Resonance disaster

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In terms of mechanics and construction, the resonance catastrophe describes the destruction of a building or a technical facility due to excessive oscillation amplitudes in the event of resonance . With a periodically recurring excitation, the frequency of which corresponds to a resonance frequency, more and more energy is transferred to the system and stored there ( constructive interference ). The vibration energy is partially removed from the system by damping effects that are always present . If the energy input exceeds the power loss , the oscillation amplitude increases until the load limit is exceeded.

causes

The excitation of the resonance vibrations can take place with an externally predetermined frequency which corresponds to a resonance frequency of the vibrating structure.

Protective measures

To protect the construction, vibration absorbers are installed, which greatly reduce the vibration amplitudes in the area of ​​the resonance frequency and thus dissipate the energy input (e.g. in the tallest structure in 2005, the Taipei 101 , a massive pendulum absorber over several floors). Furthermore, the construction is designed for a natural frequency that typically does not occur during operation. In earthquake areas, one depends on the local typical vibration frequencies of the earth tremors.

On overhead lines , resonance effects can destroy the insulators and lead to electrical short circuits . As a remedy, Stockbridge vibration absorbers are used on the conductors.

Examples

The following cases are known examples of excessive resonance vibrations that have resulted in destruction:

  • On April 12 or 14, 1831, 74 British soldiers marched over the Broughton Suspension Bridge . The bridge collapsed; 40 soldiers fell in the Irwell , 20 of whom were injured and six seriously. Some attribute this to the resonance effect. According to another source, it was probably only the overload caused by the weight of the soldiers that caused the collapse. In order to prevent the potential danger, it is often prohibited and in Germany according to § 27 (6) StVO to march in lockstep over a bridge.
  • When a glass is exposed to sound at its natural frequency , the natural vibration can be excited so strongly that it breaks. This is possible, for example, with a tone generator. The human voice is generally unsuitable for breaking a glass, since neither the necessary sound pressure nor the purity of the frequency can be achieved. In one episode of Mythbusters , singer Jaime Vendera brings a wine glass to a resonance catastrophe with only the help of his voice.

Individual evidence

  1. ^ Ulrich Menschen: Physics and its applications in technology and the environment , 2nd edition Hanser Verlag (2004), p. 100
  2. ^ Johannes Rybach, Physics for Bachelors, Hanser Verlag (2009), p. 57
  3. ^ The Philosophical magazine: or Annals of chemistry, mathematics ..., Volume 9 Richard Phillips, Richard Taylor (p. 385)
  4. ↑ ZEIT series Is it true ?: Bridges can collapse when soldiers march over them in lockstep by Christoph Drösser
  5. ↑ lehrer-online.de : Can you sing glass?
  6. ↑ Meyer Sound Helps Mythbusters Attain Smashing Success. In: Meyer Sound. Archived from the original on February 22, 2006 ; accessed on August 12, 2019 .