Title: Semi-Active Control of Nonlinear Structures
Abstract: Since semi-active control systems offer advantages of both passive and active control systems and mesh well with the requirements and constraints of seismic applications such as very low energy requirement, therefore they have attracted extensive attention in structural control researches and applications. Also magnetorheological (MR) damper as a promising semi-active control mechanism for seismic response reduction has been used extensively in recent years. On the other hand, in most of the previous researches on the application of semi-active systems the main focus has been on developing algorithms and assessment of the efficiency of control mechanisms in reducing the seismic response of linear structures and the researches dealing with nonlinear structures have been limited. Since under strong earthquakes structural members might experience yielding, hence in this paper the application of MR damper for mitigating the response of seismically excited nonlinear hysteretic structures has been studied. Because of the inherent non-linear nature of MR damper and also non-linear behavior of structure, one challenge to effectively utilize MR damper is developing an appropriate semi-active control algorithm. In this research the clipped-optimal control algorithm has been extended to be used for semi-active controlling of non-linear frames equipped with MR damper. Bouc-Wen model has been used for defining the dynamic behavior of MR damper. Accelerations of stories that are readily measurable were used for feedback and acceleration feedback control strategies based on methods were advocated for determining desired optimal control force. To demonstrate the effectiveness of the proposed approach and employing MR damper for reducing the response of non-linear structures, 3 and 5 story shear frames with bilinear hysteretic behavior subjected to different earthquakes and the capability of MR damper in mitigating the structural response has been studied. Sensitivity analysis on different parameters of control algorithm and MR mechanism has been performed. Also to assess the effect of earthquake characteristics on the performance of MR damper on nonlinear frames, the results of numerical analysis under both near-filed and far-field excitations has been reported. The results of numerical simulations show the effectiveness of the proposed method as well as MR damper in improving the seismic behavior of nonlinear frames.
Publication Year: 2010
Publication Date: 2010-01-01
Language: en
Type: dissertation
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