This paper presents a new approach, named Virtual Synchronization Method (VSM), for online identification of stiffness and viscous damping in a civil structure while it is subjected to a harmonic ground motion acceleration. It is assumed that displacement and velocity of the structure relative to the ground are measured in real time. They are used to define a virtual system similar to the actual structure. Proper controllers and estimation functions are designed to force the states of this virtual system to follow those of the actual structure.Theoretical results are derived to study on what conditions, after the two systems synchronized, the estimation functions converge to the true stiffness and damping of the actual structure. Provided numerical examples show that VSM is a promising method for online identification of civil structures and should be the subject of further studies. KEYWORDS adaptive system identification, online identification of structures, real-time estimation of damping and stiffness, smart structures, Virtual Synchronization Method 16
This paper presents an active control scheme for structures with unknown parameters subjected to ground acceleration. It is assumed that the mass, stiffness and damping matrices are unknown to the designer, and no measurement of the ground acceleration is available. Instead, the displacement and velocity vectors are accessible for control purposes. Adaptive block backstepping is used to propose a control force vector which makes the response of the structure follow a predefined reference signal as closely as possible. The provided numerical examples in this paper show the admissible performance of the proposed closed-form solution for the control force. The benefits and drawbacks of this approach are discussed as well.
SUMMARYThis paper studies a design problem concerning installation locations for a number of structural magnetorheological (MR) dampers. The mechanical characteristic of each MR damper is functional dependent to an input current, which is regulated by a Fuzzy Logic controller. It is demanded that the chosen arrangement of dampers should change the dynamic response of the structure to meet certain constraints expressed in terms of minimization of an objective function. For this purpose, an improved version of Ant Colony Optimization algorithm is presented. The modified algorithm also utilizes additional heuristic data derivable from a pre-analysis of the structure in the optimization procedure. Further improvements regarding convergence speed of search algorithm are proposed as well, provided numerical examples study the functionality of the algorithm in different cases. With an acceptable probability from a structural designer's point of view, the proposed method finds qualified solutions during a reasonable number of search iterations.
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