Tuned mass damper
As a vibration damper ( TMD or even short Tilgerpendel ) are referred to special types of vibration dampers. Mass dampers are not fixed between two objects, but only one. The natural frequency of the damper is tuned to the resonant frequency of the object to be eliminated. At this frequency, the object performs only small movements. Below and above this frequency, the amplitude of the object, however, is greater than without absorber.
Principle of operation
The damping mass forms, together with a separate damping spring is a pendulum whose natural frequency is adjusted to the resonant frequency to be eliminated (for example, the building). At this frequency, the damper can perform large excursions - the forces on the spring starting point ( = the reassuring structure to the attachment point) are therefore also large. The vibration escapes at this frequency the structure vibration energy for its own vibratory movements.
Work entirely analogous for the special case of torsional vibrations dual mass flywheels.
By coupling the two oscillatory structures can arise and above and below the absorber natural frequency new natural frequencies, resulting from the combination of the structure with the damper. At these two frequencies is obtained for the structure inherently a deterioration of the situation ( more vibration).
In a few simple cases, TMD can be dimensioned by means of simple rollover formulas. However, once the excitation is not a single frequency, but broadband and not harmonious, but transient occurs, more detailed studies are required to determine the optimum damping. This is often adaptive, that is, it can automatically adjust itself to the conditions.
In addition, there are active hydraulic systems Tilgerpendeln which are capable of bringing the vibration of the building to zero.
A distinction must be:
- Ordinary (passive ) vibration absorber,
- Actively controlled damper and
- Semi-active mass dampers, in which the energy required in the necessary, is typically stored in the form of a preloaded spring ( locking and release only above a certain threshold value )
Applications
Structures
Tilgerpendel serve to absorb the building vibrations generated in particular by wind, but also by earthquakes and human influences. Classical applications are, for example, pedestrian bridges, bridge pylons, steel chimneys or long-span (steel ) Stairs or machines for noise reduction.
Buildings located in the catchment area of industry shocks or in earthquake zones are equipped in this way. Best known are the Tilgerpendel used in tall buildings, which prevent swaying caused by wind vibration in buildings. Reason for its use is not only the building security, but also the comfort.
Examples of structures with vibration absorbers:
- Akashi - Kaikyo Bridge, Japan, damper in the bridge pylons
- Berlin TV Tower, Berlin, in the spire suspended 1.5t Tilgerpendel
- Burj al Arab, Dubai, 11 vibration damper in building
- Comcast Center, Philadelphia, the world's largest water-filled damper (1300 tonnes in weight, over 1200 cubic meters of water )
- Millennium Bridge, London, vibration damper 58 in the bridge structure
- Taipei 101, Taipei, 660 t- Tilgerpendel against wind; two 4.5 ton Tilgerpendel against fatigue design
- Masts of DHO38, vibration absorber against wind-induced vibrations, granulate filled cylindrical thickening
Overhead lines
An electric overhead lines Stockbridge vibration damper are used to dampen vibrations, which are excited by the wind.
Combustion engines
The excited gas and inertial forces in the crankshaft vibration is reduced by the use of a crankshaft damper.