Characterization of the crack depth in concrete using self-compensating frequency response function

Concrete structures typically have cracks due to the brittle characteristics of the material. In order to check their severity in an existing structure, the crack depth should be evaluated with nondestructive testing such as the wave transmission method. The method determines the crack depth using the energy of the Rayleigh wave propagating over the crack and needs a reliable technique to evaluate the wave energy with measured surface waveforms. This paper proposes a self-compensating frequency response function to improve isolating the Rayleigh wave components from the accompanying noise. A rigorous procedure using the spectral estimator for noisy measurement is derived for self-compensating. The proposed technique was verified with experimental application to structural cracks as well as artificial notches.