Performance of vibration-based techniques for the identification of structural damage

Early detection of damage is of special concern for civil engineering structures. If not identified in time, damage may have serious consequences, both safety related and economic. The traditional methods of damage detection include visual inspection or instrumental evaluation. A comparatively recent development in the health monitoring of civil engineering structures is vibration-based damage detection. Vibration characteristics of a structure, that is, its frequencies, mode shapes, and damping are directly affected by the physical characteristics of the structure including its mass and stiffness. Damage reduces the stiffness of the structure and alters its vibration characteristics. Therefore, measurement and monitoring of vibration characteristics should theoretically permit the detection of both the location and severity of damage. However, in practice, a number of difficulties persist in vibration-based damage identification. As a result, most of the damage identification algorithms fail when applied to practical civil engineering structures. This article presents a survey of some of the more commonly used algorithms and describes the conditions under which they may or may not work. The success of individual algorithms is measured through computer simulation studies. It may, however, be noted that additional practical difficulties that cannot entirely be reproduced through computer simulation exist, which makes vibration-based damage identification a challenging field with many unanswered questions.