PSI - Issue 64

Marco di Prisco et al. / Procedia Structural Integrity 64 (2024) 2133–2140 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 2. CFRP retrofitting system: a) longitudinal and b) transversal section.

3. The diagnostic carried out In order to identify the material properties of the bridge components as well as the details, an ad – hoc diagnostic campaign was performed on the bridge structural elements. In particular, 6 concrete cores (red points in Figure 3) were extracted from piers (4 cores) and from beams (2 cores) in order to measure both the compressive strength of the material and the carbonation state of the concrete. The average compressive strength obtained was equal to 58.1 MPa for the piers and 67.6 MPa for the beams. The cores extracted from the piers did not exhibit any carbonation, while the cores extracted from the beams (that were extracted across the whole web of the beam) exhibit an average carbonation depth of 14 mm and of 40 mm respectively facing the internal of the external part of the bridge. The detailed results are available in Table 1. Additional non-destructive tests were performed in the points highlighted with green points in Figure 3. In each of these points the rebound index and the Ultrasonic Pulse Velocity (UPV) were measured and the hardness tester technique was used to estimate the steel strength of the reinforcement in the structural elements. It is worth to note that the rebound index, when compared with the results of compressive tests on cores, provides a significant overestimation of compressive strength prediction for the case of the piers (average value of the rebound index estimation equal to 77 MPa), while, on the contrary, significantly underestimates the compressive strength in the case of the beams, where the average rebound index estimation of the compressive strength is equal to 34.15 MPa. In a similar way, the UPV measurements, direct in the piers and indirect in the beams, provide respectively an average speed of 4.04 km/s and of 3.68 km/s. The low values obtained with non-destructive tests on beams could be related to probable superficial weakness of the mortar layer casted to restore the concrete cover.

Figure 3. Lateral view of the bridge where the investigation areas are indicated (non-destructive tests in green, destructive tests in red).