Research developments in vibration control of structures using passive tuned mass dampers

Vibration Control Identification of Seismically Excited m.d.o.f. Structure-Ptmd Systems

This paper presents a two-stage optimum design procedure for passive tuned mass dampers (PTMDs) to reduce structural dynamic responses with the limitation of PTMD stroke. A new performance index, with the linear combination of structural response ratio and PTMD stroke ratio by a weighting factor α, is proposed. α ranges from 0 to 1.0. The larger the α, the more important the consideration of the stroke. When α equals 1.0, the PTMD is locked. The analytical results show that with little sacrifice of structural control effectiveness, the PTMD stroke can be significantly suppressed when an appropriate α is selected. The numerical simulation of a three-story building under earthquake excitations demonstrated that the proposed optimum PTMD performs as well as the conventional PTMD and its stroke is 30% reduced. Based on the analysis results, it is proved that the new optimum design concept is more flexible and useful in practical application. Copyright © 2009 John Wiley & Sons, Ltd.

Two‐stage optimum design of tuned mass dampers with consideration of stroke

Vibration has long been recognized as a possible source of injury to the human body. Vibration-induced white finger was first recognized in the limestone quarries of Bedford, Indiana as early as 1890-1900 (Taylor et al.1; Taylor2) and was subsequently reported in Italy in 1911 (Griffin3). Since then pneumatic drills have replaced the hammers and chisels used in mining operations. Between the two World Wars, electrically driven grinders replaced hand grinding and in the 1950s, chain saws powered by internal combustion engines replaced hand saws and axes in forestry. Such technical advances led to an increase in hand-arm vibration injuries world-wide where such tools were used. Various epidemiological studies among miners and stoneworkers have confirmed this trend. Such studies were conducted in many countries, including the United States of America (Taylor et al.1; Wasserman et al.4), Canada (Narini et al.5), Britain (Rodgers et al.6), Sweden (Hedlund7), Italy (Bovenzi et al.8; Bovenzi et al.9), Korea (Moon et al.10) and Japan (Matsumoto11; Sakakibara et al.12). Some of these studies reported an extremely high prevalence of vibration-induced white finger among the operators (Griffin13). A recent South African study (Van Niekerk et al.14) confirmed that the levels of vibration on rock drills are high enough to cause an enhanced level of risk of vibrationinduced disorders in a significant proportion of operators. Despite a trend towards mounted drilling there are still many applications where hand held drilling is appropriate. With 60 000 of these drills presently in operation in South African mines, there is a need for rock drill handles that can considerably reduce the levels of vibration to which rock drill operators are exposed. Conventional approaches to reducing the vibration levels at the handle of a tool, such as the use of vibration isolators, result in handles with a high mass and low stiffness that hamper the handling of the drill. Therefore an alternative approach is required. In the present study, the concept of using a tuned vibration absorber was explored and the feasibility of such a solution is demonstrated.

Development of a vibration-absorbing handle for rock drills

Design of Multi-Degree-of-Freedom Tuned-Mass Dampers Based on Eigenvalue Perturbation

Explicit forms of the modal parameters and the envelope of the Green's function for transient response of main structures equipped with vibration absorbers are derived using a perturbation technique and assuming that the natural frequency of the absorber is slightly detuned from that of the main structure Applying these perturbation solutions, the influence of the absorber parameters on the dynamic response of main structures is investigated and the ratio of the envelope for the main mass with absorber to that without absorber is constructed to provide insight to evaluate the effectiveness of the absorber to diminish the vibrations of main structures

H.C. Tsai

Papers

Envelope of green's function for structural response with slightly detuned vibration absorbers