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A tuned-mass damper (TMD), also known as a pendulum damper, is not really a damper, but rather a pendulum or another gravity-based oscillator which is attached to the structure in such a way that it counteracts the vibration of one or more fundamental modes, thereby reducing the wind and/or seismic response of those modes.
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- Model 2 – TestModel_With TMD.SDB features a subsystem which simulates the effect of a pendulum damper.
Figure 1 - Model 2 - Test model with TMD
Procedure
The general procedure for modeling a tuned-mass damper is given as follows:
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- Mass – Mass strongly affects how the TMD influences response. Changes to mass must be accounted for in the following locations:
- Mass (M) should be assigned to the free joint (J-end of the link).
- Weight (W = Mg) should be assigned to the free joint (J-end of the link) as a joint force load in the gravity direction in any self-weight load pattern.
- Effective stiffness (Mg/L) of the U2 and U3 link properties.
- Period – Generally, the period (T) of the TMD is chosen to closely match the structural period to be counteracted, taken as the first period of vibration of control model. Note that, although the mass does not affect the period of the TMD, it does affect how strongly the TMD affects the rest of the structure, with larger masses typically having a larger effect. The period of the TMD is given by:
Once the period of the TMD is derived, TMD length is calculated from this value and gravity. This length, along with gravity and the arbitrary mass value, are then converted into the effective link stiffness of the U2 and U3 directions, given as Mg/L. This being the case, the length of the TMD in the real structure is not explicitly modeled, but is accounted for in the link property.
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