| In the area of vibration control, the method of semi-active control in the vibration of the structure has been more concerned because of its advantages that less input energy, better effect of control and more practical. Using negative stiffness vibration control based on the Magnetorheological dampers is a better way of semi-active control. According to the adjust the exciting current of the magnetic core, the hysteresis loop from the Magnetorheological dampers can be negative stiffness that can be equaled to the sum of ordinary damping forces and negative stiffness controlling force in analysis. In this research, according to the analysis, the accelerated speed and displacement of the structure have been better controlled since the negative stiffness controlling force and damping force working at the same time. Those outcomes initially proved the damping advantage of the negative stiffness magnetorheological dampers. For the negative stiffness magnetorheological dampers, this dissertation mainly focuses on the following aspects:1) Multi-degrees of freedom of the structure of the negative stiffness damper vibration problem has been studied. The researcher did the modal analysis and numerical stimulation to the negative stiffness damping in a double degree of freedom system, and had a study of positive and negative stiffness dampers optimized arrangement to ten layers of the simplified model and the20-stories steel structure Benchmark model by genetic algorithm. As a result of that, an arrange rule of different stiffness damper damping in a multilayer structure had been found, which is that the positive stiffness damper should be placed on the first floor of the structure, the negative stiffness damper should be placed in the lower and middle part of a structure, moreover, the positive stiffness damper should be placed in the upper part of the structure, the degree of stiffness of two adjacent damper should be changed gradually. Meanwhile, the optimized process also proved that in a multilayer structure, rationally use negative stiffness dampers could achieve a better effect of vibration control than using the traditional viscous dampers. This research used a new method that mixed MATLAB and SAP2000during the optimized analysis of Benchmark structure, which proved a more convenient way to intelligent structure analysis.2) Negative stiffness of magnetorheological damper is developed and its control system. Based on the need of negative stiffness control and the experiment, two magnetorheological dampers have been developed. Also regarding DSP as the core of calculating control, we developed a negative stiffness controller of negative stiffness dampers and an adjustable constant current source. The performance-testing outcome demonstrated that the output ranges of these two magnetorheological dampers are80N to1400N and80N to1200N. Furthermore, the dampers had a full hysteresis loop under a constant excitation current. When the damper working with the negative stiffness controller and other relevant equipment, different negative stiffness status hysteresis loop can be generated by different controlling parameters.3) The negative stiffness of magnetorheological damper vibration table experiment has been done. A negative stiffness damping experiment of a four-layer steel frame had been taken on the upgraded vibrating table, and the result of the experiment is basically the same as the analysis. Consequently, the negative stiffness damper has a better controlling effect to accelerated speed than ordinary viscous dampers and damper positive stiffness, meanwhile it can also reduce the peak value of interlaminar displacement among the whole structure.In conclusion:The negative stiffness damper and its controlling system that presented by this dissertation is a good structural vibration-damping device. At the same time of reducing lateral stiffness of the structure, and improving damping ratio, it can also reduce the peak value of interlaminar displacement. This would show a good application prospect. |
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