基于结构设计的LRB基础隔震结构水平向减震系数研究

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

现行的建筑抗震设计规范(GB50011-2010)中隔震结构的上部结构地震作用计算采用水平向减震系数的方法,不同的水平向减震系数对应着隔震后上部结构水平地震作用所对应的烈度分档。由于水平向减震系数与基础隔震系统的力学性能参数密相关,但对于两者之间的变化规律所开展的研究较少。该文以目前国内外最为普遍的LRB基础隔震结构为研究对象,通过等效线性化和振型分解反应谱方法,建立起了LRB隔震系统力学性能参数和上部结构地震作用的水平向减震系数之间的数学关系式以及计算方法,提供给工程设计人员用于基础隔震结构的初步设计过程之中。通过参数研究发现:上部结构自振周期小于0.6s,可以实现隔震后上部结构的水平地震作用比非隔震时降低一度半,上部结构自振周期介于0.6s^1.0s之间,可以实现降低一度,上部结构自振周期大于1.0s,最多可以实现降低半度。

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.