PSI - Issue 78

Irene Matteini et al. / Procedia Structural Integrity 78 (2026) 992–999

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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 Survey The entire bridge was scanned using a MCGPR GS9000/GX1 Proceq during the springtime and was carried out in two hours with limited road closures, allowing for a highly efficient operation and minimal impact on local traffic. This device 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.

The survey was limited to the concrete deck and was conducted with a 1 cm step size (inline data spacing) in 45 min collecting twelve 32 m-long swaths in a zig-zag pattern. The weather condition on the survey day were recorded with an average temperature of 10 degree Celsius, and sunny. No precipitations were recorded within 5 days prior the survey. 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, 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 • Linear gain and Time Gain Compensation