PSI - Issue 84

Vittorio Palma et al. / Procedia Structural Integrity 84 (2026) 630–637

632

indicators referable to vulnerability, hazard, and exposure, representing respectively the propensity of the asset to develop limit states, the severity of actions and environmental contexts, and the functional consequences on the transport network (Ministero delle Infrastrutture e dei Trasporti (MIT) 2020). Within this framework, three decision problems are defined, corresponding to different phases of the assessment pathway and to different levels of available information. The first concerns the programming of special inspections for post-tensioned prestressed concrete bridges (Planning Level 1), driven primarily by the vulnerability of the post-tensioning system. The second addresses the programming of safety assessments (Level 4; Planning Level 2), governed by the presence of critical conditions and by the level of structural–foundation defectiveness, with the integration of overall hazard and exposure indicators. The third decision problem relates to the prioritisation of local interventions aimed at restoring or improving durability, conceived as a short-term management tool integrating degradation conditions and user safety reports. From a formal perspective, the three modules share a common decision architecture based on a rule-based and predominantly non-compensative Multi-Criteria Decision Making (MCDM) approach relying on ordinal variables. For each bridge , a discrete priority class ∈ {1,…,5} is assigned through monotonic mappings governed by a dominant guiding parameter. The ranking within each priority class is subsequently refined through a vector of indicators and a lexicographic comparison. Within this structure, the dominant variable determines the primary priority class, while secondary indicators, such as hazard and exposure, are used exclusively to discriminate assets within the same class, ensuring transparency, consistency, and reproducibility of the prioritisation process. The following sections describe the three modules in detail, programming of special inspections, programming of safety assessments (Level 4), and prioritisation of local interventions, and formalise their respective criteria and decision rules. 3. Methodology for the programming of special inspections The Guidelines prescribe, for post-tensioned prestressed concrete bridges, the execution of special inspections aimed at assessing the condition of the post-tensioning system prior to detailed safety assessments (Level 4), due to the potential presence of defects not detectable through ordinary visual inspections. Accordingly, Planning Level 1 defines a network-level programming criterion that assigns each asset a priority class driven by the vulnerability of the post-tensioning system, subsequently refined through typological and contextual indicators. The guiding parameter is the level of defectiveness of the post-tensioning system, , defined at deck or span level as a synthesis of the condition ratings assigned to individual system components as a function of severity, extent, location, and the possible presence of critical conditions (Mazzatura, Caprili, et al. 2023; Celati et al. 2025). When at least one element exhibits High or Medium–High defectiveness, or when critical conditions are identified at deck level, the system is assigned the highest observed level; otherwise, the overall class is determined based on the distribution of defectiveness levels among the inspected elements. A discrete priority class ∈ {1,…,5} (with =1 indicating the highest priority) is directly associated with through a monotonic mapping consistent with a precautionary logic: = ( ), : { Low ,…, High } → {5, … ,1}. (1) The primary prioritisation is therefore governed by a classification based on the vulnerability of the post tensioning system, rather than by a compensatory score. Once the class has been assigned, the ranking within the same class is refined through a vector of indicators , representing intrinsic structural fragility, the extent of degradation, and the expected impact on the transport network: Π =( , ), =( , ( ) , , ˉ , / , ). (2) Within , the indicator describes the intrinsic criticality of the structural typology, derived from the combination of static scheme, redundancy, and construction methodology, allowing robust configurations to be distinguished from more fragile ones. The term ( ) represents the number of post-tensioning elements classified with High or Medium–High defectiveness and discriminates between localised and widespread degradation; an