Structural identification of a steel frame from dynamic test-data

Structural identification via modal analysis in structural mechanics is gaining popularity in<br />recent years, despite conceptual difficulties connected with its use. This paper is devoted to illustrate both<br />the capabilities and the indeterminacy characterizing structural identification problems even in quite simple<br />instances, as well as the cautions that should be accordingly adopted. In particular, we discuss an application<br />of an identification technique of variational type, based on the measurement of eigenfrequencies and mode<br />shapes, to a steel frame with friction joints under various assembling conditions. Experience has suggested,<br />so as to restrict the indeterminacy frequently affecting identification issues, having resort to all the a<br />priori acknowledged information on the system, to the symmetry and presence of structural elements with<br />equal stiffness, to mention one example, and mindfully selecting the parameters to be identified. In addition,<br />considering that the identification techniques have a local character and correspond to the updating of a<br />preliminary model of the structure, it is important that the analytical model on the first attempt should be<br />adequately accurate. Secondly, it has proved determinant to cross the results of the dynamic identification<br />with tests of other typology, for instance, static tests, so as to fully understand the structural behavior and<br />avoid the indeterminacy due to the nonuniqueness of the inverse problem.