PSI - Issue 84

Pasquale Bencivenga et al. / Procedia Structural Integrity 84 (2026) 264–271

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1. Introduction The structural safety of bridges is a critical issue in Italy due to the widespread presence of aging infrastructure, the increasing traffic demand, and the generally limited maintenance of in-service structures. Many existing bridges were constructed in the mid-to-late 20th century (Salvatore et al., 2026) using outdated design criteria that often underestimate current structural demands. Moreover, environmental factors, such as aggressive exposure conditions and natural hazards, contribute to the progressive deterioration of these structures. Consequently, assessing the safety of bridges has become a priority to ensure public safety and optimize the allocation of resources for maintenance and intervention (Zizi et al., 2023). Traditional bridge assessment methods rely on detailed inspections, extensive data collection, and advanced structural analyses. While these approaches provide highly accurate evaluations corresponding to Level 4 assessments under the Italian Guidelines for Existing Bridges (MIMS, 2022), they are time-consuming and resource-intensive, making them impractical for large bridge networks. There is therefore a clear need for rapid, simplified, and reliable procedures to support decision-making at the network level. Such procedures do not replace detailed analyses but support administrative bodies to prioritize activities and optimize the use of financial and technical resources. According to the Italian Guidelines, preliminary assessments (Level 3) based on comparing internal forces derived from historical and current design codes can be performed; however, this still requires substantial structural information, which may be difficult to obtain, limiting its practical applicability for large inventories. Based on this premise, in the present study an alternative approach to solving such an issue is proposed, which combines the result of on-site inspection and a further-simplified yet reliable Level 3 assessment. This approach allows for a first quantification of structural safety and facilitates the ranking of bridges based on their potential vulnerability. The proposed approach is applied to a set of 50 simply supported bridges in Campania region (Southern Italy), selected according to the extents of the Level 2 of the Italian Guidelines framework applied to a larger stock of about 90 bridges. 2. Methodology 2.1. General The multi-level procedure outlined in the Italian guidelines for existing bridges includes analyses ranging from Level 2, based on typology, exposure, and condition, to Level 4, corresponding to a detailed safety assessment in accordance with current regulations, as specified by Ministry of Infrastructures and Transports (2018). Level 2 aims to determine a potential risk indicator, the attention class, by combining on-site inspection results with other factors through a structured methodological flow. The outcomes of this initial assessment guide subsequent actions for proper management and protection of the infrastructure. Specifically, bridges assigned the highest attention class (high) automatically require a Level 4 assessment, whereas lower classes allow for Level 3 evaluations (medium or medium-high) or periodic inspections for the lowest classes (low or medium-low). It should be noted that Level 3 assessments may also indicate the need for a subsequent Level 4 evaluation based on their results. Applying this multi level risk assessment procedure to a large sample of bridges managed by the same authority, and thus likely exposed to comparable hazards, shows that the key factor determining the need for detailed assessments is vulnerability, which is directly related to the bridge’s condition (representing its residual capacity) and the ratio between design loads and those imposed by recent regulations. Therefore, the procedure proposed in this study aims to synthesize the potential vulnerability of the bridge by combining two main aspects: the condition of the structure, represented by the defect level, which contributes to determining the Level 2 attention class, and the potential structural deficiencies, assessed based on the ratio between the demand defined by the design code and that required by the current regulations.

2.2. Definition of defect level and attention class

The definition of attention class proposed by the current guidelines is, in summary, based on the combination of three main factors: hazard, vulnerability, and exposure. Among these, one of the most influential parameters for determining the attention class is the defect level of the structure, which influences the vulnerability estimation, as