Research On MTMD System For Suppressing Vibration Of Tall Buildings Subjected To Wind Loads

As a kind of special structure, high-rise structures are more often used in many fields, the wind-vibration control is essential to structures, because the natural frequency of high-rise structures closes to wind's predominant frequency.With the development of structural vibration control techniques, many new vibration control methods have been proposed. Among others, MTMD (multiple tuned mass damper) is an effective one. It consists of a group of TMD( tuned mass damper), whose frequencies are required to have a distribution around the natural frequency of a controlled mode of the structure. In this way, a frequency range is formed so that MTMD is able to remedy the disadvantages of TMD, i.e. the sensitivity to a fluctuation in the natural frequency of the structure, and less robustness etc.In the present paper, the fundamental characteristics or performances of MTMD are investigated analytically, and the parameters are optimized including the frequency range of MTMD's, the damping ratio of each TMD and the total number of TMD's. The robustness in comparison with TMD and the applications in civil engineering of MTMD's are also discussed.Firstly, the explicit expression is derived for the dynamic magnification factor of the high-rise structure with MTMD. Physically, this factor is defined as the control effectiveness index for suppressing vibration of the structure subjected to White Noise. The influence of MTMD's parameters upon the dynamic magnification factor was analyzed, and it shows that the frequency range of the MTMD is the most important or primary parameter in its design and the damping ratio and the total number of TMD's are in a sense secondary parameters. By applying the criterion of the minimum values of the maximum dynamic magnification factors, the optimum parameters are obtained. Then they are used to control the response of Luoyang TV tower subjected to wind excitation. Results indicate that using optimum parameters can significantly reduce the displacement and acceleration responses. On the other hand, the robustness of the MTMD against the error in the natural frequency can be improved to a great extent. In order to apply in engineering easily, design steps as well as a table of related optimum parameter is proposed for the considered MTMD. Secondly, quasi-optimization theory is used in studies of the passive control, so several modes of the structure can be taken into account. As an algorithm in quasi-optimization theory, the equivalent optimal control method has been improved for its faultiness in optimizing the parameters of MTMD's. The bi-equivalent optimal control method is proposed. At the end of the paper, a practical application of MTMD structure in civil engineering is discussed and an innovative vibration-control system named Mega-sub structure is presented.