Building Resonance: Structural stability during earthquakes

Why do some buildings fall in earthquakes? 

All buildings have a natural, period, or resonance, which is the number of seconds it takes for the building to naturally vibrate back and forth.  The ground also has a specific resonant frequency. Hard bedrock has higher frequencies softer sediments.  If the period of ground motion matches the natural resonance of a building, it will undergo the largest oscillations possible and suffer the greatest damage. A classroom demonstration follows the animated portion of this video clip.


Keypoints:

What are the key features addressed in this animation?

  • Frequency of a wave refers to the number of waves that pass through a point in one second
  • Period is the amount of time it takes one wave cycle to pass the given point
  • Resonance is the tendency of a system to oscillate with greater amplitude at some frequencies than at others
  • Resonant frequency of any given system is the frequency at which the maximum-amplitude oscillation occurs. 
  • All buildings have a natural, period, or resonance, which is the number of seconds it takes for the building to naturally vibrate back and forth. 

Total Time: 5min 31s
Level: Novice

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