Investigation of the Impact of Slider Mass Stiffness on the Behavior of the Variable Inertia Rotational Mechanism for Structural Vibration Mitigation

Structural control devices can help mitigate the response and subsequent damage to structures that result from dynamic loads, such as earthquakes and wind loads. Rotational inertial mechanisms offer a promising avenue for achieving this goal by providing significant mass effects without the need for large physical masses. Among these mechanisms, the variable inertia rotational mechanism (VIRM) is a nonlinear control device with adjustable rotational inertia and thus produces modifiable mass effects, achieved by incorporating slider masses inside the device’s flywheel. While previous research on the VIRM has predominantly focused on active or semi-active control systems, the passive implementation of VIRM and its efficacy in vibration mitigation remains relatively unexplored. As a result, the effects of the device parameters, most prominently slider stiffness, and the impact of these parameters on the device’s ability to reduce response under random excitation are uncertain. This chapter addresses these gaps in knowledge through a numerical study considering a single-degree-of-freedom primary structure. The study aims to investigate the different stiffness characteristics of the VIRM, including modeled properties of the stiffness element attached to the slider masses, on the natural frequency shifts and response mitigation. The natural frequency and response measures are evaluated by estimating the system’s instantaneous frequency and an H₂-based measure. The results of this study highlight the ability of VIRM to shift natural frequencies and reduce response in structures subjected to random excitation and will encourage the further study of these innovative devices.