Seismic Response and Parametric Analysis of Inter-Story Isolated Tall Buildings Based on Enhanced Simplified Dynamic Model

Abstract

As a generalized version of the base isolation, the inter-story isolation has increasing applications in tall buildings due to its better adaptivity. Compared with the seismic response of the base-isolated building, that of the inter-story isolated building is more complex because it is affected by dynamic characteristics of the lower structure (LS), isolation layer (IL) and upper structure (US), which deserves the in-depth study. This study presents a comprehensive investigation on the reduced model and the seismic response of the inter-story isolated building. The equations of motion are established using modal displacements of the linear lower and upper structures, as well as the displacement of the isolation layer with the nonlinear hysteretic restoring force character. In light of the contribution of the generalized stiffness, a method of selecting the adequate participating modes of lower and upper structures is proposed. The nonlinear time history analysis of example tall buildings to seismic excitations shows that the reduced building model can provide accurate estimation for important seismic responses. Based on the reduced building model, the influence of dimensionless parameters including frequency ratio, mass ratio, damping ratio, second stiffness ratio (i.e. ratio of the post-yield over pre-yield stiffness) and the ratio of yielding force to total weight of upper structure on structural responses are investigated systematically. Finally, the equivalent linearization method being suitable for the base-isolated structure is evaluated for the inter-story isolated structure, and the filter effect of the lower structure is emphasized.