PSI - Issue 84

Irene Matteini et al. / Procedia Structural Integrity 84 (2026) 677–685

680

During the first phase, an initial inspection was carried out following the Italian Regulation provided by the Ministry of Public Works [8] for bridge inspection including Level 1 and 2. The inspections were conducted from the ground with limited access. From the visual inspection, delaminated areas and spalling were observed on the underside of the concrete deck and along the arch beams, particularly in the middle area of the deck and on the outer beams. Bio-growth and water stains were observed on the outer face of the arch beams, and on the abutment walls. On the underside of the concrete deck, area with efflorescence and water stains were also observed (Figure 1b). 2.2. MCGPR Surveys The entire bridge was scanned using a Proceq GS9000 with GX1 antenna array module through two surveys, one conducted in the winter and a second one in the summer of the same year. Each survey was completed within approximately two hours, with limited road closures, ensuring a highly efficient operation and minimal impact on local traffic. For both surveys, the same device is used and is equipped with 35 antennas in a VV polarization with 2.5 cm spacing and 15 antennas in a HH polarization with 5.5 cm spacing, along a total width of 85 cm. All antennas are based on the Stepped Frequency Continuous Wave (SFCW) measuring principle [9], working in the 500 – 3000 MHz interval.

Fig. 2. (a) General photograph of the bridge deck showing the presence of cracks visible from the asphalt layer (Matteini); (b) 3D Global positioning of the scans. Image obtained from GPR Insights software.

The periodic surveys were completed to establish a database to use for monitoring and assisting the agency for the maintenance of the structure. The surveys were limited to the concrete deck and were conducted with a 1 cm step size (inline data spacing) in 45 minutes collecting twelve 32 m-long swaths in a zig-zag pattern. The weather condition on the survey day was recorded showing no precipitations recorded within 5 days prior to the surveys. Since the system uses GNSS and real-time visualization, no time was spent on setting up a grid. In addition, as previously mentioned, no X-Y data collection is needed due to the high channel density and dual polarization, reducing time in the field. Raw data was then post-processed in GPR Insights [10], a proprietary software developed by Screening Eagle for advanced visualization and data analysis. The radar signal processing sequence included the following steps: • Time zero cut-off • Data trimming after 14 ns • Bandpass filtering • Horizontal background removal