Even as the push to require safe rooms across a wide range of buildings fizzled, engineers were working on an even more ambitious goal: Changing the way buildings are designed and constructed in tornado zones, to survive all but the most violent storms.
Designing a structure to withstand tornado winds involves two basic steps, according to Don Scott, who has helped develop tornado-resilient building standards at the American Society of Civil Engineers. First, the roof must be tightly secured to the walls, and the walls to the foundation, in order to transfer the pressure from the tornado downward to the strongest part of the building.
Second, windows and other openings have to be strong enough to survive the debris, like tree limbs, that gets hurled through the air at high speeds during a tornado. If a window breaks, the wind pressure from the tornado is forced into the building, “like blowing up a balloon,” Mr. Scott said. Covering windows with a special glaze can prevent them from being shattered, similar to hurricane-resistant windows in Florida, he said.
Mr. Scott and his colleagues at the civil engineering society set about turning the findings from the National Institute of Standards and Technology’s Joplin report into building requirements to be incorporated into the next version of the model building code in 2024.
Here too, the building industry succeeded at whittling down those aims.
Stronger design standards and impact-resistant windows work for any type of structure, Mr. Scott said. But as the engineering society began its work, Mr. Scott said he got a warning from Gary Ehrlich, the head of standards at the National Association of Home Builders: If Mr. Scott’s group recommended applying those standards to homes, the recommendations would never get into the model codes.
Ms. Thompson, the spokeswoman for the home builders’ group, declined to make Mr. Ehrlich available for comment.