A novel defect identification and structural health assessment technique

A novel non-destructive defect identification and structural health assessment procedure is presented in this paper. It can detect defects at the local element level of large structures under normal operating conditions or just after a major natural disaster. The procedure is essentially a linear time-domain system identification technique. A structure is represented by finite elements. The procedure tracks changes in the stiffness properties of all the elements in a structure. Since the input excitation information is not available in most cases, the proposed nondestructive evaluation (NDE) algorithm identifies a structure in the absence of such information. Noise in the response information cannot be avoided, and the proposed approach is capable of identifying a structure with noise-laden output response information. With the help of examples, it is shown that the algorithm can identify defect-free and defective structures very accurately even in the presence of noise when excited by earthquake loadings. A real earthquake time history recorded during the Loma earthquake of 1989 is used to excite the structures for verification purposes. Once a defective element is identified in a structure, the exact location of the defect can be identified with the proposed algorithm. The procedure is elaborated with the help of examples. The results indicate that the accuracy of the proposed NDE is much better than other currently available methods even when input excitation information was used for identification purposes. It is established that the proposed NDE method can be used for health assessment of existing structures on a continuing basis or just after a major natural event.