PSI - Issue 84

Pasquale Bencivenga et al. / Procedia Structural Integrity 84 (2026) 264–271

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The dataset includes bridges constructed over several decades, and their construction period, structural typology, and geometric features have been considered. In particular, the presumed design code for each bridge, based on the construction period and recorded in the documentation or, in some cases, inferred during inspection, was evaluated, along with the maximum span length. This analysis revealed that the majority of bridges were constructed between the 1960s and 1990s, in accordance with the Ministerial Circular (1962) and the Ministerial Decree (1980), both issued by the Ministry of Public Works. In particular, approximately half of the analyzed sample was designed according to the 1962 regulations, which correspond to the loads specified in the ANAS internal circular (1952), while one in three bridges followed the 1980 Decree. Only a small portion of the inventory was designed in compliance with more recent standards, such as the Ministerial Decree (D.M. 1990) issued by the Ministry of Public Works, or with earlier post war regulations (1945 Circular). Regarding defect levels (Figure 2b), approximately 20% of the bridges exhibit low defect levels and 48% fall into the medium-low category. These cases, particularly when associated with high safety index values, may be considered of minor concern. In contrast, bridges with medium-high (14%) and medium (18%) defect levels warrant greater attention, as they indicate structural issues requiring closer monitoring and potential maintenance.

100%

100%

MEd,code/MEd,2018 VEd,code/VEd,2018

80%

80%

72%

60%

60%

52%

48%

40%

40%

40%

20%

18%

18%

14%

20%

20%

8%

6%

2% Percentage of bridges [%] 2%

Percentage of bridges [%]

0%

0%

< 0,55

0,55-0,70

0,70-0,85

0,85-1,00

Low Medium-Low Medium Medium-High

Defectiveness level, I D [-]

Internal forces ratios [-]

(a)

(b)

Fig. 2. Occurrence within the considered sample of internal force ratios (for I C estimation) (a), and defect levels (I D ) (b)

On the other hand, the results obtained from the application of the graphical assessment procedure outlined in the previous sections, following the approach proposed by Bencivenga et al. (2022), are summarized in Figure 2a for bending moment and shear, respectively. In the lowest safety index range (I C < 0.55), approximately 2% of the cases are observed for both actions, indicating that only a limited number of bridges exhibit markedly low safety indices. Similarly, the highest safety index range (0.85 ≤ I C ≤ 1.00) includes a relatively small portion of the sample, particularly with respect to shear, confirming that only few bridges achieve high safety levels when evaluated solely on the basis of the original design regulations. The majority of the analyzed bridges are concentrated in the intermediate safety index ranges (0.55 ≤ I C < 0.85), accounting for 58% of the cases for bending moment and 90% for shear. These results indicate that most bridges are characterized by moderate safety margins, reflecting the direct influence of the design standards adopted at the time of construction. Given the large number of cases falling in these intermediate ranges, it is necessary to consider additional parameters to better discriminate safety levels. 3.2. Global structural priority index To support the administrative bodies in prioritizing bridges, the I C value was first transformed into its complementary form, so that higher values reflect the worst-case scenarios. It was then rescaled to the interval [0,1] using inverse min–max normalization according to Equation (2), obtaining I C ,c̅̅̅̅ . The Priority Index I P was then defined as the arithmetic mean of I D and I C ,c̅̅̅̅ , as expressed in Equation (3).