Damage localization in output-only systems: A flexibility based approach

To assemble flexibility matrices from vibration signals the input most be measured and that there must be, at least, one co-located sensor actuator pair. Techniques to localize damage that use changes in flexibility have not, therefore, found application in the important case of ambient excitation. The central topic of this paper is the discussion of an approach that allows extension of flexibility based damage localization to cases where only output measurements are available. The fundamental idea is that lack of deterministic information on the input can be partially compensated by knowledge of the structure of the mass matrix. In particular, when the inverse of the mass matrix in the coordinates defined by the sensors can be assumed diagonal then matrices that differ from the flexibility by a scalar multiplier can be assembled and these matrices can replace the flexibility with no loss of useful information.