Dynamics: Vibration Reduction

A tuned mass damper (TMD)

This demonstration compares free vibrations of a SDOF system and a similar system with a tuned mass damper, and shows the effect of the tuned mass damper in free vibration.

Fig. 18-5: Comparison of vibration with and without a tuned mass damper

Fig. 18-5 shows a single degree of freedom (SDOF) system consisting of a mass and a spring attached to the left hand of a cross arm. The same SDOF system is attached to the right end of the cross arm and a smaller SDOF system has suspended from it. The smaller SDOF system, which is used as a tuned mass damper, has the same natural frequency as that of the main SDOF system. In other words, the ratio of stiffnesses of the two springs is the same as the ratio of the two masses.

Displace the two main SDOF systems downward vertically by the same amount and then release them simultaneously. It can be seen that the amplitude of vibration of the SDOF system on the left is greater than that of the one on the right. The tuned mass damper vibrates more than the mass to which it is attached. The vibration of the tuned mass damper applies a harmonic force to the SDOF system, which suppresses the movements of the main mass.

The effect of a tuned mass damper is most significant if a harmonic load is applied to the system with a frequency close to the natural frequency of the system.

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