Adaptive seismic isolation of structures using MR-fluid dampers

This paper presents the modeling and control of an MR damper installed between the ground and first floor of a 5-story base isolated building. The building structural model is derived from a benchmark structure model using ETABS. The MR damper model considered is derived from Bouc-Wen Hysteresis model proposed by Spenser et al [1], and several other authors. System identification technique is used to derive a simple 4^th order nonlinear model that best approximates the dynamics of the actual MR damper. The dynamic behavior of this simple model is tested and validated over a wide range of inputs and proved to be very representative of the Bouc-Wen Hysteresis model. A Kalman filter is designed to best estimate the state of the structure-damper system for the purpose of feedback implementation. An LQG based controller is designed to control the MR damper under dynamic loads. The effectiveness of this control strategy over a wide range of historical earthquakes is demonstrated. Accelerations and drifts at all building floors are computed and plotted. The controlled and uncontrolled results are compared and significant improvement in the MR damper performance is demonstrated.