PSI - Issue 84

E. Renzi et al. / Procedia Structural Integrity 84 (2026) 1361–1368 E. Renzi et al. / Structural Integrity Procedia 00 (2026) 000–000

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G=2, G=1) may be considered “limited” when it is equal to or less than 50% of the total number of defects detected on the investigated element. Additional specifications are given on the determination of the overall defectiveness based on the defect count on each individual element, which will avoid, by following a purely numerical count, to derive the final judgement overestimating the role of minor components that are present in large numbers: in the absence of specific indications and in order to avoid anomalies in the overall evaluation (especially in the presence of serial element types characterized by a homogeneous level of defectiveness), it is appropriate that the assignment of defectiveness should not be based exclusively on the mere number of elements included in a single subgroup of the substructure or in a single span, but should also take into account the structural relevance of the elements. In order to support operators in their assumptions regarding missing data, some new OI have been introduced to provide indications for cases in which the parameter required for the evaluation is not known or cannot be obtained (for example, the average daily traffic or heavy traffic). Some new OIs clarify the contents of IG more effectively through explanatory tables or graphs. For example, with reference to the influence of design codes on structural-foundational vulnerability, a table is provided that clearly shows the assignment of the parameter “Design class” as a function of span length, year of design, and road design category (OI 4.2.2.4bis). With reference instead to the exposure level of the crossed entity, a table is provided with reference exposure levels for different types of crossed entities (OI 4.2.3.3bis). An important indication regarding the Structural-foundational Warning Class is provided in OI 4.2.4.3, which clarifies that structures that have undergone safety assessments according to Chapter 8.3 of the Italian Technical Standards (MIT, 2018) with a positive outcome may be classified as a ”Low” Structural-foundational Warning Class, provided that it has been previously verified that no significant evolution of the structure's defectiveness has occurred after the date of the assessment. For the seismic Warning Class, OI 4.3.3.1bis is noteworthy, for example, as it clarifies that, for determining the static scheme, span, and material vulnerability class from the specific Table 4.13 of the Guidelines, the reference material may be the deck one, and that in the presence of timber, metal (historic bridges), or mixed steel-concrete structures, reference may be made to the vulnerability values for steel material (always from Table 4.13). OI 4.3.3.1ter highlights that the clear identificat n, following inspections, of the presence of effective seismic resistant elements (such as isolation systems or seismic dissipation devices) may be considered equivalent to the presence of "Seismic design criteria" for the purpose of determining the seismic Vulnerability Class through the Figure 4.5 - Logical flowchart for determining the seismic Vulnerability Class of the Guidelines (partially reported in Fig. 3b). 1.6. Frequency of ordinary inspections The text of the 2022 Operational Instructions did not provide additional guidance or clarifications regarding Chapter 7 – Surveillance and Monitoring System of the Bridge Guidelines . Following the extensive experience gained during the first application period, the need emerged for a more effective management of the periodic inspections outlined in paragraph 7.4.1 – Ordinary Inspections of the Guidelines. The new OI for this section is aimed at capitalizing the established capabilities, resources, and organizational procedures of the road managing entities in the process of surveillance of the infrastructure network, allowing the frequency of ordinary inspections to be adapted to the Overall Attention Class and specific risk sources. To this end, the new I.O. 7.4.1.2 has been introduced, which, for High and Medium-High structural/foundational and seismic Warning Classes, allows the adoption of an annual ordinary inspection program supplemented by intermediate three-months surveillance inspections aimed at monitoring the onset of significant degradation evolution, and must be carried out by adequately trained personnel. In the specific case of hydraulic risk and landslide risk, similarly, some surveillance activities may be carried out by adequately trained personnel as part of the "intermediate" inspections, even though their frequency is not specified and must be evaluated on a case-by-case basis. Furthermore, in the absence of hazard, it is not necessary to repeat ordinary inspections for the related risk. The surveillance personnel who carry out all intermediate inspections must be adequately trained for the types of risk under consideration and expressly assigned to such activities within the regulated surveillance system independently adopted by the Manager.