Tornado Loads on Building and Structures: Development of Tornado Hazard Maps and Load Provisions for ASCE 7-22
Research Engineer, Structures Group
National Institute of Standards and Technology
Marc Levitan is the Lead Research Engineer for the National Windstorm Impact Reduction Program at the National Institute of Standards and Technology. He has over 25 years in research on tornado, hurricane, and extreme wind effects on buildings and structures. With respect to tornado research, Dr. Levitan served as lead investigator for NIST's National Construction Safety Team technical investigation of the Joplin tornado, as well as for the NIST study of the 2013 Moore tornado. Dr. Levitan also leads implementation of many recommendations resulting from these investigations, including chairing: the SEI committee developing tornado load provisions for ASCE 7-22; the ICC committee that developed the 2020 edition of the ICC 500 Storm Shelter standard; and the ASCE/SEI/AMS committee developing a new standard on Wind Speed Estimation in Tornadoes.
This presentation provided an overview of the development of tornado load provisions proposed for incorporation into ASCE 7-22. These provisions are based on the wind load framework provided in ASCE 7-16 for other types of windstorms with modifications for tornadoes. Design speeds are defined using the first-ever engineering-derived probabilistic tornado wind speed maps, which also account for the dependency of tornado risk on the plan size of the building or structure. Unique tornado characteristic such as the bullnose-shaped vertical velocity profile, strong updrafts, and atmospheric pressure change are also accounted for. These tornado load proposals are currently working their way through the standards approval process for inclusion in ASCE 7-22.
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