Theory And Experiment On Semi-active Control Of Seismic Responses Of Adjacent Buildings Using MR Dampers

Magnetorheological (MR) fluid damper is one of the new semi-active control devices. It has great features of mechanical simplicity, rapid response, and adjustable damping force capacity. The semi-active control system can effectively control the seismic responses of structures based on MR dampers. In this dissertation, semi-active control of seismic responses of adjacent buildings using MR dampers is investigated through theoretical and experimental study, the main work and achievement are as follows:(1) The dynamic performance test of MR damper with different applied current levels is conducted under sinusoidal excitations with different frequencies and amplitudes. A modified Sigmoid model, which has simple expression, clear meaning, and less parameters, is proposed. The parameters in this model can be modified according to the performance test results.(2) Based on the characteristics of Kalman filter, the acceleration feedback control method is introduced to Instantaneous Optimal Control algorithm, Classical Optimal Control algorithm and Linear Quadratic Regulator Optimal Control algorithm. The numerical analysis results indicate that the acceleration feedback based control algorithms can obtain similar control effects as full state feedback control algorithms, which results in fewer sensors needed in the control system and more suitable for engineering application.(3) After investigating the relationship between the control effectiveness and the amplitude of the control force, it is suggested that the optimized control force amplitude should be designed for the MR damper used in a particular control system. The simulation results indicate that the control effectiveness improves slowly with the increasing of the control force when it reaches a certain value. And because the control force amplitude is the basis for designing and manufacturing of MR damper, so the volume and weight of manufactured MR damper based on the optimized control force amplitude can be reduced and less MR fluid is required in the device. Therefore, it would be more convenient for installing and debugging the MR damper in practical engineering application.(4) The application of MR damper in the adjacent structures is studied. Adjacent structures employed with semi-active control algorithm, switch control algorithm, and two passive control algorithms are simulated. The numerical results show that the semi-active control method can obtain the best control effectiveness within four control algorithms. The results further prove that the semi-active control algorithm takes into account the continuous adjustability characteristic of the MR damper, and thus it can make full use of the control devices and obtains great performance on the control of adjacent structure.(5) A series of shaking table tests of the adjacent model structures installed with MR damper were carried out under different seismic excitations. Two passive cases and three acceleration feedback based control cases are considered. The experimental results show that the semi-active control systems can reduce the structural responses significantly. And the acceleration feedback based control algorithms can greatly reduce the number of sensors required in the control system, which makes it more convenience for applying the control algorithms in engineering application.