Dynamic Analysis Of Lead Rubber Structure In Vertical Seismic Action

Structure isolation is a new technology appeared in the process of reduceing response of earthquake, which sheds some lights on design of the seismic resistance to some special or important building. Isolation structure have stand a lot of test in the earthquake happened in recent years.The fact have indicated that the isolation structure have a good performance of isolating horizontal seismic effect. The existing isolated structure only considered the horizontal isolation effect, ignoring the influence of vertical seismic action. But according many earthquake damage,in many cases,vertical seismic effect may even exceed the horizontal seismic action, becoming the main reasons causing construction damage.Therefore, it is essential to study the dynamic characteristics of vertical seismic action on the whole structure.In this paper, the dynamic characteristics of base-isolated structures and mid-story isolation structures under vertical seismic action are studied.First, establish vibration equation and dynamic analysis model of base-isolated structures and mid-story isolation structures; then by using random vibration analysis method,deduce an analytic expression of the displacement response between superstructure and substructure when vertical harmonic loads carried on these two kinds of structures, and draw amplitude frequency curves of these two structures and different parameters respectively;At the last, analyse the variable parameters in the expression, summary the working mechanism of the base-isolated structures and mid-story isolation structures under vertical harmonic loads.In this paper, a five-story frame structure library taken as a research object, and the isolation effect and seismic response characteristics when adopted base isolation technology,story isolation technology, and traditional method of earthquake resistantance were studied.A finite element analysis software——SAP2000 was used to set up a 3d simulation model to analyse the seismic response of this library.During the compute process, LACC-NOR wave and Tianjin wave were chosen as the vertical earthquake input motions at these three models, study the structure's response of two cases--frequently occurred earthquake and rarely occurred earthquake. After a lot of calculation, analysis and comparison, some useful conclusions are obtained:the base-isolated structures and mid-story isolation structures can not reduce the response of vertical seismic actions, on the contrary, will amplify the response.Furthermore, if position of the isolation moves down,this amplification will be more obvious.Isolation structure can reduce the response of horizontal earthquake, but at the same time can amplify the vertical seismic response. So we must be fully consider it during the design of the seismic-isolation structure.