TUNED MASS DAMPERS (TMDs)
Tuned mass dampers are used for adding tuned damping to various structures, quieting their resonant vibration.
Tuned mass damper (TMD) is a vibrating mass that moves out of phase with the perturbing force inducing vibration in the structure the TMD is installed on. With its out of phase motion, the inertial force of the TMD mass abates the resonant vibration of the structure by dissipating its energy. The ideal extent of phase difference between the motion of the TMD mass and that of the structure, i.e., 90 degrees, is attained by tuning the TMD to the natural frequency of the structural mode targeted for damping.
Considering that the first vibration mode of a structure plays a dominant role in its dynamic response, a TMD is normally (but not always) tuned to the first natural frequency of the structure. The energy dissipation effectiveness of a TMD depends on a) the accuracy of its tuning, b) the size of its mass compared to the modal mass of its target mode, i.e., its mass ratio, and c) the extent of internal damping built into the tuned mass damper.
DEICON designs, fabricates, and implements passive, semi-active, and active tuned mass dampers for a variety of structures including floor systems, balconies and mezzanines, monumental staircases, pedestrian bridges, observation towers, and piping systems. Depending on the application, DEICON TMDs are configured with different suspension mechanisms including viscously damped coil springs and/or air springs, viscously damped pendulum, as well as viscoelastic.
Contrary to broadband (viscous, viscoelastic, and friction) dampers which need to be attached to the vibrating structure at one end and anchored to a massive support at the other, tuned mass dampers need to be connected to the vibrating structure at one end only (they do not need to be anchored at their other end).
For structures that can neither support the weight nor accommodate optimally sized TMDs, DEICON proposes the use of active tuned mass dampers (ATMDs) and active mass dampers (AMDs) which can provide as much effectiveness as passive TMDs twice as massive and large.