Types and Features of Vibration Damping (Seismic) Devices
(1) Vibration (vibration) damper (vibration control component)
Figure 1 Mechanism of Vibration Damping (Seismic) Damper
Bracing materials incorporating oil dampers, etc., are installed on walls and other surfaces to absorb the shaking of the shaft assembly by the damping force of the damper. Since the damper must expand and contract to some extent to transmit damping force, a vibration control damper installed in a building, as shown in the figure below, is effective during large shaking to some extent (e.g., during an earthquake). On the other hand, it is not so effective in the case of slight shaking.
Figure 2 Vibration control (seismic) damper
②TMD（Tuned Mass Damper）
Figure 3: How TMD works
When a spring-supported weight is attached to an object whose vibration is to be suppressed and moves at the same period, the weight reacts and moves well, absorbing the shaking of the object. The TMD is a vibration control device that utilizes this principle.
The characteristic of TMD is, as the name implies, tuning (entrainment). It is good if the tuning is correct, but if it is out of tune, the effect will not be apparent. Also, if the target has multiple modes (two or more oscillation-prone cycles exist), the effect is obtained only for the cycle in which the TMD is tuned.
*Two types of TMDs are required to produce an effect for two modes. The larger the mass of the weight, the higher the effect, but it is necessary to determine the appropriate amount through preliminary analysis, as a large TMD cannot be unnecessarily attached.
The photo below shows a TMD (about 1 ton of weight) to reduce vertical sway when walking on a floor or bridge structure. It is usually installed on the beam behind the floor like this.
Figure 4 TMD
③AMD（Active Mass Damper）
Figure 5: How AMD works
It is the same as TMD in that the vibration is reduced by the reaction force of the weight. Since an actuator (motor or other driving device) is attached and the weight can be moved as large as desired, it is possible to efficiently reduce the vibration of the object by controlling it well.
A much smaller weight than a TMD produces a greater effect and does not require tuning to the object. In addition, a single unit can be effective for multiple modes and can follow changes in the object over time (e.g., changes in natural frequency). Yacmo is a group of active vibration control professionals! Yacmo has a proven track record in AMD and other active vibration control technologies, and can provide advanced vibration control.
The photo shows AMD for vertical floor vibration (vertical vibration). Left: movable mass 600 kg type, right: 50 kg type, which can be seen in the hands-on showroom. Click here for showroom details
Figure 6 AMD
Vibration Damping (Seismic) Devices Matrix
We have tried to express the target sway in a matrix that divides the sway as large/small sway x vertical/horizontal sway, and considered what range the vibration control devices (1) to (3) introduced above can cover.
AMD and TMD are vibration control devices that can handle both vertical (vertical vibration) and horizontal (horizontal vibration) vibrations, from minute environmental vibrations to major aftershocks such as those caused by earthquakes.
Vibration Damping (Seismic) Devices Matrix