Ground Penetrating Radar (GPR) for bridge inspection

Bridge inspection plays a crucial role in providing bridge operators with an overview of their infrastructure’s current condition, enabling them to extend their service life. This is even more important since a significant number of bridges were constructed after World War II with few comprehensive documents regarding their construction, for example blueprints. In such cases, non-destructive testing (NDT) methods can be employed to investi-gate the structure without causing damage. Among the widely utilized NDT methods, Ground Penetrating Radar (GPR) stands as one of the most widely used methods to localize reinforcement and prestressing strands, thanks to its efficient acquisition capabilities that are characterized by the speed in performing the acquisition and the instantaneous visualization of results. However, due to the inherent complexity, the use of GPR requires qualified and experienced users to obtain high-quality survey data. To assess the capabilities and limitations of GPR, experimental reinforced concrete beams were casted to simulate real-life scenarios. Plastic and metallic tendon ducts were used, and variable spacing between stirrups was adopted. Surveys were conducted using 2GHz bipolar GPR unit, and grid scans were used to maximize the benefit of the GPR. This study presents interesting results in terms of determining the concrete cover, rebar spacings, and the position of tendon ducts accurately. These findings hold significant value for structural engineers who would like to use GPR, especially for bridge inspection applications.