PSI - Issue 78

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

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Fig. 4. B-scan displaying the recurring stratigraphy generated with GPR Insights.

The orthogonal rebar, which extends only 2 meters on each side of the deck, appears located at the different depths showing an irregular distribution: it appears shallower closes to the edge of the deck as indicated in Figure 5. This pattern suggests an issue more likely related to poor workmanship during construction and concrete pouring, rather than a deliberate feature based on specific design criteria.

Fig. 5. A detail of a C-scan displaying the first layer of 20 x 20 cm square mesh crossed by the orthogonal rebars at 60 cm spacing, which only appear on the side of the bridge where they are shallower as illustrated above. Images generated with GPR Insights.

In addition to the above findings, information related to deterioration assessment was extracted using specific algorithms all based on the analysis of the reflections due to the first layer of rebars. It is in fact well accepted in the industry and detailed into standards [10] that the intensity of the reflection of the rebars is an indicator of the state of the steel itself and its immediate environment. Strong reflections are indicative of a sound reinforced in a protective environment, whereas a local decrease in intensity may be due to actual corrosion and / or a wet saline environment. Figure 7 display the “Auto picking” environment of GPR -Insights, where all first layer rebars are automatically identified by the software (under human supervision) and their depth and intensity are measured.