This article investigates a smart base-isolation system using magnetorheological (MR) elastomers, which are a new class of smart materials whose elastic modulus or stiffness can be adjusted depending on the magnitude of the applied magnetic field. The primary goals of this study are to develop a smart base-isolation model that represents the field-dependent dynamic behaviors of MR elastomers, to design and construct a scaled smart isolation system and a scaled building structure for a proof of concept study and to investigate the dynamic performance of the smart base-isolation in mitigating excessive vibrations of the scaled building structure under earthquake loadings. To this end, a dynamic model of an MR elastomer was first obtained based on characteristic test results of MR elastomers in shear mode. The dynamic model was then incorporated in a shear building model. Its effectiveness was validated by comparing the test results of a small-scale, single-story building structure coupled with the MR elastomer under harmonic excitations. After validating the MR elastomer-based base-isolation system, a further numerical study was performed to evaluate its effectiveness under seismic excitations. The results show that the proposed MR elastomer base-isolation system with the fuzzy logic control algorithm outperforms the conventional passive-type base isolation system in reducing the responses of the building structure for the seismic excitations considered in this study. The results further suggest that the feasibility of using MR elastomers as variable stiffness elements for enhancing the performance of conventional base-isolation systems.
Recently, magneto-rheological (MR) elastomer-based base isolation systems have been actively studied as alternative smart base isolation systems because MR elastomers are capable of adjusting their modulus or stiffness depending on the magnitude of the applied magnetic field. By taking advantage of the MR elastomers’ stiffness-tuning ability, MR elastomer-based smart base isolation systems strive to alleviate limitations of existing smart base isolation systems as well as passive-type base isolators. Until now, research on MR elastomer-based base isolation systems primarily focused on characterization, design, and numerical evaluations of MR elastomer-based isolators, as well as experimental tests with simple structure models. However, their applicability to large civil structures has not been properly studied yet because it is quite challenging to numerically emulate the complex behavior of MR elastomer-based isolators and to conduct experiments with large-size structures. To address these difficulties, this study employs the real-time hybrid simulation technique, which combines physical testing and computational modeling. The primary goal of the current hybrid simulation study is to evaluate seismic performances of an MR elastomer-based smart base isolation system, particularly its adaptability to distinctly different seismic excitations. In the hybrid simulation, a single-story building structure (non-physical, computational model) is coupled with a physical testing setup for a smart base isolation system with associated components (such as laminated MR elastomers and electromagnets) installed on a shaking table. A series of hybrid simulations is carried out under two seismic excitations having different dominant frequencies. The results show that the proposed smart base isolation system outperforms the passive base isolation system in reducing the responses of the structure for the excitations considered in this study.
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