PSI - Issue 62

4

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

302

Three different populations of PT cables are identified and shown in Table 1.

Table 1. Populations of PT cables. It is worth mentioning that the composition of the smaller cable of Population B (indicated with the * in Table 1. is unclear due to inconsistencies in the table. 14 Edge beams 14 Internal beams 28 Diaphragms Total cables Population A 5 cables 42 ɸ 5 4 cables 42 ɸ 5 - 126 cables 42 ɸ 5 Population B - 1 cable 26 ɸ 5 or 13 ɸ 5* - 14 cables 13 ɸ 5 or 26 ɸ 5 Population C - - 2 cables 26 ɸ 5 56 cables 26 ɸ 5 The PT system defectiveness is obtained by considering for each span all the elements (beams and diaphragms) belonging to it. In this case, by filling out Level 1 forms provided by the Italian Guidelines, the overall defectiveness turned out as medium-low. In addition, no elements with clear defects, such as compromised ducts, corroded wires or loss of prestressing force, were identified. On the other hand, visual inspections have shown anchors in a poor state of preservation, with the presence of humidity and corrosion, due to the deterioration and permeability of joints (Fig.4).

(a) (b) Fig. 4. (a) Anchors of beam 4, span 6 (b) View from the bottom of joint 7 at beam 4, span 6

The following procedure, used to determine the number of cables to investigate, must be applied to each of the three populations of cables present in the structure with homogeneous characteristics in terms of typology, geometry, and length. The procedure mainly consists in the definition of the Risk Class R and the Impact Degree I. The Risk Class R is determined by crossing two parameters, namely the Probability Index P, which suggests the probability of having defects inside the cable, and the Consequence Index C, which expresses the consequence of a cable crisis on the entire structure. Both the parameters can assume a score between 1 and 5 and they are determined by considering influencing factors expressed tabularly (paragraph 2.1.4 of Special Inspection). Mathematically, the Probability Index P and the Consequence Index C are the results of the weighted sum of the score of the single influencing factor multiplied by its weight (w i ). As an example, the influencing factors related to Population A are reassumed in Table 2 along with their scores. In general, influencing factors as “PT system defectiveness” and “bridge relevance with respect to the road network” are the same for all cables populations, because they do not depend on the type of cables, but are related to the infrastructure under consideration. The same scores are assigned to Population A and B, as these two populations