With the recent violent weather outbreak this weekend causing more tornado deaths in one weekend than the yearlong 2016 total, I am once again raising the issue of better building in tornado zones. First published in 2013, the Dual-Objective-Based Tornado Design Philosophy, defies traditional assertions that there is nothing you can affordably build to withstand tornadoes. Those rebuilding in the aftermath of the devastating storms have affordable options to protect their homes and families from future events.
This revolutionary engineering design concept emerged after Tuscaloosa, Joplin, and Moore tornado investigations. Adding $1 per square foot to the cost of construction to improve structural performance for property protection and incorporating tornado safe rooms for essential life safety can alter the pattern of death and destruction we continue to suffer. This weekend’s tragedy is more evidence that it is time to embrace a better way of building.
As noted in our paper, “Building Codes: The Foundation for Resilience” the American Society of Civil Engineers (ASCE), Federal Emergency Management Agency (FEMA) Building Science engineers, and leading academic researchers have called for a way of building to meet the challenge of saving lives while also preserving property in the face of tornado outbreaks.
The research-informed effort comes in response to field investigations that documented a pattern of disproportionate structure collapse in tornado outbreaks. They point out how even small design changes can make a difference, and they have developed guidelines to estimate the tornado-induced loads. This will provide reasonable targets for designers to use in their future work. Homes built to these newer, research-informed guidelines will have the advantage of better wall bracing, improved roof tie-downs, and overall stronger connections.
According to the newly released January 21-22 Southeastern U.S. Tornado Outbreak Report, published by the Wind Hazard Damage Assessment Group (WHDAG) of the University of Florida, the widespread catastrophic failures are not of themselves failures of engineering, but they are the inevitable result of policies that ignore tornado loads from minimum building design standards. It will be up to the populations in our communities (neighborhoods, towns, states) to decide whether to follow the lead of Moore, OK and implement tornado-resilient building codes in the future.
Dr. David O. Prevatt, Associate Professor of the University of Florida, Department of Civil and Coastal Engineering states, “If we can put a man on the moon, we can keep a roof on a house, and our research demonstrates it is possible to design and build houses that protect people and structures from deadly winds. Techniques developed and implemented in Florida that have reduced hurricane losses can be applied and used in houses to also reduce tornado losses.”
This approach is buoyed by the finding by the National Climatic Data Center (NCDC) that 95 percent of tornado damage occurs at EF-3 and below. Accordingly, the Dual-Objective-Based Tornado Design Philosophy enhanced practices can bring material increases in home strength. Moreover, since 90 percent of all tornadoes never exceed EF-2 with winds of up to 135 mph, wind-resistant building practices can dramatically improve building performance in nearly every tornado event.
This is possibly one of the most important breakthroughs in high-wind design during the past two decades, as it offers an affordable innovation that can potentially improve life safety and economic well-being for millions of residents throughout the U.S.
Homes are a long-term investment. Eighty percent of our homes are more than 20 years old, and most of them will be around for at least another 30 years. Therefore, it’s important not only for individual families to make careful choices now as they rebuild, but each community must acknowledge its responsibility to rebuild in a resilient way.