PSI - Issue 78

Giuseppe Santarsiero et al. / Procedia Structural Integrity 78 (2026) 560–567

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These factors, combined with construction practices typical of the 1960s and 1970s (such as insufficient grout injection into the ducts), make these bridges highly susceptible to degradation phenomena such as corrosion of post tensioning cables, spalling of cover concrete, and oxidation of reinforcement. Key structural characteristics of the viaducts in terms of total length, average span length, number of spans, cross section and profile, are summarized in Table 1.

Table 1. Summary of the case-study bridge dataset.

ID

Cross section

Profile

Length [m] Avg.

Total

Span length [m] No. of

Beams/spans

1 163

33 15/5

2 123

31 18/3

3 260

29 39/9

4 230

33 21/7

5 413

52 20/5

6 140

33 12/4

In this study, only the spans made of prestressed reinforced concrete beams are considered when, for instance, one or more steel deck spans are present. Moreover, it should be noted that the number of beams per span is not necessarily

even over a given bridge. 4. Results and discussion 4.1. Degradation variability within bridges

Fig. 2 shows the Degradation Index (IDeg) values for individual beams across spans in Bridges 4, 5, and 6 (the others are not shown for brevity). The three bar charts compare the Degradation Index (IDeg) of individual beams for Bridges 4, 5, and 6, broken down by span (C1, C2, ...) and beam position (T1, T2, ...), i.e., the first and the last beam of each span are the edge ones. Overall, Bridge 5 exhibits the highest degradation values, with several beams exceeding IDeg = 5, particularly in spans C4 and C2. In contrast, Bridges 4 and 6 show lower overall degradation, with most beams below IDeg = 3, although isolated peaks are still present. Bridge 4 displays a relatively moderate degradation trend, with a maximum IDeg of 4.4 observed in beam T2 of span C2. Notably, the edge beams (T1 and T3), in spans C1 and C2, show higher degradation than central beams, suggesting a more pronounced exposure to aggressive agents along the edges.