Ground Penetrating Radar Data Processing for Concrete Bridge Deck Evaluation

Abstract

This paper presents ground-coupled ground penetrating radar (GPR) data-processing procedures for concrete bridge deck evaluation. GPR signals are analyzed in the depth range from the concrete surface to top reinforcement mat. Although most ground-coupled GPR analysis methods focus on the attenuation of signals from rebar reflections only, the proposed algorithms extract three types of parameters from GPR scans: Direct coupling amplitude, wave velocity in concrete cover depth, and normalized, depth-corrected GPR signal amplitude from rebar reflections. These parameters provide information about bridge deck deterioration conditions at different depths. First, the signal amplitude of the direct coupling wave on the concrete surface is analyzed over the entire bridge. Second, the wave velocity in cover concrete is obtained through migration of rebar reflections, and then the rebar depth can be calculated. Third, signal attenuation in concrete is calculated from the rebar reflection and further corrected by the rebar depth. In addition, the true time zero for GPR signal analysis is validated by numerical simulation and experimental data. Finally, this algorithm is demonstrated on field testing data, and the final results are presented in the forms of direct coupling wave amplitude, wave velocity, and attenuation maps.