Comparison of the Accuracy of 2D vs. 3D FDTD Air-Coupled GPR Modeling of Bridge Deck Deterioration

Computational modeling is beneficial in the preparation for nondestructive wave-based sensing. Forward models, which can be implemented through a variety of computational modeling techniques, enable parametric evaluations to assess the functionality of a sensor under different conditions, and are integral to the solution of the inverse problem. The focus of this article is on the comparison of two-dimensional (2D) and three-dimensional (3D) Finite Difference Time Domain (FDTD) models. This article gives a presentation of the accuracy of 2D modeling by comparing FDTD simulations of reinforced bridge deck deterioration in 2D and 3D. Simulations for a healthy and delaminated bridge deck are examined. It is shown that the difference in propaga-tion between the 3D and 2D point sources must be considered and is more pronounced at greater distances from the source location. The effect of scattering from the delamination is visible and, while there is variation in amplitude between the 3D and 2D models, the shapes of the resulting waveforms (including the peak arrival times) are well matched.