PSI - Issue 78

Guerino Liberatore et al. / Procedia Structural Integrity 78 (2026) 1071–1078

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(tunnels, bridges/viaducts, roads on slopes, cuttings and embankments, road pavement). For each of these components — and subsequently for each network segment — specific fragility curves will be available, implemented using established methods (e.g., HAZUS, SYNER-G, Risk-UE, etc.), based on a preliminary predictive analysis. These curves allow the determination of the probability of damage for the referenced road segment, expressed in terms of damage states (DS1, DS2, DS3, DS4), as a function of the intensity of the seismic event. The estimated damage will take into account: falling debris, landslides, collapse of buildings facing the roadway, damage to the road structure (pavement and embankment), damage to minor works (underpasses and retaining walls), damage to bridges, damage to viaducts, and damage to tunnels. A network segment may also include two or more vulnerable components (e.g., a viaduct and the road body), each characterized by its own fragility curve, specific to the type of structure/infrastructure involved. The probability of damage for individual network segments will then be associated — via algorithm — with a Performance Index (PI), which can be classified as ordinary, functional, compromised, or critical.

Table 1. Performance Index (PI) Performance Index (PI)

Description

Operational Scenario

Color Green

Ordinary

No damage or negligible damage

Full usability without restrictions

Functional

Minor damage

Usability with no significant impact on speed or capacity Usability possible with mitigation measures Road unusable due to lack of safety

Yellow

Compromised

Moderate damage

Orange

Critical

Severe or extensive damage

Red

This index will be graphically represented on the situational dashboard, in a GIS environment, using linear elements in different colors (green, yellow, orange, and red), according to the categorization shown in the table 1. For network sections classified with a Performance Index of “ordinary” or “functional”, the algorithm assigns a scenario characterized by the absence of damage and/or minor damage, such that the road can be safely used without reductions in speed or capacity. For network sections classi fied as “compromised”, the scenario reflects the lack of absolute safety, but passage remains possible with suitable mitigation measures (e.g., load restrictions, lane reductions, temporary bypasses). For “critical” sections, the scenario indicates the com plete absence of safe conditions, making the road effectively unusable. The situational dashboard will also be capable of interacting with AINOP, ensuring an up-to-date inventory of all surveyed structures and infrastructures and immediate access to the most significant assessment outcomes stored in the archive. This information can be used, for instance, in the process of updating fragility curves. The proposed methodology is characterized by a probabilistic matrix, in which the likelihood of damage is clo sely linked to the seismic event’s intensity. For this reason, it is still essential for road network operators to act promptly, deploying specialized technical teams equipped with specific tools to confirm or revise the actual functional status of each road segment through standardized on-site inspections. These inspections will follow the routes generated by the system, prioritizing primary routes (those with the shortest travel time) and segments with a high probability of damage. In this way, the preliminary road network scenarios, initially established based on the algorithm-assigned Performance Index, can be verified and updated. At that point, the situational dashboard will provide a realistic and updated graphical representation of both usable and unusable roads. Once this reconnaissance is completed, the operators will proceed to carry out, as quickly as possible, the minimum essential interventions to restore road traffic, thus ensuring Operational Continuity. 5.3. VISIT methodology The ad hoc inspections following a seismic event must be accurate, fast, and standardized to support emergency response effectively. The VISIT approach (Visual Inspection for Safety-Deficit Identification and Triage), developed by ANSFISA and the University of Udine (Grimaz et al., 2025b, 2025a, 2024b, 2024a), meets these requirements. It