Inelastic Response of Base-Isolated Tall Buildings under Nonstationary Winds: Response History Analysis and Statistical Linearization Approach

This study investigated uncoupled crosswind and alongwind responses of base-isolated tall buildings under nonstationary wind excitations. The base isolation system has hysteretic restoring force characteristics represented in the Bouc-Wen model, while the upper building is modeled as a linear elastic multiple-degrees-of-freedom shear building. The nonstationary story wind forces are modeled in terms of evolutionary power spectra. Response time-history analysis was performed to characterize the response statistics including mean, standard deviation (STD), and extreme value. This work included an analytical solution of nonstationary time-varying response statistics. The time-varying mean of alongwind base displacement is determined from the solution of the state-space equation. The time-varying STDs of both alongwind and crosswind responses were estimated from the statistical linearization with Gaussian assumption combined with evolutionary spectra analysis. The numerical examples show that the transient effect of nonstationary excitations declines when yielding becomes significant, which leads to an increase in system damping. In the case of alongwind response, the transient effect on the time-varying mean of base displacement is more significant. This study not only presents an effective analytical approach but also sheds new insights toward improved understanding of inelastic responses of base-isolated tall buildings under nonstationary winds, contributing to a safer and more economical design of base-isolated tall buildings.