The Clutching Inerter Damper in Base Isolation and with Variable Inertia for Vibration Control

Base isolation systems (BISs) are used to isolate equipment or structures from vibration sources; however, the reduction in transmitted loads with the BIS can come at the cost of large isolation layer displacements. The clutching inerter damper (CID) is a device that combines flywheels that have clutching mechanisms with a mechanism that converts translational motion into rotational motion. The CID is proposed to be coupled with the BIS to improve its isolation performance and simultaneously decrease the associated isolation layer displacements. The CID acts as a linear inerter when in its engaged state, adding effective mass in the form of rotational inertance to oppose a system’s motion, and, when disengaged, it idles freely and dissipates its rotational energy without directing this energy back into the system. Previous studies on the CID in base-isolated multi-degree-of-freedom (MDOF) structures are limited in focus, and much of the research on this topic considers an ideal CID where all rotation is damped out between engagements, which is often not physically realistic. This work numerically investigates the performance of a base-isolated MDOF system with a CID subjected to white noise loading from a frequency domain perspective and employs a more realistic numerical model of the CID’s dynamics. Several indices, such as the H2 analog of displacement and acceleration frequency response functions, are analyzed to evaluate the system response. Results indicate that the BIS with a CID outperforms other similar configurations for several key indices, illustrating its effectiveness in isolation systems. The analysis also reveals that increases in the CID’s ability to improve system performance slow with higher levels of rotational inertance. Additionally, the discontinuous behavior of the CID's mass effect creates undesirable high frequency noise upon engagement with the structure. A secondary investigation numerically evaluates the CID with variable inertia (CIDVI) which can engage with a host structure at a low level of inertance, reducing the dynamic impact to the structure, whereafter the inertance can increase with flywheel velocity due to centrifugal forces. The CIDVI's performance is assessed with the H2 analog of system absolute acceleration, RMS force transfer, and system maximum absolute acceleration, revealing the performance of the CIDVI is highly amplitude dependent but offers effective acceleration and displacement control as well as energy dissipation.