Sliding-mode-based semi-active control for oscillations of structures

Magnetorheological (MR) dampers are semi-active control devices in which the damping forces are controlled by magnetic field. These dampers are well suited for semi-active control of seismically loaded civil structures. In this study, the performance of a semi-active control system based on MR fluid damper is studied. A nonlinear hysteretic biviscous model is used to investigate the MR damper's behavior. The comparison between the analytical and experimental results verifies the theoretical analysis of the developed MR damper. On the other hand, this study focuses on the implementation of MR dampers in a semi-active control system. The algorithms of semi-active control for applications to seismically excited induced structure are studied. The control methods are based on the theory of variable structure system (VSS) or sliding mode control (SMC). A kind of controller is proposed based on the reaching law method. Excellent results are obtained when this strategy is applied to control a model of a seismically excited three-story scaled building. Furthermore, the SMC controller performed better than both the passive-off and the passive-on control systems for its ability to vary its properties to more effectively control the structure. The results clearly demonstrate that the MR damper has the potential for improving the seismic behavior of civil structures.