Even as the pressure to demand safe rooms in a wide range of buildings fizzled out, engineers were working on an even bigger goal: to change the way buildings are designed and constructed in tornado zones, to survive them all. storms, except the most violent.
Designing a structure to withstand tornado winds involves two basic steps, according to Don Scott, who helped develop tornado-resistant building standards at the American Society of Civil Engineers. First, the roof should be securely attached to the walls, and the walls to the foundation, in order to transfer the pressure from the tornado to the strongest part of the building.
Second, windows and other openings must be strong enough to survive debris, such as tree branches, that are thrown through the air at high speed during a tornado. If a window shatters, the wind pressure from the tornado is forced into the building, “like blowing up a balloon,” Scott said. Covering windows with a special varnish can keep them from shattering, like hurricane-resistant windows in Florida, he said.
Scott and his colleagues at the civil engineering firm set out to turn the findings of the National Institute of Standards and Technology’s Joplin report into building requirements for inclusion in the next version of the model building code in 2024.
Here, too, the construction industry has succeeded in reducing these targets.
Stricter design standards and impact resistant windows work for any type of structure, Scott said. But as the engineering firm began work, Mr Scott said he received a warning from Gary Ehrlich, head of standards at the National Association of Home Builders: whether Mr Scott’s group recommended applying those standards to houses, the recommendations would never be in the model codes.
Ms Thompson, the spokesperson for the homebuilders group, declined to make Mr Ehrlich available for comment.