Assessment of vibration-based damage identification techniques

In this paper some usual vibration-based damage identification techniques (VBDIT) will be reviewed and used for structural damage evaluation. With the help of a simple supported beam with different damage levels the reliability of these techniques will be investigated. The techniques reviewed herein are based on measured modal parameters which use only few mode shapes and/or modal frequencies of the structure that can be easily obtained by dynamic tests. In other words, by realizing two sets of dynamic measurements, corresponding to two moments of the structure lifetime, the dynamic modal parameters can be obtained. In order to assess properly the performance of these techniques different noise levels are randomly introduced to the response signals of a simulated beam which is exited by a random force. For different levels of damage and noise, the probabilities of damage detection and the probabilities of false alarm for the total number of simulations is evaluated. It can be concluded that among the evaluated techniques the strain energy method presents the best stability regarding noisy signals; however, the detection judgement depends on a threshold level which is discussed in this paper. The change in mode shape curvature, change in flexibility and change in flexibility curvature methods are also capable to detect and localise damaged elements but in the case of complex and simultaneous damages these techniques show less efficiency.