Any physical system can vibrate. The frequencies at which vibration naturally occurs, and the modal shapes which the vibrating system assumes are properties of the system, and can be determined analytically using Modal Analysis.
Analysis of vibration modes is a critical component of a design, but is often overlooked. Structural elements such as complex steel floor systems can be particularly prone to perceptible vibration, irritating building occupants or disturbing sensitive equipment.
Inherent vibration modes in structural components or mechanical support systems can shorten equipment life, and cause premature or completely unanticipated failure, often resulting in hazardous situations. Detailed fatigue analysis is often required to assess the potential for failure or damage resulting from the rapid stress cycles of vibration.
Detailed seismic qualification also requires an understanding of the natural vibration modes of a system, as the large amount of energy acting on a system during seismic activity varies with frequency.
Detailed modal analysis determines the fundamental vibration mode shapes and corresponding frequencies. This can be relatively simple for basic components of a simple system, and extremely complicated when qualifying a complex mechanical device or a complicated structure exposed to periodic wind loading. These systems require accurate determination of natural frequencies and mode shapes using techniques such as Finite Element Analysis.