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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critical issues arising from the L2 analyses resulting in a High or Medium-High Warning Class, and contains the tables for the re-evaluation of the Warning Class (Fig. 1).

(a) (b) Fig. 1. “VAL 3– Hydraulic” assessment (a) in case of special inspections; (b) in case of a High or Medium-High hydraulic Warning Class 1.4. Improvement of landslide inspection and risk classification procedures The new Operating Instruction 3.6.5 provides a guidance for special inspections in areas with evidence of landslide phenomena (according to § 3.6 of IG), namely, in cases where there is uncertainty in the assessment of the following parameters: presence of potential landslides; landslide extent or volume; landslide velocity; bedrock depth and cover thickness; Extent of the landslide-bridge interference; or in cases where bridges interact with landslides stabilized by mitigation works; structural signals attributable to bridge–landslide interaction; presence of potential source areas of rapid/extremely rapid landslide phenomena.

Fig. 2. Graphical clarification about the definition of direct and indirect landslide-bridge interference (Perilli et al., 2024); influence zone of the bridge and Approach Zone according to the new Operating Instructions 4.4.1.2. and 4.4.3.1.

In this regard, three supplementary annexes are provided: Annex B_Bis_Level 1 Landslide Inspection Form (which supplements the existing form); Annex D_New Special Landslide Inspection Form ; Annex G_Special Inspections and Investigation Plan relating to landslide risk. The Operating Instructions 4.4.2.5bis, 4.4.2.7bis, 4.4.2.8bis, 4.4.3.1, identify the areas to be studied to enable a more appropriate assessment of the primary and secondary parameters involved in the evaluation of susceptibility related to landslide risk: • Diagnostic Area : sufficiently broad to allow characterization of the geomorphological and geological context (to be examined through documentation and cartography). • Geomorphological Significant Area : it represents the spatial extent where it is possible to identify and analyze geomorphological, lithological and environmental evidence of landslide phenomena.