PSI - Issue 84

Alessandro Lipari et al. / Procedia Structural Integrity 84 (2026) 615–622

622

framework of the recent Italian guidelines on existing highway bridges. In particular, the proposed approach is most useful for the verification at the so-called operational conditions, in which reduced partial safety factors are used. Extreme value theory is suitable to analyse variable actions, such as the traffic loading, and derive site-specific characteristic traffic loading values for structural verifications. It is recommended using the GEV distribution, which encompasses the traditionally used Gumbel distribution. A sample 50-m-long bridge is presented as a case study. The midspan bending moments are computed by applying traffic microsimulation based on traffic recorded on a motorway in Poland and are compared to the Eurocode Load Model 1, as well as to the additional models in the Italian guidelines. In spite of conservative assumptions made on the congestion occurrences, the case study shows that the use of site-specific traffic data leads to considerable reductions in load effects, while keeping the safety levels required. This approach may spare many existing bridges from unnecessary restrictions or interventions. Acknowledgements This study was carried out within the RETURN Extended Partnership funded by the European Union Next GenerationEU (National Recovery and Resilience Plan—NRRP, Mission 4, Component 2, Investment 1.3—D.D. 1243 2/8/2022, PE0000005). The author is also grateful to Dr Paolo Clemente for his valuable advice. References Bruls, A., Calgaro, J.-A., Mathieu, H., Prat, M., ENV 1991 - Part 3 : The main models of traffic loads on road bridges - Background studies. IABSE Colloquium, Delft, 1996. 215-228. Caprani, C. C., Enright, B., Carey, C., 2012. 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