Assessing the subsurface condition of glass fiber reinforced polymer (GFRP)-retrofitted
concrete structures is an important inspection problem for the maintenance of reinforced
concrete structures retrofitted with high performance composites like GFRP. The objective
of this paper is to investigate the radar response of GFRP-concrete cylinders through a parametric
study, using the finite difference time domain (FDTD) method. Intact and artificially
damaged GFRP-wrapped concrete cylinders were modeled in a two dimensional domain.
Considered parameters include the thickness of GFRP wrap=layer, width and depth of
artificial defects, and the incident frequency. Modulated Gaussian signals with a carrier
frequency ranging from 8GHz to 18GHz were used as the incident wave. Field and power
responses in both time and frequency domains were investigated. A nonlinear effect due to
the variation of defect dimensions is found in both time and frequency responses, indicating
the multiple, interlayer scattering effect in the system.
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