Using a modal test to estimate support properties

A difficulty that occurs when attempting to experimentally-validate a computational model is that one must support the test article in some manner. The dynamics of the support structure must be characterized in order to account for how it changes the overall system response. An experiment does not measure the dynamics of the test article; it measures the dynamics of the test article plus its support structure. This paper derives a technique to estimate the properties of the support structure by performing a modal test for the low frequency range over which the test article behaves as a rigid body. Then the technique is demonstrated for a frame structure supported by 4 air springs.