Carew Tower couldn't tolerate similar strike
Should a terrorist ever strike a prominent local landmark such as the Carew Tower with a fuel-laden 767, Cincinnati's tallest building wouldn't do much better than the World Trade Center, said local experts in structural engineering.
Elmer Obermeyer is president and chairman of Graham Obermeyer & Partners Ltd., a structural engineering firm in downtown Cincinnati. After 45 years in the business, the University of Cincinnati graduate is considered the guru in his field in the Tri-State, according to several local builders and construction professionals.
Obermeyer's firm has frequently done tenant build-out work in the 49-story tower at Fifth and Vine streets that has defined the city skyline for several generations. He said the building is solid, constructed of concrete and steel, but it's not invulnerable.
"We've checked on their framing and everything's fine, but it wouldn't stand a chance," Obermeyer said.
Obermeyer has been called on before in times of tragedy: He was hired to perform an analysis of the 1981 collapse of suspended walkways at the Hyatt Regency Hotel in Kansas City, Mo., a tragedy that claimed 114 lives and injured more than 200 people.
Obermeyer said nothing like the Kansas City debacle is likely to happen here, but he added that buildings in Greater Cincinnati adhere to a code that's uniform across the United States.
"In general, I don't think there's any basic difference. A lot of our buildings, particularly the older ones, have concrete frames, and while most of the newer ones are steel-frame, theoretically they both have to have the same fire resistance and strength for wind and earthquakes, that type of thing," Obermeyer said.
"With the newer codes, it's not spelled out real specifically, but they generally want some redundancy in design to protect against a progressive collapse. They don't want buildings going down like a stack of cards when you pull one out," he said. "They are designed to protect themselves, so if one column is knocked out and destroyed, the whole building won't come down."
Charles Nutt, senior structural engineer at Tectonic Engineering Consultants in West Chester, is in charge of that company's portfolio of Tri-State projects that includes office buildings, cell phone towers, foundations and retaining walls.
Nutt said even though many of downtown Cincinnati's buildings are made of reinforced concrete, what can't be written into a building code is how to build a facility that would withstand the kind of fireball that hit two of the tallest buildings in the world, each stretching 110 stories into the sky.
"From what I could tell, the building withstood the initial impact, but it wiped out so much inside the building the floors above started coming down," Nutt said. "That same thing would happen here, if the buildings actually behave as they're designed, which is to implode so they don't topple into the next one."
Obermeyer said the fire probably melted the steel beams of the World Trade Center towers, which were never designed to survive the kind of shot they took Sept. 11.
"Probably the most stringent building code requirement requires three hours of fire resistance, but they're talking about the contents of a building burning and that sort of thing, not 10,000 pounds of flaming aircraft fuel thrown in there," Obermeyer said. "A concrete building probably has a little more resistance than the steel ones, which most of the new ones are made from, but there's nothing anybody could do with that kind of impact. Nothing's ever been made to withstand that. Nothing ever will be."