Tuned Mass Dampers
The make-up of a tuned mass damper consists of an inertia element (a mass) and a suspension mechanism comprised of restoring and dissipative elements. The most commonly used suspension mechanism in TMDs is the parallel combination of coil springs and viscous dampers, but they can also be realized using other suspension mechanisms such as air, viscoelastic and pendulum. TMDs are variations of the more general tuned absorber/dampers commonly used in treating narrow-band noise and vibration issues.
The schematic of a tuned mass damper (the red, 2nd order systems M2-K2-C2) appended to a vibrating structure (resembled by the black, 2nd order system M1-K1-C1) is shown in Figure 1.
Tuned dampers are sized so that a) their inertia/mass is large enough to ensure their effectiveness, b) their resilience in conjunction with their inertia/mass realizes the desired tuning frequency, and c) enough energy dissipation capability is built into them so that they effectively damp the vibration of their target modes.
TMDs are tuned by setting their natural frequencies substantially equal to the resonant frequencies of the structure targeted for damping.
Figure 1 The schematic of a tuned mass damper installed on a structure
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 (no need to be anchored at the other end) and could be placed within the structure.