Incremental Dynamic Analysis Results

Damage to structures caused by earthquakes results in direct and indirect losses that inhibit a community’s ability to recover. The installation of passive control devices is one means to mitigate damage. A variety of passive control devices exist. Inerter-based devices have received attention for their ability to provide large-added mass effects, while having a relatively small physical mass. This is typically achieved with a mechanism that converts translational motion to the rotation of a flywheel. In a clutch inerter, the conversion occurs in a one-way fashion such that energy transferred to the flywheel cannot transfer back from the device to the structure it is attached to. Such behavior could be particularly advantageous in mitigating the effects of near-field earthquakes. However, few studies have considered the seismic performance of structures with clutch inerters. As a result, the effect of the device parameters (i.e., effective mass and damping), the ability of the device to delay the yielding of the structure, and the relative effectiveness of the device in far-field and near-field earthquakes, which more often include a dominant pulse, are uncertain. This paper addresses these gaps in knowledge through a numerical study of a SDOF structure with a clutch inerter. This system, which is modeled in the OpenSees framework, considers the nonlinear behavior of the structure itself that would result from yielding in the structural system in addition to the nonlinear behavior of the clutch inerter. Incremental dynamic analyses were performed with suites of recorded earthquake ground motions. The results of these analyses showed that the clutch inerter is typically significantly more effective than a comparable viscous damper. It was also found that the performance of the clutch inerter was more sensitive to damping when subjected to far-field excitations. The results of this study show that the clutch inerter has great potential as a passive control device for delaying the onset of yielding and otherwise mitigating the effects of a wide range of types of seismic excitations.