مهندسی عمران شریف (Aug 2017)
DETERMINING CHARACTERISTICS OF OPTIMUM TUNED MASS DAMPER WITH COMBINING TRANSIENT AND STEADY STATE RESPONSES IN DAMPED VIBRATIONS
Abstract
This paper deals with studying the specifications of common control system, known as tuned mass damper, i.e., TMD, and evaluating its efficiency for controlling the structural vibrations. For this purpose, a new method is proposed for designing characteristics of tuned mass damper, i.e. TMD. Here, the effects of both the transient and steady state responses of dynamic system are utilized here for determining the specifications of tuned mass damper, i.e. mass, stiffness, and damping factors. The proposed formulation is presented for structures with natural damping. In other words, the tuned mass damper is designed for damped vibrations. This procedure utilizes a new approach in which the mean of absolute values of the lateral structural displacement ratio is minimized. For this purpose, the Newmark time integration is modified so that it is used for minimizing the mean of absolute values of the structural lateral displacement ratio. It should be noted that the minimization process could not be performed analytically. Therefore, a numerical technique, i.e., the modified Newmark time integration, is utilized here to minimize the mean of absolute values of the lateral structural displacement ratio. This procedure leads to new quantities for mass ratio and TMD's frequency, which are obtained numerically. Afterwards, the proposed technique for designing the tuned mass damper is evaluated analytically and numerically. The analytical evaluation of the suggested technique shows that the proposed design method has more efficiency in comparison with other well-known existing approaches, especially for the common mass ratios. In other words, the developed procedure for determining the characteristics of the tuned mass damper has suitable efficiency to use as passive control mechanism. From this point of view, the suggested method has excellent performance in the resonance condition. Moreover, numerical results show that the developed technique reduces the structural vibrations more effectively in comparison with other design schemes.
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