TornadosNew Building Standard Can Map Out Tornado Threat for the First Time
Of the natural hazards in Mother Nature’s arsenal, tornadoes are some of the most vicious. But while other hazards are regularly considered in building designs, tornadoes have not been part of the equation for most structures in the United States, even in highly tornado-prone regions. Now, an upcoming edition of a critical building standard gives tornadoes some much needed attention.
Of the natural hazards in Mother Nature’s arsenal, tornadoes are some of the most vicious. But while other hazards are regularly considered in building designs, tornadoes have not been part of the equation for most structures in the United States, even in highly tornado-prone regions. Now, an upcoming edition of a critical building standard gives tornadoes some much needed attention.
The American Society of Civil Engineers (ASCE) has released a draft version of the 2022 edition of ASCE 7 for public feedback ahead of its final publication in December. This building standard helps engineers determine the loads (or forces) their building should be able to withstand, whether from a hurricane, earthquake, flood or snow. With the new edition, tornadoes may soon join that list, thanks to research spearheaded by the National Institute of Standards and Technology (NIST).
The draft of the new edition features first-of-a-kind tornado hazard maps meant to guide the design of critical facilities, such as schools, fire stations and hospitals, based on their size and geographic location.
“If the standard is ultimately adopted into the building code, it will provide some much-needed basic protection against tornadoes, reducing damages and accelerating recovery especially in the central and southeastern U.S.,” said NIST research structural engineer Marc Levitan, who chairs the ASCE task committee that developed ASCE 7’s new tornado load chapter.
Tornadoes cause more deaths per year than earthquakes and hurricanes combined. And storms spawning tornadoes surpass the collective annual insured losses of hurricanes and tropical storms. But, barring tornado shelters and nuclear power plants, building designs have historically not accounted for tornadoes. The extraordinary strength of tornadoes and a common perception that the risk of being struck by one is low have fed into a misconception that addressing tornadoes in building designs would be far too costly.
That mindset started to shift in 2011, when a record-breaking tornado season wreaked havoc across the U.S. NIST thoroughly investigated one of the worst events that year, a tornado rated as the most severe on the Enhanced Fujita (EF) Scale — an EF5 — that ripped through Joplin, Missouri. Among the more than 8,000 buildings damaged in the tornado’s wake were schools, big-box stores, nursing homes, fire stations and a major hospital, which was eventually demolished.
