Officials offered faulty bolt connections as the leading cause of the Feb. 5 collapse of a steel beam that sent a second-floor loading dock at the David L. Lawrence Convention Center crashing into the street.
The same kind of connection caused another beam to fall in 2005, something that wasn't disclosed until Wednesday. At least one expert said the type of connection used was "unreliable."
Bolts jammed in a sliding connection that is designed to let the building contract in a cold spell, causing the collapse two weeks ago that will cost the city-county Sports & Exhibition Authority more than $1 million to repair, officials said.
They're hoping to reopen the building in time for the Duquesne Light Pittsburgh Home & Garden Show, set for March 9-18.
Experts still can't say why the bolts failed to slide properly. A New York metallurgy firm, Lucius Pitkin, is trying to determine that. The company's spokesman, Robert Vecchio, refused to comment.
The failed connection and 25 others like it will be replaced with a shelf-like support covered with Teflon.
It wasn't the first time this type of connection has failed since the $370 million center opened in 2003, sports authority Executive Director Mary Conturo said. Another failure in February 2005 was not disclosed, she said.
"With hindsight, we probably should have had an independent review at the time done. But we thought we were getting a satisfactory response in terms of what needed to be addressed," said Conturo, who became executive director in 2004.
An angry county Chief Executive Dan Onorato said an internal investigation would determine why he wasn't told of that incident -- in which a steel beam, located 60 feet from the one that recently collapsed, fell 2 1/2 inches before being stopped by a column, engineers said.
It was fixed with the same shelf-type supports called for now.
Onorato said he learned of the 2005 collapse about seven days ago. "I didn't know it happened. I'm not happy about it."
Current sports authority board members weren't told until minutes before yesterday's briefing by Conturo, said board member Wayne Fontana, a Democratic state senator from Brookline.
"Obviously, it's disappointing to not have known about it and find out about it (Wednesday)," Fontana said.
One expert in analyzing building failures said the connection that failed -- a metal piece with slotted holes that allow bolts to slide -- was structurally "unreliable."
"I've never talked to a structural engineer that thought this was a reliable way to do an expansion joint," said Gregory Luth, whose Santa Clara, Calif., firm designed a casino and racetrack outside Harrisburg and a Disneyland hotel.
Luth was not involved in the inspection at the convention center, but reviewed diagrams of the connection provided by engineers.
"In my opinion, this would not be first-class engineering," he said.
Luth, who also designed One Oxford Centre, Downtown, has experience analyzing what causes buildings to fail.
"I've only seen the slotted hole connection used one other place in an expansion joint in 30 years of doing engineering. And it fell in that place, as well," Luth said. That was at a Hyatt Regency hotel in Kansas City, in 1979.
The sports authority hired Cleveland-based Wiss, Janney, Elstner Associates, and Leslie E. Robertson Associates, of New York, to conduct an independent review of the collapse.
Also, engineer Gary Panariello with the firm Thornton Tomasetti was hired by the contractor that built the center and its architect to determine the cause.
"I would say the fact that (the connection) failed means it was a poor choice, but at the time it probably seemed like a reasonable choice. Certainly, I wouldn't expect any of the parties here to use the same connections in a similar fashion in the future," said Andrew Osborn, the sports authority's main inspector.
The beam fell onto part of 10th Street and pedestrian walkways, bringing down a 30-by-60-foot concrete slab from a second-floor loading dock. No one was injured. A tractor-trailer became stuck in the collapsed area, and a cherry picker fell onto the sidewalk below.
It was the third failure of a steel connection at the convention center.
Iron worker Paul Corsi, of Moon, died in February 2002 when workers used incorrect nuts to connect pieces of steel during the building's construction. A truss fell and crushed Corsi.
Conturo said the 2005 incident was caused by bolts that were too tight.
Onorato said the investigation will continue until he knows who "is responsible for what happened."
"I am not going to allow this to just be passed off onto an iron worker, because we have a lot of inspections that were involved and a lot of design work involved," he said.
County Council plans to question Conturo and sports authority board members March 6 during a public meeting about the building's safety, said council President Rich Fitzgerald. The 2005 incident will be included in questions.
"Obviously, the mayor and chief executive, at the very least, should have been notified," Fitzgerald said.
Fitzgerald said he wants a signed guarantee from an independent engineering firm that the building is safe.
Engineers said the collapse was not related to a 2001 foundation shift that damaged caissons. The worst shifting was on the Allegheny River side of the building, while the collapse occurred on the Downtown side of the building.
Insurance policies will cover costs, Conturo said, including $350,000 for the new connections, $329,000 for collapse repairs and $85,000 for removing debris.
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