Theoretical And Experimental Research Of Three-Dimensional Seismic Base Isolation System

As a new and effective method to withstand horizontal component of earthquake for building structure, the base isolation technique has been in the engineering application phase. However, for some important buildings and foundation facilities in the earthquake region, it is necessary to consider the effects of 3D aseismatic analysis including vertical component because the earthquake itself has multi-dimensional characteristics. We find that there has been no really improvement on three-dimensional isolation study till now. The lead rubber bearings with lead dish spring creatively presented here can be used to solve the three-dimensional isolation problem.The three dimensional lead rubber dish bearings(3DB) is composed of lead rubber beading in series with lead dish spring. The lead rubber bearing is used in horizontal isolation of earthquake while the lead dish springs bearing is in vertical isolation of earthquakes. The modal presented in this dissertation is effective in the resolution of difficulty in strong vertical capacity and vertical damper of three dimensional isolation bearings, effectively suppress the rocking motion as well. The 3DB is not only with three dimensional appropriate stiffness and damper performance, but also with easy stable performance and compact system, easy to manufacture as well. This 3DB has wider application future in 3D base isolation structure, and it can be also used in isolation of mechanical equipments.This paper creatively put forward 3DB design theory and analytical methods based on the intensive study of structural characteristics of 3DB. Moreover, the 3DB model is firstly designed and produced. 3DB stiffness and damping performance of the model is studied through the testing of static loading and dynamic loading. The study results go as follows: First, this 3D isolation bearing is with 3D appropriate stiffness and damping performance. Second, The ratio between static and dynamic stiffness is 1.3, with the increasing of loading frequency the yield force of 3DB, the pre-yield and damping ratio also increase, but the effects on the post-yield stiffness are not obvious.The paper fully analyses the seismic response of multiple earthquakes of 3D base isolation structure by using coupled lateral torsion particle model. First, on the basis of study on the structure of 3DB, some hypothesis and simplification are made to the upper structure and isolation system. Then, according to the uncoupling of horizontal and vertical earthquakes, the response to 3D earthquakes is separated into torsion coupling and vertical independent translation and motion equations set up accordingly. Finally, A L-shaped plan, five-story, 3D base isolation frame structure is designed, systematic analysis of response to 3D earthquake is offered and the effects on vertical isolation are studied. It is also found that the isolation structure with 3DB is effective in 3D isolation, it can lower 50% response of earthquake than non-isolation structure. Bi-lateral earthquake input and structure eccentricity have obvious effects on the horizontal displacement of isolation system, which can increase 30% than one-way input, 20% increasing than non- eccentricity structure. The study also points out that reduction of the stiffness is effective in decreasing the seismic response of structural earthquake before the vertical stiffness reaches the point of 2000kN/mm. The reasonable damping ratio of isolation system is about 20% to 30%.Finally, this paper analyses the response of multiple earthquakes by nonlinear, space, time-history analysis with the help of 3D FEM. The results go as follows: by adopting the 3D FEM model, the more complete and accurate results can be obtained and the analytical result is lower than particle model. The study also finds that the upper structure design method is likely to be safe if the intensity of aseismatic structure is lowered one step, at least with 30% safety buffering. So it is practically important to carry on the study on the whole structure of 3D FEM model. The creative t...