Inelastic Performance of High-Rise Buildings to Simultaneous Actions of Alongwind and Crosswind Loads

Abstract

Current tall building design to ultimate wind loads is based on a linear elastic design framework. The adoption of a performance-based wind design framework for tall buildings explicitly requires evaluation of building performance under various levels of wind hazards, including inelastic response. This study presents a comprehensive characterization of inelastic response of tall buildings under simultaneous actions of both alongwind and crosswind loads using a fiber-based three-dimensional (3D) nonlinear finite-element (FE) model of a 60-story high-rise steel building. The statistics of inelastic responses in terms of building displacement, acceleration, interstory drift, and base bending moment and member forces are quantified through response history analysis at different wind speeds. The inelastic building responses under alongwind and crosswind loads acting separately are also calculated and compared. The inelastic response is also compared to the elastic response of the corresponding linear building model. The yielding causes building drift in the alongwind direction that leads to increasing time-varying mean displacement. The development of drift is affected by fluctuating alongwind and crosswind responses. The steady-state value of drift is determined by the mean load and second stiffness in the alongwind direction. On the other hand, the fluctuating alongwind and crosswind responses can be quantified regardless of the mean load and time-varying mean response. The yielding leads to a reduction of fluctuating responses due to additional hysteretic damping. The second-order P-Delta effect on both elastic and inelastic responses is also examined. Finally, the influence of material yield stress is investigated, and the inelastic response is discussed in nondimensional quantities. The results of this study reveal the importance of consideration of simultaneous actions of both alongwind and crosswind loads for inelastic response analysis. The inelastic crosswind response affects the alongwind inelastic response. It particularly results in increased time-varying mean alongwind displacement, which contributes to building collapse when the second-order P-Delta effect is considered.