基础隔震结构中上部结构与隔震层的刚度比限值研究

以控制结构变形为目标，将上部结构刚度与隔震层刚度的比值定义为隔震刚度比，作为反映上部结构与隔震层协同变形特点的指标。假定上部结构的地震作用沿高度为矩形分布，在一般结构单质点简化方法基础上提出一种隔震结构动力分析的等效简化方法。进一步分析双自由度等效模型的刚度影响和动力特性，以隔震刚度比的形式解释了结构位移需求、位移分配函数以及隔震刚度比对结构抗震性能的影响。基于抗震性能，推导出结构位移需求与周期关系式、临界隔震刚度比表达式、最大和最小隔震刚度比限值表达式。选取不同结构高度、地震烈度、阻尼条件等计算了上部形式为框架、框-剪、剪力墙结构的三类隔震结构在罕遇地震作用下的隔震刚度比限值。结果表明，一般隔震结构的隔震刚度比限值不宜小于4，低多层隔震结构主要由最小隔震刚度比控制，高层隔震结构在特定条件下需要满足最大隔震刚度比限值。计算结果整理成表格可供设计参考。

Study on limit of stiffness ratio between upper structure and isolation layer in base isolation structure

The stiffness ratio of seismic isolation, defined as the ratio of stiffness of the superstructure to the isolation layer, is proposed to be an index for controlling structural deformation and showing the deformation characteristics of the upper structure and isolation layer. Assuming that the seismic force of the superstructure is in a rectangular distribution, an equivalent simplified method for isolation structure is proposed based on the simplified method of SDOF system in general. The influences of the stiffness and dynamic characteristics in TDOF system simplified model were analyzed, and the results shown in the form of the stiffness ratio explained the influence of the structural displacement demand, the displacement distribution function, and the stiffness ratio on the seismic performance of structure. Relationship between displacement demand and structure period, expression of critical stiffness ratio, formula of the maximum and minimum stiffness ratio limit were deduced in terms of the seismic performance. The stiffness ratio limit of three types of isolated structures（frame, frame-shear wall and shear wall structure in upper structure form）are calculated with different heights, seismic intensities and damping under rare earthquake. The results show that stiffness ratio limit to isolated structure should not be less than 4 in general; low-rise isolated structure is mainly controlled by the minimum stiffness ratio limit, while high-rise structures by the maximum stiffness ratio limit under specific conditions. The results of the calculation was compiled into tables for reference.