Free-Free, Fixed or Other Test Boundary Conditions for the Best Modal Test?

Deciding on the configuration in which to test a structure is an important consideration which needs to be addressed before a test is carried out. Since the evolution of the modal test, there are several test configurations free-free, fixed, added-mass, amongst othersthat have been developed and used. However, the free-free test configuration remains the most favoured for most applications since it is easy to achieve this configuration in practice. In this paper, different test configurations are compared and their benefits and limitations for the respective applications are discussed. It is also shown by using a simple study that information obtained from a free-free test is not adequate to validate mathematical models for certain applications. In these cases alternative test configurations are suggested and their ability to provide modal information for model validation are discussed.