Airborne and ground penetrating radar systems for condition assessment of civil infrastructures: Fid-Bau Portal

Airborne and ground penetrating radar systems for condition assessment of civil infrastructures

Büyüköztürk, O. / Yu, T.T. / Giannopoulos, A. / Forde, M.C. / Padaratz, I.J.

Two types of radar for civil engineering applications are discussed in this paper; airborne and ground penetrating radars (GPR) which are distinguished by the transmitting medium (airborne: air, GPR: soil/rock). Basics of radar systems are introduced, followed by an overview of radar applications in civil engineering. The performance of radar systems is also defined and discussed, with emphasis on the resolution calculation. It is shown that airborne radar systems provide an opportunity for remote investigation of concrete materials. The signal processing algorithm of Synthetic Aperture Radar (SAR) enables very high frequency airborne radar systems to be frequency turned. A parametric analysis was undertaken using the generalized equation for velocity and has shown that lower frequency GPR systems are more vulnerable to velocity reduction due to lower frequencies as conductivity increases - compared to high frequency airborne systems. It was concluded that the simplified velocity equation may be valid for high frequency airborne radar, but may not be stable for the lower frequency GPR systems - subject to the conductivity of the medium under investigation. A further parametric study has demonstrated the relationship between antenna centre frequency, corrected for ground coupling frequency reduction, and target resolution. A case study has demonstrated the effectiveness of GPR in detecting voids in grouted plastic tendon ducts in post-tensioned bridge beams. The importance of bow-tie antenna orientation was demonstrated.