Marc Levitan, Long Phan and the Tornado Wind Loads Team

Tornadoes kill more people per year in the U.S. than hurricanes and earthquakes combined. However, for years, American building codes lacked requirements for tornado-resistant design and construction, leading to unnecessary property damage and fatalities.   

Today those codes exist, thanks to Long Phan and Marc Levitan, two structural engineers at the National Institute of Standards and Technology who led a decade-long effort to create the world’s first tornado design standards. These historic standards will enable builders to construct the nation’s critical facilities, including hospitals and schools, to withstand 97% of the roughly 1,200 tornadoes that occur in the U.S. each year.    

“This work will save a lot of lives. People used to say, ‘what can you do about tornadoes? We’ll just have to live with people dying.’ Marc and Long have shown that we don’t have to,” said Joannie Chin, director of NIST’s Engineering Laboratory.  

Challenging assumptions about tornadoes  

According to Phan, builders and engineers have long viewed tornadoes as “an act of God”—too severe, too random and too expensive to design for. That’s because the original Fujita Scale, used by scientists to measure tornado strength until 2007, often overestimated tornadic wind speed by not factoring building quality and design into how much damage tornadoes cause on the ground.    

A turning point came in 2011 when Phan and Levitan led NIST’s investigation into a deadly EF5 tornado in Joplin, Missouri. During the investigation, they observed that the tornado had left intact an entire floor of a completely damaged building in a hospital complex, thanks to its impact-resistant exterior. This suggested that buildings could be designed to resist tornadoes, and the team’s final report recommended NIST create national standards to that effect. 

To do so, the team analyzed more than 60 years of National Weather Service records to examine where and how often tornadoes occur and how they affect buildings. They also conducted wind tunnel experiments to determine how miniature buildings responded to small-scale vortexes, verifying their results with real-world data.   

Combined with economic analyses, these findings proved that designing for EF0-EF2 tornadoes would protect people from most of the tornadoes in the U.S.—and that builders would not have to break the bank to meet new design standards.   

“They translated important research into practical engineering terms that the average practitioner could use to design and build safer buildings,” said Dominic Sims, CEO of the International Code Council.  

Changing the building code   

Levitan said that he and Phan performed “educational work and outreach” to introduce the new standard into the building code, hosting workshops and meetings to painstakingly advance proposals through the American Society of Civil Engineers, which publishes the definitive guide for engineers to calculate design loads for buildings and other structures.    

Following a lengthy consensus process, the society approved the new tornado wind load standard in 2021. A committee in charge of updating the International Building Code, which prescribes baseline safety standards for most buildings in the U.S., excluding houses, adopted the new regulation unanimously for 2024.   

“Marc and Long got the building code community to yes when, for over 100 years, they had been at no,” said Jason Averill, deputy director of NIST’s Engineering Laboratory.   

The new codes will apply to all new critical facilities, such as schools, hospitals, emergency centers and nursing homes, as well as high-occupancy buildings like theaters. The team is now working to extend the codes into single-family housing.   

Phan began working at NIST in 1984 while Levitan joined in 2011. Both hold doctorates in civil engineering and take pride in applying their expertise to public service.     

“We enjoy seeing our research go into practice to make a difference,” Levitan said.   

“Government work is like a super university where your research has a bigger purpose. I am proud to work on things that help improve public safety,” Phan said.