The yield stress, and visco-elastic properties of ER materials increase by an order of magnitude when the material is subjected to strong electrical fields (kV/mm). Because the electric field controls the yielding behavior of ER materials, ER devices are inherently non-linear. ER materials may be incorporated very simply within a viscous damping wall. This configuration for an ER device is attractive because ER damping walls do not require seals, hoses, or any moving parts. These walls can provide large forces by virtue of the large area of the wall. In this study, a dynamic numerical model for the damping wall is used in parallel with a base-isolation system to protect a ductile three story hospital building. A Lyapunov-based controller is designed to to suppress seismically-induced structural motions with respect to an inertial frame of reference. The control decisions are independent of the structural model, and are therefore robust to modeling errors. Structures operated according to the control rule maintain an anti-resonant condition. This is demonstrated in the time-domain and the frequency domain.
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