Assessing Voided Reinforced Concrete by Numerical Modelling of Impact-Generated Rayleigh Waves

Concrete structures require routine inspections. Within elastic wave-based non-destructive testing methods, the Rayleigh wave (R-wave)-based method shows great potential in defect characterisation with only one-side access required. This paper aims to investigate the effect of different locations and densities of voids on R-waves using a 2D finite element model. The numerical model was validated and calibrated with experimental results to increase the reliability and representativeness of the model developed. The difference between the R-wave velocity obtained from the numerical model and theory was within 5%, while the correlation between the R-wave waveform collected from the numerical and experimental data was 0.975. The developed numerical model was used to carry out a series of parametric studies investigating the relationship between different R-wave properties and void characteristics. The results revealed that the 5 kHz velocity index was the most sensitive for distributed void identification, with solid correlations up to 0.9879 reported. The correlations obtained from the data analysis suggest good feasibility of the demonstrated computational approach in evaluating the effect of defects in concrete on R-wave behaviour. This approach also offers useful insights into developing an alternative assessment methodology for internal damage localisation and characterisation utilising elastic wave measurements.