This is the third installment of a series of articles examining how the building industry and building owners are addressing future effects of climate change. Click here for the first article, which examined responses to sea-level rise, and click here for the second article on preparing for storm surges.
Tornado disasters such as those that hit Tuscaloosa, Ala., Moore, Okla., and Joplin, Miss., grabbed media attention and sparked debates over the increased frequency of this powerful storms. But the issue at hand may be increased development, rather that rising tornado frequency. Larger and denser populations are beginning to cover once-open fields and, according to Dr. David O. Prevatt, assistant professor in the Department of Civil and Coastal Engineering at the University of Florida, new cities aren’t designed to withstand tornado forces. “There has been little innovation in designing for tornado wind loads,” Prevatt says. “We need a combination of solutions to this complex problem that includes financial support for ongoing research to quantify simultaneous loads on the roof and walls; entrepreneurship in building design; and the political will to improve the code even it that raises housing prices.”
Because billions of dollars in tornado disaster relief funds are spread across the national population, the effect seems much smaller. “So when media interest dies out, no new decisions have been made to support research or improve codes and these communities aren’t resilient. It’s a tremendous challenge,” Prevatt says.
Tom Smith, AIA, president of TLSmith Consulting in Rockton, Ill., is a member of American Society of Civil Engineers’ ASCE 7 Task Committee on Wind Loads and was lead author for the FEMA 2011 Recovery Advisory on design guidance for critical facilities in tornado-prone regions. Smith notes that weaker tornadoes generate wind speeds generally close to those of hurricane forces. “If we draw from improved hurricane-resistant designs and products, buildings in tornado alley could better withstand lower-speed tornadoes,” he says.
Smith is a strong advocate of occupant protection and says designing a walk-in closet as a bunker is fairly economical–between $6,000 and $10,000. He also believes that emergency facilities must be designed to protect equipment so that emergency response operations remain uninterrupted. The 2015 edition of the International Building Code will require that first-responder facilities and schools with 50 or more occupants in tornado-prone region of the country be designed for occupant protection. “Although the adopting jurisdictions may still choose to delete the provisions, I think this code change is an important first step,” Smith says.
Smith is also working on the 2016 edition of ASCE 7, which includes a commentary intended to guide professionals if clients want to voluntarily increase the tornado resistance of their buildings.
The cost of increasing building resistance is a significant factor and while more research is needed, Prevatt says that using the interior walls to tie the roof firmly to the foundation and to brace the exterior walls is a potential source of increased resistance. “We are now engineering houses with green building concepts and stronger insulation," he says. "If we take this opportunity to create a house that utilizes more of the structure as a structural element, people will be better able to absorb the price.”
Earlier this summer, our sister publication, BUILDER, ran an extensive series on tornadoes and building practices. Click on the links below for more details: