Welded I-section steel members are widely used in engineering, and it is prone to fatigue damage at the web/flange junction under cyclic load. Due to the sudden damage and the heavy losses, it is necessary to detect the damage in time. Based on the study of stress wave propagation mechanism in steel beam, a broadband impact wave is generated by a hammer striking on the surface of a steel I-beam, and the fiber interferometer is attached to the surface of steel beam to receive the stress wave signal. By analyzing the impact echo signal spectrum with FFT, the existence and location of the damage is determined. Experimental results show that it is feasible to detect the damage at the flange/web junction of the steel I-beam by impact-optic method.
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