PSI - Issue 84

M. Cademartori et al. / Procedia Structural Integrity 84 (2026) 384–391

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The most widely used construction technology amongthis network,requiring a safety assessment,isthe Prestressed Reinforced Concrete, which, divided into Post-Tensioned (35%) and Pre-Tensioned (23%), accountingfor 58% of the total. As expected, OrdinaryReinforcedConcrete structures account for 17%, while Composite Steel–Concrete technology, which, although generally more recent, represents the 16%. Finally, Masonry structures make up 7% [Fig. 4].

Fig. 4. Bridge stock grouped by material and technology

Fig. 3. Bridge stock grouped by span number

3.2. Presentation of the main results and outcomes based on the portfolio of bridges analyzed In order to understand the main issues affecting this bridge portfolio, it is useful and interesting to refer to the

classes of attention [Fig. 5] defined in accordance with the Guidelines. In the Structural and Foundational category less than 50% are classified as high and 20% as medium-high; in the Seismic the 66% is represented by both high and medium-high levels; in the Hydraulic the level is mainly low (51%) or high (37%), with no significant intermediate levels, and Landslides, predominated by the low level with the 41%. It should be noted that the identification of the class of attention assigned to a structure is a step usually carried out by the infrastructure managing authority and is an input parameter for the designer. In order to present the results of the assessments

carried out, it is necessary to describe the methodology through which they were obtained. The software tools used are commercial ones; most of the analyses are linear, except for some seismic analyses performed using the pushover method. The modelling strategy was always aimed at achieving both reliable results through adequate discretization of the structural elements and models maintaining a reasonable computation time, generally favouring the use of beam elements over shell elements, except in the case of massive slab bridges, local-level modelling of slabs and abutments. Finally, the assessment itself was carried out using the sub-components approach (Priestley, 1996), which, by subdividing the structure into sub-components, makes it possible to identify the most vulnerable elements [Fig. 6] and to characterize their failure mechanisms of the deck element [Fig. 7]. The results of the assessments, although in some cases predictable given the conditions of certain structures, are as follows: most of the superstructures [Fig. 8] fall under the 44-ton category (45%), corresponding to the load prescribed by the national road traffic code with the relevant safety coefficients. This is followed by the operative category, accounting for 32% of the sample, which corresponds to the load defined by the NTC18 with material- and action-side coefficients that are less conservative in terms of safety compared to the adequate category, which represents only 2%. The 44-ton not achieved category includes all cases in which the road code load is not reached (14%). In this figure some intermediate cases could be also identified, as the case of a reduction in the applied load combined with partial carriageway restrictions, such as Fig. 5. Classes of Attention of the bridge stock