A tuned mass damper (TMD) is a device consisting of small damped spring–mass system attached to a vibrating main system in order to attenuate any undesirable vibrations. In this paper, optimum parameters of TMD system attached to a viscously damped single degree-of-freedom main system are derived for various combinations of excitation and response parameters. The excitation applied to the main system consists of external force and base acceleration modelled as Gaussian white-noise random process. Using numerical searching technique, the optimum damping and tuning frequency ratio of the TMD are obtained for minimization of various mean square responses such as relative displacement, velocity of main mass and force transmitted to the support. The optimum parameters of the TMD system and the corresponding response quantities are obtained for different damping ratios of the main system and the mass ratios of the TMD system. Explicit formulae for damper damping, tuning frequency and the corresponding minimized response are then derived using curve-fitting technique that can be conveniently used for applications in dynamical systems. The error in these expressions is found to be negligible and hence these expressions are convenient for use in damped single degree-of-freedom main system. The optimum damping ratio of the TMD is not much influenced by the damping of the main system. However, the optimum tuning frequency of TMD is significantly affected by the damping of main system. Lastly, a comparison of the optimum damping and tuning frequency of the TMD under filtered white-noise and white-noise excitation is also made. Copyright © 2006 John Wiley & Sons, Ltd.

An update state-of-the-art review of the behaviour of isolated bridges to seismic excitation is presented. The review includes the literature on theoretical aspects of seismic isolation, parametric behaviour of base-isolated bridges and experimental studies to verify some of the theoretical findings. A brief review of the earlier and current base isolation devices, proposed or implemented, is given, and aspects for future research in the area of isolation of bridges are included.

Analytical seismic responses of structures retrofitted using base isolation devices are investigated and the retrofit schemes are illustrated. The retrofitting of various important structures using seismic isolation technique by incorporation of the layers of isolators at suitable locations is studied. Three specific structures such as historical buildings, bridges, and liquid storage tanks are selected to investigate the effectiveness of the base isolation in seismic retrofitting. Different types of isolation devices, such as elastomeric bearings and sliding systems are evaluated for their performance in the retrofitting works. The response of the retrofitted structural system is obtained numerically by solving the governing equations of motion under different earthquakes and compared with the corresponding conventional structure without any retrofit measures, in order to investigate the effectiveness of base isolation in retrofitting of structures. It is observed that the seismic response of the retrofi...

The effectiveness of tuned mass friction damper (TMFD) in suppressing the dynamic response of the structure is investigated. The TMFD is a damper which consists of a tuned mass damper (TMD) with linear stiffness and pure friction damper and exhibits non-linear behavior. The response of the single-degree-of-freedom (SDOF) structure with TMFD is investigated under harmonic and seismic ground excitations. The governing equations of motion of the system are derived. The response of the system is obtained by solving the equations of motion, numerically using the state-space method. A parametric study is also conducted to investigate the effects of important parameters such as mass ratio, tuning frequency ratio and slip force on the performance of TMFD. The response of system with TMFD is compared with the response of the system without TMFD. It was found that at a given level of excitation, an optimum value of mass ratio, tuning frequency ratio and damper slip force exist at which the peak displacement of primary structure attains its minimum value. It is also observed that, if the slip force of the damper is appropriately selected, the TMFD can be a more effective and potential device to control undesirable response of the system.