John Osteraas

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John Osteraas

John Osteraas, center, salvages materials from the collapsed World Trade Center buildings in the shadow of Manhattan. (32K JPG)

John Osteraas may not be a household name, but he's been at the center of one of the most important stories in recent times — the collapse of the World Trade Center buildings.

Osteraas, director of the civil engineering practice at California-based Exponent Failure Analysis, has been one of a handful of civil engineers who has extensively studied the collapse of the World Trade Center buildings up close. His work has proved critical in assessing exactly why the two towers collapsed after being struck by airplanes on Sept. 11, 2001.

Osteraas' research on the World Trade Centers is an outgrowth of his work with the Federal Emergency Management Agency's Urban Search and Rescue Team, established 10 years ago to respond to and investigate natural disasters such as earthquakes and hurricanes. The team was established in the wake of an earthquake in Mexico City, when haphazard rescue efforts led to deaths beyond those originally caused by the earthquake.

But Osteraas says the team's role has expanded in the wake of incidents such as the bombing of Murrah Federal Building in Oklahoma City in 1995. Beyond extracting victims trapped in structures, members of the team investigate building sites to determine how they collapsed, where victims might be found, and how rescue and clean-up efforts can go forth without endangering workers.

"It's a little bit like archeology and a little bit of investigative work and a little bit of engineering," he says. "Typically we never find all of the puzzle pieces. You have to infer with the best pieces available."

Osteraas was born in Wausau, but moved to Madison in the sixth grade. He enrolled at UW-Madison, and took a liking to engineering. He quickly found mentors in now-Emeritus Civil & Environmental Professors C.K. Wang and Chuck Salmon. To this day, Osteraas says, he applies lessons he learned from his classical methods of structural analysis course. "I attribute that class to my understanding of structural behavior," he says. "I see something and say, 'Aha, I remember that.'"

For Osteraas, the collapse of the World Trade Center towers represented an obvious challenge. Almost all of the buildings were destroyed in the collapse, resulting in the destruction of much of the evidence that engineers like Osteraas rely on to reconstruct collapses.

But debris from "Ground Zero," which Osteraas inspected, as well as sophisticated computer modeling, has allowed engineers to reconstruct the events that led to the buildings' collapse.

Although there is considerable ongoing debate about exactly how the towers collapsed, Osteraas says most engineers agree that the towers' floors began to sag due to the stress put on the buildings' support columns. Those columns, and the bolts used to attach them to the floors, were weakened by the impact of the airplanes and the incredibly hot temperatures from the resulting explosion.

Once one floor collapsed, the others were sure to follow, according to Osteraas' analysis, comparing the collapsing floors to a giant hammer going through the towers.

"It was far beyond anything ever anticipated or designed for," he says. "It was amazing they stood for as long as they did."

Despite the tragedy of the attack on the World Trade Center, and the subsequent collapse of its towers, Osteraas firmly believes that engineers can learn lessons from it about how to make buildings structurally more sound and safer.

"We don't learn much from our successes," he says. "The curse of engineering is that when it does its job, it's taken for granted. Our work is totally invisible."

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