Experimental Study Of Semi-Active Real-Time Cotrol For Seismically Excited Structures

Semi-active seismic control has attracted considerable interests in the area of structural vibration control in recent years. MR damper has been among the most practical semi-active control device since its force output can be readily adjusted by the external control voltage. This paper presented a shake table test for the real-time semi-active seismic control of a lab structure using the MR damper.Firstly, the robustness of some models for MR dampers to the variation of excitation frequencies was evaluated. It is found that Dyke's model is more robust than others but exists a redundant parameter in the Bouc-Wen section, so a normalized parametric model was proposed to eliminate such a redundancy. The parameters in the new model were identified by SQP through the sinusoid excitation test for the damper.The test structure is a 3-story steel frame lab model. Accelerometers were mounted on each floor and the ground level, and MR dampers served as control device. The structural model was identified though processing the measured acceleration signals by ERA. The effect of frequency contents of earthquake on the performance quality was considered in the design of semi-active controller. Based on acceleration feedback of some local floors, the controller can output the 'ideal' control force by LQG algorithm; then adjusting the control voltage to make the damper force trace the 'ideal' control force as closely as possible by Bang-Bang selection algorithm. Based on this control strategy, a discrete controller program for real-time test and an analytical simulation program for the control system were coded, respectively.Three control strategies were experimentally studied for three earthquake excitation levels. A subset of evaluation index was defined for assessing different control strategies. For all the earthquake excitation levels, the experimental results indicated the semi-active control shown the better performance than the other two passive control cases, in which a constant voltage of either 0 or maximum value is applied to MR damper. The experimental results coincided well with the analytical ones. As demonstrated the effectiveness of the proposed semi-active control strategy and verified the analytical computer program as well.