PSI - Issue 84

Alessandro Scala et al. / Procedia Structural Integrity 84 (2026) 497–504

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extreme meteorological conditions in exacerbating damage severity and reducing the likelihood that distress remains confined to serviceability or partial failure levels. Overall, the results indicate that extreme events do not substantially alter the relative behaviour of different structural typologies but act as a dominant external forcing that amplifies damage severity across all bridge types. This finding underscores the importance of explicitly accounting for extreme events within infrastructure surveillance and management strategies, as their occurrence may significantly reduce the effectiveness of structural redundancy or favourable load redistribution mechanisms that can otherwise limit collapse under non-extreme conditions. 3.2. Extreme events and bridge materials A similar analysis was conducted with reference to construction material, focusing on masonry and concrete bridges, which represent the most prevalent categories in the database. The concrete group includes plain, reinforced, prestressed, and post-tensioned structures. As for structural typology, the sample size varies depending on the occurrence of extreme weather events. Under ordinary conditions, the dataset comprises 79 bridges, including 25 masonry and 54 concrete structures, whereas in the presence of extreme events the sample is reduced to 29 cases, with 10 masonry and 19 concrete bridges (Fig. 6).

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b)

Fig. 6. (a) Distribution of damage levels (DL1, DL2, DL3) for masonry bridges and reinforced concrete bridges in absence of extreme events; (b) Same classification for failures occurred during an extreme event.

Under ordinary conditions (Fig. 6a), all three damage levels are observed for both material categories. For masonry bridges, partial collapses (DL2) represent the most frequent damage level, accounting for nearly 50% of the cases, while minor distress (DL1) and total collapses (DL3) are less common. For concrete bridges, DL2 and DL3 occur with comparable frequencies, each accounting for approximately 40% of the cases, indicating a generally higher propensity toward severe damage even in the absence of extreme meteorological forcing. The dataset associated with extreme weather events (Fig. 6b) confirms and further amplifies the trends observed for structural typology. For both materials, the proportion of DL1 cases decreases markedly and completely disappears for concrete bridges. At the same time, the percentage of total collapses (DL3) increases significantly, reaching approximately 50% for both masonry and concrete structures. This shift highlights the strong influence of extreme events in driving damage toward the most severe collapse category, regardless of construction material. Overall, these results reinforce the findings obtained from the analysis by structural type and further emphasize the role of extreme events in increasing the likelihood of complete structural collapse. From an infrastructure management perspective, the material-dependent response observed under ordinary conditions tends to converge under extreme events, suggesting that the intensity and rapidity of such phenomena may override differences in material behaviour. This has important implications for monitoring strategies, inspection effectiveness, and post-event intervention planning, particularly in contexts where extreme meteorological conditions are expected to become more frequent.