Mechanical resonance#Resonance disaster

The resonance catastrophe called in mechanics and construction, the destruction of a building or a technical device by excessive Schwingungungsamplituden at resonance. In a periodically recurrent excitation whose frequency corresponds to a resonant frequency, more energy is transferred to the system and is stored there. The vibration energy is dissipated by damping effects is always present in part of the system. If the energy input exceeds the power loss, the oscillation amplitude is always larger until the load limit is exceeded.

Causes

The excitation of the resonant oscillations may be carried out with a predetermined frequency from the outside, which matches a resonance frequency of the vibrating structure.

Protection measures

To protect the structure vibration absorber be installed to dampen strong in the area of the resonance frequency and thus dissipate the energy input (such as the tallest building in 2005, the Taipei 101, a massive Tilgerpendel over several floors ). Furthermore, the construction is designed for a natural frequency, which typically does not occur in the operation. In seismic zones one is guided by the locally typical vibrational frequencies of the ground shaking.

On overhead lines resonance effects can lead to the destruction of the insulators and electrical shorts. As a remedy, Stockbridge vibration damper used on the conductor cables.

Examples of resonance disasters

The following cases are known examples of excessive sympathetic vibrations that have led to the destruction:

• On April 12, 1831 74 British soldiers were marching on the Broughton Suspension Bridge. The bridge collapsed due to vibration; 40 soldiers died in the Irwell, 20 of them were injured, six seriously. To prevent this danger, it is often forbidden and Germany according to § 27 (6 ) Highway Code forbidden to march in lockstep across a bridge.
• When " Zersingen " a glass of the self-oscillation is by sonication at its natural frequency so strongly excited, that it shatters. This is for example possible with a tone generator. The human voice is not generally appropriate to bring a glass to overflowing, as neither the necessary sound pressure, nor the purity of the frequency can be achieved. In an episode of Mythbusters, the singer Jaime Vendera brings a wine glass using only his voice to resonate disaster.
• On April 16, 1850 485 ​​French soldiers marched across the swinging suspension bridge in the storm of Angers. While the soldiers marched without impact, but reinforced the vibration through the motions, with which they sought the balance in the same cycle; the two supporting ropes torn, collapsed the bridge; 226 soldiers were killed.