Quick Assessment of the Bonding Condition of RC Structure Repaired by Epoxy or Cement Bonded Steel Plate using the Dispersive Characteristics of Lamb Waves

摘要

The study provides a new technique to assess the loss of bonding agent, such as epoxy resin or non-shrinkage cement, or peeling of steel plate which bonded to reinforced concrete (RC) structure for strengthening. The interfacial bond is evaluated by the stress waves produced by an impact of a steel ball, usually 1 mm in diameter, and recorded by single receiver 400 mm away from the impact source. The signals are analyzed by the Short Time Fourier Transformation (STFT) and the image of the STFT spectrograms are enhanced by reassigning technique. The result of the finite-element simulation showed the dispersion curve of A0 mode corresponding to the fully bonded three-layered (steel plate-epoxy-concrete) and fully bonded two-layered structure (steel plate-concrete) deviates from the one corresponding to single steel plate in the low frequency region. The presence of substrate layers can better be identified in the wavelength versus group velocity diagram. It was found the slope of the A0 dispersion curve in the wavelength diagram for the wavelength 3 to 8 times of the steel-plate thickness is sensitive to the interfacial condition.