INVESTIGATION INTO THE SEISMIC ISOLATION COEFFICIENT OF LRB BASE-ISOLATED STRUCTURES FOR STRUCTURAL DESIGN

In the current code for seismic design of buildings (GB50011-2010), the seismic action of the superstructure of a based isolated structure can be calculated by means of a horizontal seismic isolation coefficient. Different horizontal seismic isolation coefficients correspond to different fortification intensities for a superstructure after its base is isolated. Horizontal seismic isolation coefficients and mechanical parameters of isolation bearing are closely correlated, therefore, in this paper, the explicitly mathematical formulation between mechanical parameters of LRB (Lead Rubber Bearing) and horizontal seismic isolation coefficients are established by combining equivalent linearization and modal decomposition response spectrum methods, which can be used by structural engineers in the preliminary design of base-isolated structures. It is demonstrated through the parametric study that the fortification intensity of the superstructure with base isolation can be reduced by 1.5, compared with the case of without base isolation when the fundamental period of a superstructure is less than 0.6s; the fortification intensity of the superstructure after base isolation can be reduced by 1.0, compared with the case without base isolation when the fundamental period of a superstructure is in the range of 0.6s and 1.0s; the fortification intensity of a superstructure with base isolation can be reduced by 0.5 at most, compared with the case without base isolation when the fundamental period of a superstructure is greater than 1.0s.