Natural Vibrations - 4

The Natural Frequency of a Building

The natural frequencies of vibration of a building depend on its mass and its stiffness (or how flexible it is).

The natural frequency for each mode of vibration follows this rule:

f = natural frequency in Hertz.
K = the stiffness of the building associated with this mode
M = the mass of the building associated with this mode

Buildings tend to have lower natural frequencies when they are:

  • Either heavier (more mass)
  • Or more flexible (that is less stiff).

One of the main things that affect the stiffness of a building is its height. Taller buildings tend to be more flexible, so they tend to have lower natural frequencies compared to shorter buildings.

Try some simple experiments with natural frequency.

Taller buildings tend to have a lower natural frequency than shorter buildings.

 

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Vibrating Buildings
       Natural Vibrations - 4

from Bristol University