Magneto-rheological elastomers (MREs) are a class of smart materials which can adjust their modulus or stiffness by an applied magnetic field. Thus, MREs can be used as controllable stiffness elements in various engineering systems. In order to use them for engineering applications, characterizations of MRE behaviors under magnetic fields and developments of dynamic models (such as a phenomenological model) that can capture the behaviors must be studied well. This paper focuses on modeling of MRE samples under shear deformation, which is a common mode of operation of MRE materials in structural engineering. It proposes a dynamic model that combines the Ramberg-Osgood model and the Maxwell model. The model is validated using experimental characterization test data. The results show that the proposed dynamic model can be effectively used for predicting the dynamic behavior of MREs under shear deformation.

This study experimentally evaluates the seismic performance of a newly proposed smart base-isolation system. The proposed system employs magneto-rheological (MR) elastomers whose modulus or stiffness can be changed by the magnitude of an applied magnetic field. Hence, as controllable stiffness elements, MR elastomers are capable of improving seismic protection of base-isolated structures. In this study, a small-scale MR elastomer-based base isolation system is designed and fabricated. Installed in a single-story shear building structure, the dynamic characteristics and responses of the smart base-isolated structure under harmonic loadings are examined. The test results show that the smart base-isolation system outperforms an equivalent conventional passive-type base isolation system in reducing the responses of the scaled building structure.

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.