Damage Assessment of Structures Using only Post-Damage Vibration Measurements

Damage to many structural systems (including bridges, offshore platforms, airplanes and aerospace systems) can occur during normal service due to fatigue loading, a corrosive environment, collisions with extraneous objects, etc. For such structures, in order to guarantee safety, periodic inspections and maintenance are essential: Since undetected damage may result in catastrophic structural failure, the realisation of an accurate and trustworthy damage detection technique is fundamental.Vibration-based inspection offers the potential for detecting faults by monitoring the dynamic response of a structure, exploiting the fundamental principle that structural damage affects the stiffness distribution and hence the presence of the fault will change the dynamic properties of the structure under investigation.Many vibration-based inspection techniques have been developed over recent years which require knowledge of the baseline modal responses of the structure in the original undamaged state.However, for the vast majority of existing structures in operation, such data are simply not available. This keynote presentation reviews past and present research studies in which the author has been involved that aim to detect the presence of structural damage and identify its approximate location, using only post-damage vibration measurements. The techniques presented analyse either the mode shapes, operating deflection shapes or principal orthogonal modes and their corresponding derivatives. These features have been found to be good indicators of damage due to the spatial information that can be provided with respect to location of damage. The methodologies proposed are applied to isotropic/orthotropic uni/bi-dimensional structures and corresponding numerical and experimental results are presented