Application Studies On Base-isolated Structure With Laminated Rubber Bearings

After the'5.12'earthquake, base-isolated structure with laminated rubber bearings has been vigorously promoted in reconstruction, however, that most domestic engineers are not very familiar with it and lack of isolation analysis and design software make it difficult to be designed, also the further application of isolated structure is hindered.With the aim of solving those problems above, some researches, completed by author's experience in designing three isolated structures in Wenchuan earthquake area, are as follow: firstly, the mechanical properties of laminated rubber bearing (LRB), method for isolated structure analysis, common method for isolated structure design and some details are discussed; then, the assistant analysis and design software, called BAIS V1.0, has been prepared. It estimates seismic reduction effect, provides the layout scheme of bearings and checks that effect by ETABS; at last, the contrasting analysis and design of a constructed structure is completed by BAIS V1.0.From those researches, the following conclusions are drawn:â‘ The advantages of BAIS V1.0 in isolation analysis and design are as follow: before checking the seismic reduction effect by time-history analysis, bearings'layout can be adjusted, according to the result estimated by BAIS V1.0. So, the pass rate of checking can be improved and the period of design can be shortened; because of using ETABS for checking, the problem that losing members internal force, caused by muti-mass model, can be solved, and the real damping behavior can be given to LRB, which does better than equivalent linear method.â‘¡By testing in practical engineering, the seismic reduction factor and the displacement of isolation layer, simply calculated by BAIS V1.0, approach to those calculated by time-history analysis. It can be found that BAIS V1.0 is applicable to estimating the seismic reduction effect and guiding the isolation design.â‘¢The dynamic response of the structure under frequently occurred earthqyake (including story shear, story drift and the absolute acceleration of top floor) , can be decreased by isolation and the seismic reduction effect is significant. Under seldomly occurred earthqyake, the isolated superstructure can keep elastic character, which makes it applicable to lifeline engineering. With the peak value of ground acceleration grows, the seismic reduction effect of isolated structure becomes more significant.â‘£The base shear calculated by isolation model is seventy percent of that calculated by earthquake-resisitant model, whose earthquake fortification intensity is reduced by one level. So, if the isolated structure is regarded as the earthquake-resisitant structure, with the intensity reduced by one level, the earthquake force and the reinforcement design could be got, by mode-superposition response spectrum method. However, those results might be a little safter.