No abstract

This study examines the use of Rayleigh waves for the detection and sizing of surface-breaking cracks in concrete members. First, finite element simulations are performed to define the conditions for Rayleigh wave propagation in members with rectangular cross-section followed by an experimental study with a concrete beam. Time histories recorded at different locations are 2D Fourier transformed into the frequency-wavenumber domain to enhance interpretation and data analysis. Rayleigh waves form at depths less than half the beam depth. With the introduction of a slot, Rayleigh waves are not observed behind the slot, except for the shortest slot depth, and the slot depth cannot be estimated in the frequency-wavenumber domain. Autospectrum calculations reveal strong Rayleigh wave reflections in front of the slot and by can be used to estimate slot depth when the wavelength is less than half the beam depth.

This experimental study investigates the use of Rayleigh waves for crack detection in structural elements. Receiver arrays measure surface accelerations at various locations with respect to a vertical slot cut into a thin Plexiglas sheet. Two-dimensional Fourier transform calculations provide Rayleigh wave dispersion and energy with respect to various slot depths. In addition, autospectrum calculations aid in defining slot location. It is shown that slots reflect short wavelengths and allow the transmission of long wavelengths. Slot location is easily identified from autospectrum measurements; however, accurate determination of slot depth is dependent on the aperture function of the array.