Effects of near-fault and far-fault ground motions on seismic responses of multi-storey building structures controlled by tuned mass damper inerter

The tuned mass-damper-inerter (TMDI) is a newly developed passive energy dissipation unit that combines the conventional tuned mass-damper (TMD) with an inerter mechanism to attenuate undesirable vibrations. Far- and near-fault earthquake characteristics influence optimal TMDI parameters in controlling displacement demands on building structures. This study provides a comprehensive evaluation of the impact of TMDI on the structural response of linear-behaving multi-degree-of-freedom (MDOF) structures subjected to far-and near-fault earthquake-induced ground shaking. The chosen near-fault records guarantee motions with forward directivity (FD) and motions with fling step (FS). An approach based on a genetic algorithm (GA) is used to tackle the optimization problem. The objective function that needs to be minimized is the displacement of the building's top story. On the basis of predetermined mass and inertance ratios, the single-objective minimization method is used to compute the optimal design parameters (damping and frequency ratios). TMD and TMDI's optimal control capabilities are compared, and an inerter dependence analysis is conducted to probe the effect of the improvement. It is analytically demonstrated that the TMDI performs better than the conventional TMD for relatively small mass ratios, regardless the distance from a fault rupture. However, the TMD's high-mode dampening effect can be further enhanced by increasing the inertance of the inerter. Additionally, buildings excited by near-fault records with FS have a higher seismic demand on their induced responses. Lastly, the inerter's mass-amplification effect can either enhance the performance of the conventional TMD, for a certain TMD mass, or replace a portion of the TMD's oscillating mass, to realize a substantial weight reduction at a desired level of vibration suppression.