Parametric study and robustness evaluation of rotational impact dampers with three identical rotators for impulsive response mitigation

Integrating the merits of rotational nonlinear energy sinks (RNESs) and impact-based dampers, rotational impact dampers (RIDs) boast a simple configuration and rapid energy dissipation capacity. While the feasibility of RIDs was validated through experiments in a previous study, only a few cases were considered and their working mechanism was not well understood. To this end, systematic analyses are conducted, considering the randomness in the initial positions of the RID, to reveal the influences of RID parameters, input energies, and structural properties on the effectiveness of impulsive response mitigation of a two-story primary structure. First, the mathematical model of RIDs is derived for the non-impact and impact states. Subsequently, a numerical model of the RID-structure system is established, which is validated through both ideal and physical experiments. Focusing on RIDs with three identical rotators, the validated numerical model is employed to investigate the effects of RID mass, eccentricity, damping ratio, and coefficient of restitution on the vibration control performance, from which the working mechanism of the RID is revealed. The RID is then compared with two rotational-type mass dampers in terms of their vibration control effectiveness and robustness against changes in input energy and structural frequency. Finally based on the robustness evaluation, the potential application scenario of the RID is summarized. The results show that the effectiveness of the RID, for both oscillating and rotating rotators, relies on the intensity of the impacts. In particular, the rotating RID attracts energy from the structure and the strong impacts timely dissipate the transferred energy, resulting in targeted-energy-transfer-like control mechanism that quickly and constantly reduces the energy in the primary structure. The RID with appropriate parameters exhibits stronger robustness than the other devices considered, and is particularly suitable for vibration control problems characterized by a broad range of vibrational frequencies and constant displacement amplitudes.