Extreme tornado events can cause damage and loss of life as a result of flying debris and collapsing structures. While most tornadoes are generally weak and occur in lightly populated areas, there are extreme events, like one in March 2020 that ravaged Tennessee. Multiple storm systems resulted in two tornadoes, one in Cookeville, Tennessee, and the second near Baxter, Tennessee with wind speeds of 175 mph. The structural failure, injuries and loss of life of these events raise questions as to how best to mitigate similar future conditions. Post-event observations suggest that modifications to certain common construction practices might significantly enhance resistance to extreme wind forces.
A new paper in the Practice Periodical on Structural Design and Construction, “Structural Observations and Tornado Damage Mitigation Concepts: March 2020 Tennessee Tornadoes”, by Craig Henderson; Tim Huff, M.ASCE; and Gary Bouton, discusses these observations and provides recommendations for improving structural strength and resiliency. Learn more in the abstract below, or by reading the full paper in the ASCE Library.
Early in the morning of March 3, 2020, a storm system producing multiple tornadoes passed through middle Tennessee. One of the tornadoes—touching down in Cookeville and Putnam County—was classified as an EF4 with winds of approximately 282 km/h (175 mph). Damage observations after the tornado in Cookeville suggest that modifications to certain common construction practices might significantly enhance resistance to extreme wind forces. This paper provides recommendations for improving strength and resiliency within residential structures, particularly in four critical areas: (1) stiffness and strength of gable trusses, (2) wall-to-floor connections, (3) sill plate anchorage, and (4) shear and tensile capacity at interior foundation piers. Though improvements to construction practices are unlikely to eliminate damage to residential structures, such measures may well mitigate damage and extend the time between onset of the extreme forces and final damage or collapse.
Read the full paper in the ASCE Library: https://doi.org/10.1061/(ASCE)SC.1943-5576.0000571