Clutching Inerter Damper for Multidegree-of-Freedom Base-Isolated Structures: A Numerical Study

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 proposed to be coupled with the BIS to improve its isolation performance and simultaneously decrease the associated base 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 and focus heavily on the time history analyses of seismic or harmonic loadings. Furthermore, much of the research on this topic considers an ideal CID where all rotation is damped out between engagements, which is not physically realistic in many circumstances. 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 and H infinity analog of displacement and acceleration frequency response functions, are analyzed to evaluate the system response. The performance of the BIS with the CID is compared against the BIS with a linear inerter, the BIS without a CID or inerter, and the superstructure without base isolation. Results indicate that the BIS with a CID outperforms the other configurations for several key indices. The analysis also reveals that increases in the CID's ability to improve system performance slow with higher levels of rotational inertance. The performance of the CID illustrates its potential effectiveness for isolation systems in MDOF structures.