| Detection and characterization of damages in civil structures is vital for public safety. Microwave/radar NDT (Nondestructive Testing) techniques are suitable for in-depth assessment of concrete structures since electromagnetic waves can penetrate into dielectric materials like concrete. Ground penetrating radar (GPR) is one of the commonly used microwave/radar techniques for concrete structures. Numerical simulation provides valuable insights to understand the wave propagation and scattering phenomena in the GPR applications for subsurface defect detection and characterization. In this thesis, Finite Difference Time Domain (FDTD) methods are used. Delaminations with different sizes and at different depths inside a rectangular concrete slab with different dielectric properties are modeled. From the simulation results, it is found that delaminations are detectable in all cases. Moreover, the curvature values of arch-like shapes obtained from B-scan images of concrete slabs are calculated. It is shown that the curvature value and the size of delamination are related. Finally, a procedure for estimating the size of subsurface delamination in concrete slabs is proposed. |
