Rayleigh wave propagation and scattering characteristics at debondings in fibre-reinforced polymer-retrofitted concrete structures

Structural health monitoring is of paramount importance to ensure safety and serviceability of structures. Among different damage detection techniques, guided wave–based approach has been the subject of intensive research activities. This article investigates the capability of Rayleigh wave for debonding detection in fibre-reinforced polymer-retrofitted concrete structures through studying wave scattering phenomenon at debonding between fibre-reinforced polymer and concrete. A three-dimensional finite element model is presented to simulate Rayleigh wave propagation and scattering at the debonding. Numerical simulations of Rayleigh wave propagation are validated with analytical solutions. Absorbing layers by increasing damping is employed in the fibre-reinforced polymer-retrofitted concrete numerical model to maximise computational efficiency in the scattering study. Experimental measurements are also carried out using a three-dimensional laser Doppler vibrometer to validate the three-dimensional finite element model. Very good agreement is observed between the numerical and experimental results. The experimentally and analytically validated finite element model is then used in numerical case studies to investigate the wave scattering characteristic at the debonding. The study investigates the directivity patterns of scattered Rayleigh waves, in both backward and forward directions, with respect to different debonding size-to-wavelength ratios. This study also investigates the suitability of using bonded mass to simulate debonding in the fibre-reinforced polymer-retrofitted concrete structures. By enhancing physical understanding of Rayleigh wave scattering at the debonding between fibre-reinforced polymer/concrete interfaces, this study can lead to further advance of Rayleigh wave–based damage detection techniques.