Seismic performance of supplemental inerter and spring with on-off effects for base-isolated structures

The present study investigates the performance of supplemental inerter and spring with on-off effects (ISWOE) in the mitigation of the seismic response of base-isolated structures. Firstly, the response of the rigid base-isolated structure with ISWOE is investigated to see the response control effects of ISWOE under stationary earthquake excitation. The performance of ISWOE in the response reduction of the isolated structure is compared with the corresponding passive inerter and spring. The equivalent damping that was added to the base-isolated structures by the ISWOE was used to measure its performance in mitigating the seismic response. The equivalent damping of the ISWOE is obtained for different values of the isolation period and damping ratio. Subsequently, equations for the equivalent damping of the ISWOE and displacement responses are proposed, and it is observed that they match well with the obtained numerical results. Secondly, using the non-linear model of the ISWOE, the seismic response of flexible base-isolated structures is determined for actual earthquakes, considering different values of the isolation period and ISWOE parameters. The trends of the results of isolated structures with ISWOE under the actual earthquake motions were in good agreement with those under stochastic excitation. Finally, the seismic response of isolated structures with ISWOE by non-linear analysis is compared with the corresponding linear analysis with equivalent parameters of the ISWOE. The isolator displacement of the structures with the ISWOE by the non-linear analysis was observed to match those achieved using the equivalent parameters and by the linear analysis. © 2023 The Author(s)