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Professor Studying Recent Oklahoma Tornado Destruction to Recommend Better Building Practices

Friday, June 07, 2013
Male stands against van in red hard hat
Storm Aftermath: Mechanical Engineering Professor Fred Haan, who specializes in study storm damage to woodframe buildings caused by tornadoes and hurricanes, was a member of a national team that examined the aftermath of recent storm damage in Moore, Oklahoma.

Mechanical Engineering Professor Fred Haan, PhD, is studying the destruction of structures in the path of this spring's tornado in Moore, Oklahoma, to influence building practices to better withstand future storms.

Haan was among a team of structural engineers and researchers that traveled to Oklahoma at the end of May as part of the National Science Foundation Rapid Response Grant for Exploratory Research. He helped investigate and gather data about the damage to, and performance of, woodframe structures in the affected areas due to strong winds.

Several schools and several thousand residential homes were damaged or destroyed, and the performance of these structures provided an important research opportunity to document any advancement in building practice of wood-frame homes in tornado-prone areas.

"A neighborhood is only as strong as its weakest house," says Haan, who has studied the effects of winds on structures for more than 20 years. "We're trying to make stronger structures that could be constructed now and in the future to prevent such widespread destruction and high replacement costs."

Haan strives to better understand the forces generated by large tornadoes and the distribution of wind force across a tornado's path, as well as joining other engineers and scientists in making recommendations for design code improvements and general safety guidelines.

The professor believes it would not be cost effective to design homes that could withstand an EF5 tornado, like the one that hit Moore, but roofs would remain attached in 90 percent of other tornadoes with winds of 130 miles per hour or less-if builders used stronger connectors within the building's substructure.

"You can have stronger connections from the roof to the wall and from the wall to the foundation. These connections are relatively cheap to implement. They are pieces of steel that are stamped. They only cost about $1 a piece," Haan says.

The tornado that struck Moore traveled rather slowly, according to Haan, so it was able to grind away on the center of the damage path for a long time. As expected, most of the houses right in the center were completely destroyed. However, houses farther from the center showed some of the typical damage that Haan and his colleagues often see in wind storms-and could be improved with stronger building connections.

"Many people in the dead center of the storm probably only survived because they had storm shelters," states Haan. "Simple construction changes could make a big difference in preventing wide-range destruction. Keeping the structural integrity of a house greatly reduces the debris that can become a part of any tornado, and helps protect a family's belongings and a home's interior from the damage that results from rain and wind getting inside."

Haan has started analyzing data collected from the recent trip to Moore, and hopes to join colleagues in completing building code recommendations by the end of the summer. This plan may be shared with government officials and house construction firms in areas impacted by strong winds from tornadoes and hurricanes. He will also be presenting a research paper on tornadoes impact on structures later this month at the Americas Conference on Wind Engineering in Seattle.

Other members of the exploratory research team are professors from the University of Alabama, University of Florida, Mississippi State University, Oregon State University, and Oklahoma State University. Several team members also worked together in 2011 to study damage left in the wake of massive tornadoes in Tuscaloosa, Alabama, and Joplin, Missouri.