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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• Relevant Area : it is the area where the bridge is located and where the presence of landslide evidence or precursors is verified (to be inspected carefully). • Approach zone : zone outside and immediately adjacent to the influence zone of the bridge (Fig. 1, Fig. 2). 1.5. Indications about the parameters required by the determination of the Warning Class First of all, it is important to remember that the entire risk classification process through the Warning Classes is based on the collection of information and data relating to the structure within relatively short timeframes, relying on archive documents and visual inspections, and that, as typically occurs for existing structures, such data may be missing, difficult to retrieve, or highly uncertain. In this process, operators must make assumptions regarding missing or unavailable data based on their experience and the specific situation. With the new OI 4.1.3, the intention was, indeed, to emphasize that incomplete knowledge and data uncertainty have a significant influence on the outcomes of the classification and on the economic and risk-related consequences, reminding that in the classification report it is appropriate to highlight which parameters have been “assumed”, particularly with reference to the minimum information required for the evaluation of the Warning Class, and that, before proceeding with the further activities - for example Level 4 Assessment it is advisable to deepen the level of knowledge. With reference to the Structural-foundational Warning Class, the new OI 4.2.2.0 clarifies that, for bridges with a recent construction period or significant maintenance intervention (after 1980), and for which the defectiveness level is low, in the flowchart of IG ( Figure 4.2 – Determination of the structural and foundational vulnerability class ), it is possible to omit the step that applies the aggravation of the vulnerability class due to the rapidity of degradation evolution (Fig. 3). In other words, starting from a low defectiveness level, one may proceed directly to the definition of the vulnerability class considering only the effect due to static scheme, material, and span length (thus without applying the increment that would lead to a medium-low vulnerability class).

(a) (b) Fig. 3. (a) The application of parameter “rapidity of defects’ evolution”, extract from the Figure 4.2.–Calculation of structural-foundational vulnerability class of IG (MIMS, 2022); (b) Application of the parameter “Design criteria” (“seismic/non-seismic”), extract from the Figure 4.5.– Calculation of seismic vulnerability class of IG (MIMS, 2022) Some clarifications and guidance are provided regarding the defectiveness of individual structural elements, offering useful references. For example, it is clarified that the number of defects with medium and low severity (G=3,