PSI - Issue 84

L. Zoccolini et al. / Procedia Structural Integrity 84 (2026) 167–174

169

tensioned bridges, aimed at identifying potential degradation mechanisms, estimating their likelihood of occurrence, and assessing their consequences for structural safety, functionality, and socio-economic impact. Its goal is to establish a hierarchy of priorities among structures and individual structural elements, allowing managers to identify in a consistent manner situations that require immediate intervention, further inspection, or monitoring over time. By introducing specific synthetic risk indicators, the CS465 also aims to promote a consistent approach to the management of post-tensioned concrete bridges, reducing reliance on subjective assessments and improving the traceability of technical decisions. As part of the risk review and risk assessment process, CS 465 introduces two prioritization methods to support decisions on the management, inspection, and maintenance of prestressed concrete bridges. The common objective of these methods is to translate a heterogeneous set of technical, construction, and inspection data into synthetic risk indicators that establish a hierarchy of urgency among structures, structural elements, or critical points within an infrastructure network. The presence of two distinct approaches reflects the legislation's desire to provide complementary tools that can be used at different levels of detail and at various stages of the decision-making process. The first approach is called risk rating, and it is conceived as a global indicator that integrates factors related to the structural type, age of construction, construction details, and the structure's operational context. The other approach, called mean hazard risk level scoring, focuses more on inspection results and the identification of specific hazards, emphasizing the severity and probability of the observed degradation mechanisms. Although both methods aim to prioritize interventions, they use different approaches and can yield significantly different results depending on the risk profile considered. A clear understanding of the operating principles, assumptions, and parameters that influence the outcome is therefore essential for using the tools proposed by CS 465. The risk rating method provides a summary assessment of the risk associated with a post-tensioned concrete bridge by aggregating predefined factors that represent aspects relevant to the structure's safety and durability. These factors include the year of construction, the structural type, the post-tensioning system used, the presence of vulnerable construction details, and environmental and exposure conditions. The risk rating, expressed as a percentage, can be determined through Eq. 1. = 100((4 + + + ) )−6 254 (1) where is the construction year factor, is the form factor, is the vulnerable details and materials factor, is the condition factor, and is the consequence factor. Among these, the year of construction of the infrastructure is particularly significant, as it is one of the most influential parameters in calculating the overall score. This choice reflects the assumption that more recently constructed bridges benefit from both the evolution of post-tensioning technologies, which are now more mature and reliable than those used in the past, and from a lower degree of material and cable protection system aging. In addition to the year of construction, the risk rating considers factors related to the structure's characteristics and context. In particular, the structural form factor is introduced to characterize the bridge's overall structural strength and its ability to redistribute loads in the event of local damage. The presence of vulnerable details is considered to capture those construction aspects of the post-tensioning systems which, due to their design or execution methods, are more susceptible to degradation. The other factors concern the condition of the materials, the environmental and operating conditions, and the consequences associated with a potential collapse or loss of functionality of the structure. It is important to note that some key factors in the risk rating, in particular the year of construction and the form factor, are independent of the bridge's current condition. They are assigned based on design and construction information and reflect intrinsic characteristics of the structure that are not directly influenced by inspection results. Other factors, on the other hand, are directly linked to the bridge's condition and its post-tensioning system. The , and factors are assigned a discrete score, determined on the basis of predefined classes, while the score of the and are identified from 1 up to a maximum of 10 depending on the number of hazards identified. 2.1. Risk rating approach