Damage Detection in a Structural System Via Blind Source Separation

Abstract eng:
A technique for vibration based system identification for detection of earthquake induced damage in structural systems is discussed. A numerical case study of detection of damage in a building frame subjected to a strong earthquake is presented for the application of a blind source separation algorithm to the problem of output only modal identification. The problem of base-excitation, as in earthquake loading, presents a situation wherein the governing equation of motion is usually formulated in terms of the deformations relative to the base motion whereas the response recordings are of absolute acceleration. The conditions under which the blind source separation formulation of representing observed system response as a mixture of independent sources can be adapted for the case of base excited systems are discussed. The modal parameters (mode shapes, natural frequencies,) are extracted from the vibration response and the changes in the identified modal parameters are tracked in time through a moving time-window analysis. The implications of the assumptions in the formulation and their validity in practical problems is also discussed.

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