Structural Dynamics - Modal Analysis

Modal Analysis

A modal analysis calculates the frequency modes or natural frequencies of a given system, but not necessarily its full time history response to a given input. The natural frequency of a system is dependent only on the stiffness of the structure and the mass which participates with the structure (including self-weight). It is not dependent on the load function.

It is useful to know the modal frequencies of a structure as it allows you to ensure that the frequency of any applied periodic loading will not coincide with a modal frequency and hence cause resonance, which leads to large oscillations.

The method is:

  1. Find the natural modes (the shape adopted by a structure) and natural frequencies
  2. Calculate the response of each mode
  3. Optionally superpose the response of each mode to find the full modal response to a given loading

Read more about this topic:  Structural Dynamics

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