3-D finite-difference time-domain modelling of ground penetrating radar for identification of rebars in complex reinforced concrete structures

This paper presents numerical and experimental investigations to identify reinforcing bars using the ground penetrating radar (GPR) method. A novel element of the paper is the inspection of different arrangements of reinforcement bars. Two particular problems, i.e. detection of few adjacent transverse bars and detection of a longitudinal bar located over or under transverse reinforcement, have been raised. An attention was also paid to the influence of few adjacent bars on the estimation of wave velocity in concrete based on the diffraction hyperbola. The GPR simulations were undertaken using the finite-difference time-domain (FDTD) method. The new approach for the numerical modelling of GPR in complex reinforced concrete structures with the use of a 3-D FDTD model was presented. Simulated scans for the 3-D model were compared with results of in situ surveys. The results of investigations showed high usefulness of the 3-D model for the GPR field propagation in structures with a complex system of the reinforcement.