Structural Protection and Resonance Disruption using the Variable Inertia Rotational Mechanism

Mitigating structural damage and other losses from earthquakes and extreme winds is an ongoing challenge for civil infrastructure. Various passive control strategies and supplemental devices have been developed to control structural vibration. Building off the work on traditional passive control devices, such as tuned mass dampers, viscous dampers and base isolation systems, recent research has focused on the potential of rotational inertial mechanisms. Linear rotational inertial mechanisms, otherwise known as inerters, can transfer translational motion to the rotational motion of a flywheel, consequently creating significant mass amplification effects in the host structure.  While inerters can modify a structure’s dynamic properties, the modifications these linear devices provide are constant, and resonant conditions still exist. As research advances in this area, investigations have been carried out on nonlinear rotational inertial mechanisms and how the variable inertia these devices produce could prove advantageous for resonance avoidance. This thesis focuses on a nonlinear rotational inertia mechanism known as the variable inertial rotational mechanism (VIRM), in which masses can radially move inside the device’s flywheel, continuously changing the moment of inertia of the flywheel and the mass effects the device provides during the response of the structure. This thesis explores the effect of VIRM parameters on the natural frequencies and structural response of single-degree and multi-degree-of-freedom structures, considering different load types and amplitudes. Furthermore, a small-scale VIRM prototype is developed, and its individual components are experimentally characterized to understand their behavior and interaction with the attached structure.  Through numerical and experimental investigations, the effectiveness of the VIRMs at mitigating structural response under various excitations is evaluated and compared to a fixed inertia rotational mechanism. The combined numerical and experimental efforts provide valuable insights into the dynamic characteristics of VIRMs, highlighting their potential for adaptive frequency shifting and enhanced vibration control.