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.
This paper studied how to use the variation of the dispersion curves of Rayleigh wave group velocity to detect interfacial debonding damage between FRP plate and steel beam. Since FRP strengthened steel beam is two layers medium, Rayleigh wave velocity dispersion phenomenon will happen. The interface debonding damage of FRP strengthened steel beam have an obvious effect on the Rayleigh wave velocity dispersion curve. The paper first put forward average Euclidean distance and Angle separation degree to describe the relationship between the different dispersion curves. Numerical results indicate that there is a approximate linear mapping relationship between the average Euclidean distance of dispersion curves and the length of interfacial debonding damage.