Top-Story Softening for Enhanced Mitigation of Vortex Shedding-Induced Vibrations in Wind-Excited Tuned Mass Damper Inerter-Equipped Tall Buildings

Abstract

An innovative structural modification, top-story softening, is herein proposed in conjunction with an optimally tuned top-floor tuned mass damper inerter (TMDI) for improved serviceability performance in typical core-frame slender buildings with rectangular floor plan susceptible to wind-induced vortex shedding (VS) effects causing occupant discomfort. This is supported through formulating a novel optimal TMDI tuning problem in which TMDI inertial properties, i.e., attached mass and inertance, as well as the lateral top-story stiffness are design parameters aiming to minimize peak acceleration of the highest occupied floor. The optimal TMDI tuning problem is numerically solved for a wide range of design parameters for a 34-story composite core-frame building subject to stochastic spatially-correlated wind-force field accounting for VS effects. A low-order dynamical model capturing faithfully modal properties of the case-study building is developed to facilitate computational work and parametric investigation. It is found that top-story softening reduces attached TMDI mass/weight requirements and inerter force for fixed performance and inertance. It further reduces TMDI stroke and achieves increased robustness to TMDI stiffness and damping properties as well as to the assumed inherent structural damping. It is concluded that by leveraging inertance and top-story stiffness, the proposed solution can efficiently control VS-induced floor acceleration with small additional gravitational (added weight) and horizontal (inerter and damping) forces.