DETECTING AND LOCATING DAMAGES IN COMPLEX STRUCTURES BY THE SYSTEM IDENTIFICATION TECHNIQUE (NONDESTRUCTIVE TEST, INTEGRITY, DYNAMIC RESPONSE, PARAMETER ESTIMATION)

Two new methods of identifying crack locations in complex, continuous structural systems by investigating the changes in the mass and flexibility matrices are presented. These two matrices can be obtained by applying the System Identification Technique to the measured dynamic response of the system under either impulse or random forcing function. Theoretically, the above two matrices can also be obtained by the finite element method and system reduction technique if the real damage size in the structure is known. Initially, analyses by the finite element method are made for cases with several different crack locations and boundary conditions in a steel beam. An experiment using an aluminum beam with different size cracks has also been conducted to verify the proposed technique. Similarly, the finite element models of a square plate with hole or crack damage and a 1/14 scale offshore platform with a through cut in one secondary horizontal member were analyzed.; Simplicity in both on-site measurement and analysis makes the technique particularly useful for real time applications.