established by analysis software. Considering the period difference between directly and seismic reduction add-storey structures, 6 different earthquake waves are chosen as the excitation for every model. After elastic-plastic time history analysis under rare earthquake in SAP2000, results and rules of seismic response are acquired, such as storey drift, plastic hinge, absolute acceleration and storey shear.It is found that seismic reduction by adding storey has ideal effect. For the part of existing building, storey drifts decrease 20% to 40%; absolute acceleration and storey shear reduce 10% to 20%. For add-storey structure, the reduction of seismic response could reach 50%. This add-storey method can effectively control the speed and depth of plastic hinge development. It can also effectively reduce the peak of displacement and acceleration time history; make the curve change more gently. Summarizing analysis results, it is found that seismic reduction effect is inversely proportional to rubber bearing’s stiffness. For add-storey strucuture, the more numbers of storeys adding, the seismic reduction effect is better. But the effect is not so obvious for existing part. Based on the analysis results, diameter of bearing, thickness of rubber layer should be increased, in order to meet the limit value of axial compressive stress and shear deformation. With these changes, structures can still maintain a good seismic reduction effect.