PSI - Issue 62

Eleonora Bruschi et al. / Procedia Structural Integrity 62 (2024) 299–306 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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more likely to occur. For this reason, preliminary analyses focus on finding voids in the cementitious grout and, on the other hand, on evaluating the potential corrosion of the concrete matrix. Once the number of samples has been defined, it is necessary to locate the investigation points depending on the accessibility of the elements, the presence of warning defects and the critical sections/areas. In the analyzed case, span 3, 4 and 5 were chosen since they are easily accessible with by-bridge. Fig. 6 shows the elements to investigate with information about the level of the defetcs of the PT system, as well as the number of samples to be carried out for each selected element.

Fig. 6. PT elements selected for testing.

Since the available documentation provides information only about the qualitative layout of the cables, but not about their coordinates, cable tracing operations with the Ground-Penetrating Radar (GPR) are necessary to perform the preliminary defect analyses. To obtain the cable layout of Populations A and B, tests must be performed on the blue vertical lines every 50 cm and 100 cm starting from a distance of 90 cm from the beam head, as shown in Fig. 7 (a). At the midspan section, the reference grid is also drawn at the bottom of the beam with horizontal lines transverse to the beam axis, Fig. 7 (b). Regarding Population C, the same test must be perform following the blue grid on diaphragms starting from a distance of 40 cm from the beam side (Fig. 8). Once the cable layout is identified, a preliminary defect analysis can be made combining Ultrasonic Tomography (UST), which is performed by scanning the element according to the red grid, and Borescope (Bor) inspections at the brown spots in Fig. 7 (a). The minimum grid is highlighted in red, while the area in yellow is a possible extension of the grid, depending upon the results obtained from the GPR survey. Bor inspections are performed to verify the presence of the voids identified by the UST, and to investigate the presence of defects in areas that cannot be inspected with UST or characterized by a cable congestion.

(a) (b) Fig. 7. Reference grid to perform the tests on edge and internal beams (a) Side view (b) Bottom view.

Fig. 8. Reference grid to perform the tests on diaphragms