Modal Analysis has been advanced to the point where it can enable the user to, with a high degree of confidence, select an optimum set of modifications that solve a problem analytically. The means to that end are not only very important, but also very critical.
There are three phases to an analysis of this type. First, the test parameters must be determined. Second, the measurements must be taken. This phase is only worthwhile if the first step is done correctly. The third step is the creation of the modal model (parameter estimation). Again, this phase should only be performed if the first two were done correctly.
A usable/accurate modal model is useless, if. not dangerous, if the person exercising it does not understand completely what it means and what the results mean.
This paper addresses the concerns, techniques, requirements, and assumptions often forgotten when using modal analysis to generate a model of a structure.