Tomographic imaging of holographic GPR data for non-invasive structural assessment: the Musmeci bridge investigation

The monitoring of the structural integrity of critical transport infrastructures is extremely important in order to prevent accidents, disasters and ensure urban safety. For this reason, several remote and in situ nondestructive electromagnetic technologies have been exploited as diagnostic tools, from which it is possible to obtain information and images of the infrastructure inner status at different spatial and temporal scales. In this framework, this paper deals with holographic ground-penetrating radar tomographic imaging, used as an in situ diagnostic tool to provide high-resolution images of shallowly buried metallic and dielectric objects. As a matter of fact, the need of integrating information gathered at different scales for a global assessment of the structure health makes the (local and high resolution) image obtained by means of this technique particularly valuable. In particular, we consider the Rascan-4/4000 radar system coupled with a tomographic imaging approach specifically tailored to process holographic data, which is adopted to improve the achievable spatial resolution. A proof of concept of the reconstruction capabilities is given against laboratory data. Moreover, on-field examples in the framework of concrete structures monitoring are shown by processing data collected at the Musmeci bridge in Potenza, Italy.