Study on the influence of stiffness-to- gravity ratio on the seismic performance of base-isolated high-rise building structures

Base isolation can effectively improve the seismic performance and earthquake safety reserve of structures. However, when it is applied to buildings with large aspect ratios, there are two main problems: isolation effectiveness and overturning resistance. This paper discusses and studies related issues from the perspective of structural stiffness-to-gravity ratio. Based on the pendulum model, a nonlinear dynamic differential equation is established, solved and analyzed, revealing the influence of stiffness-to-gravity ratio on isolation design control indicators. The limits of height-to-width ratio that meet different anti-overturning requirements, and proposing a method to quickly predict isolation effectiveness and anti-overturning performance based on structural stiffness-to-gravity ratio and height to width ratio are clarified and verified through three-dimensional finite element model analysis. The results show that: compared with the height-to-width ratio of the structure, the isolation effect is more affected by the stiffness-to-gravity ratio; for structures in high intensity areas and large height-to-width ratios, the stiffness-to-gravity ratio has a more significant effect on the isolation effectiveness and overturning resistance. Structures with different height-to-width ratios have a minimum stiffness-to-gravity ratio that can achieve the expected isolation effect and a maximum stiffness-to-gravity ratio that meets the corresponding anti-overturning performance requirements; there is a limit value of height-to-width ratio under the optimal suppression of the overturning effect of the structure. The stiffness-to-gravity ratio of the isolated superstructure is inversely related to its height-to-width ratio that meets the corresponding anti-overturning requirements. Compared with the finite element model, the bottom shear force deviation of the flat swing isolation model is 12%, and the interlayer displacement angle deviation of the upper structure is only 1.4%, which can better present the deformation characteristics of the rubber bearing isolation system under earthquake action.