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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5

differ only in the cable composition. However, for Population C, the scores of influencing factors “cable length and geometry” and “redundancy of the PT system” vary, since it differs from A and B not only in composition but also in the geometry of the route (linear layout) and in the length of the cables.

Table 2. Probability Index and Consequence Index for the example case of Population A Availability of original documentation (w i = 0,15)

Cost for repairing or replacing the cable (w i = 0,40)

It is known the number of cables and the qualitative layout from the documentation Cable length and geometry (w i = 0,40)

3

High

4

Redundancy of the PT system (w i = 0,40)

The loss of some cables inevitably leads to the collapse of the structure Bridge relevance with respect to the road network (w i = 0,20) 5

Long cables with small curvature

3

PT system defectiveness (w i = 0,45)

Medium-low

2 3

Non-critical work

3 4

Probability Index P

Consequence Index C

The Risk class R is determined by crossing the two parameters using the matrix shown in Fig. 5; in the case of Population A, R turns out medium.

Fig. 5. Matrix for the definition of the Risk Class R.

The second parameter under consideration is the Impact Degree I that the cables inspection has on the overall structure. The Impact Degree could be low, medium or high: it is low when the tests are minimally invasive, while it is high when investigations include destructive tests (IGSI). In this case, the impact is considered medium because the chosen combination of investigations includes extensive non-destructive tests and semi-destructive investigations. The Risk Class R and the Impact Degree I are therefore used to define the maximum acceptable percentage of potentially defective cables in the sample (Tab. 13 of IGSI). Once defined, the number of samples can be determined to ensure that this percentage is verified, with a confidence level of 75% (Tab. 14 of IGSI). Referring to the total number of cables for each population of Table 1, it turns out that the number of samples to be investigated is equal to 6 for Population A and C, while it is 5 for Population B. During the visual inspection no elements with clear defects were detected, otherwise the in-depth analysis required in Phase 2 should be carried out directly for these elements. 2.2. Phase 1: preliminary analysis The corrosion of the cables is considered the most critical defect as it can result in section loss and ultimately breakage of metal strands. Grout’s defects, such as voids, water infiltration, and compromised grout , make corrosion