An Examination of Instantaneous Frequency as a Damage Detection Tool

Introduction Research on vibration based damage identification has been expanding rapidly over the last decade. Much of the focus of this research has been placed on damage detection based on comparison of system properties 'before' and 'after' damage under the premise that the system can be treated as linear in both states. It is worth noting that in this approach the type of ‘damage’ that can be identified is restricted to that which has an influence in the small amplitude vibration characteristics of the system. Severe inelastic response during an extreme event in a system idealized as elasto-plastic, for example, is not detectable in this approach to the problem. Furthermore, even for the type of damage that can be handled by the before and after strategy, separation of structural from nonstructural damage may be very difficult from examination of the small amplitude signals that can be obtained for Civil Engineering Structures in service.