Valutazione dell'impatto da carichi da tornado sui ponti

Catastrophic instances like the 2011 Joplin tornado in the United States have amplified concerns over tornado-induced damages worldwide. Europe, particularly Italy’s northeastern regions, have also witnessed significant tornado activity. Despite these threats, current structural design stand- ards, specifically the Eurocodes, fail to incorporate tornado load considerations in their verifica- tions at limit states. To address this gap, the study applies tornado loads to a steel-concrete bridge deck model, and evaluates its response to various tornado intensities classified by the Enhanced Fujita (EF) scale from EF0 to EF5. Results from the study reveal the need to revise current design standards to include tornado load considerations, thereby enhancing the resilience of civil infrastructure against the increasing threat of extreme weather events and ensuring the safety and structural integrity of bridges.

Casi catastrofici come il tornado Joplin del 2011 negli Stati Uniti hanno intensificato le preoccu- pazioni sui danni indotti dai tornado in tutto il mondo. Anche l’Europa, in particolare le regioni nord orientali dell’Italia, sono state testimoni di una significativa attività di tornado. Nonostante queste minacce, gli attuali standard di progettazione strutturale, in particolare gli Eurocodici, non incorporano considerazioni sui carichi dei tornado nelle loro verifiche agli stati limite. Per colmare questa lacuna, lo studio applica i carichi dei tornado a un modello di impalcato di ponte in acciaio-calcestruzzo e valuta la sua risposta a varie intensità di tornado classificate dalla scala Enhanced Fujita (EF) da EF0 a EF5. I risultati dello studio rivelano la necessità di rivedere gli attuali standard di progettazione per includere considerazioni sul carico dei tornado, migliorando così la resilienza delle infrastrutture civili contro la crescente minaccia di eventi meteorologici estremi e garantendo la sicurezza e l’integrità strutturale dei ponti.

Tornadoes, characterized by violently rotating and translating vortices formed from supercell thunderstorms, are among the most destructive natural hazards, capable of producing winds up to 135 m/s. These localized windstorms frequently cause immense economic damage and loss of life, with tornadoes being some of the most severe weather events

For instance, the Joplin tornado on May 22, 2011, was the deadliest and costliest single tornado in U.S. history, claiming 162 lives and causing approximately $ 2.8 billion in damage. From 2000 to 2020, an average of 1,225 tornado events and 74 tornado-related deaths occurred annually in the United States according to the National Oceanic and Atmospheric Administration in 2021.

While tornadoes are most frequent in the United States, they also occur in Europe. Notably, northern Italy has experienced significant tornado activity, such as the July 2015 event near Venice that resulted in one death and € 20 million in damages as reported by the Regional Environmental Protection Agency. This growing global awareness has spurred increased research interest in tornado impacts beyond the United States.

Tornado intensity is assessed using scales such as the Enhanced Fujita (EF) Scale, which rates tornadoes from EF0 (weak damage) to EF5 (almost complete destruction) based on their impact on vegetation, buildings, and vehicles. In northeast Italy, between 1905 and 2017, the most extreme tornado intensities have ranged from F3 to F5 according to the Fujita (F) Scale introduced in 1971 and based on damage investigation from F0 (light damage) to F6 or above (inconceivable damage). Statistical investigation of significant tornadoes shows the geographic distribution in Italy with 57 EF2+ tornado events recorded between 2000 and 2018 on the Fig. 1. Despite the evident threat, European design standards, particularly the Euro- codes, do not account for tornado loads in structural verifications at limit states. Ensuring the safety and climate resilience of structures against extreme weather requires incorporating tornado considerations into design standards. This study aims to assess the impact of tornado loads on a steel-concrete composite bridge deck at limit states.

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L'intera memoria è in lingua inglese.

La presente relazione è stata presentata in occasione del XXIX Congresso CTA, svoltosi a Milano il 26 e 27 settembre 2024.