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An engineering firm hired by attorneys for victims of the Interstate 35W bridge collapse says the cause of the disaster was not undersized gusset plates but the failure of a nearby beam, a lawyer for the victims said Wednesday. The firm's findings directly contradict the conclusion reached by the National Transportation Safety Board.
Chris Messerly, lead attorney representing 117 survivors and relatives of victims, said the engineering firm Thornton Tomasetti Inc. concluded that the beam was under immense stress partly because of the hot weather and the loads placed on the bridge's deck the day of its collapse. The firm said the bridge's bearings -- designed to allow for expansion and contraction -- were corroded, no longer moved and kept the bridge from expanding in the summer heat, causing the beam to fail.
Messerly is one of a group of attorneys gearing up for legal action against URS Corp., a consulting firm hired by the Minnesota Department of Transportation to evaluate the bridge, and Progressive Contractors Inc. (PCI), the company that had put hundreds of tons of construction materials on the bridge.
He called the collapse "a completely unnecessary event."
The bearings were "a maintenance issue that the state deferred to URS," said Messerly.
URS declined to comment Wednesday. Terry Williams, a spokesman for the NTSB, said the board stands by its report and declined to comment further. In its final report, released in November, the NTSB said the main cause of the collapse was the fact that gusset plates holding the bridge together were half as thick as they should have been.
Kyle Hart, a lawyer who is representing PCI in lawsuits that already have been filed, expressed skepticism about the findings and said he and his client have been working with Raths, Raths & Johnson, a structural engineering firm based in Chicago.
"There's simply no way that those gusset plates didn't play an instrumental role in the failure," he said.
A group of four bridge survivors has already sued PCI and URS, while Messerly said his group will file in the coming months, and certainly before Aug. 1, the two-year anniversary of the collapse. The bridge's designer, Sverdrup & Parcel, can't be sued because the firm has dissolved and the statute of limitations on design errors has run out.
The state owned the bridge, and anyone who accepts money from the $36.4 million victims compensation fund gives up the right to sue the state. Survivors and relatives have until April 16 to accept the state's offers, which were made last month.
Thirteen people were killed and 145 were injured when the bridge collapsed during the evening rush hour on Aug. 1, 2007.
Messerly said Thornton Tomasetti engineers "reached their conclusion after many, many months of computer analysis and modeling." He said they viewed the security camera video of the collapse and recently traveled to Maryland to examine key pieces of the bridge stored there.
Thornton Tomasetti presented its findings to survivors, families and lawyers on Tuesday evening in a conference center at the law firm of Robins Kaplan Miller & Ciresi, said Messerly, who is representing the clients at no charge. The presentation focused on a beam -- known as the L9-11 chord -- on the lower part of the steel trusses that supported the bridge. That chord was not directly connected to gusset plate U10 above it, but three other beams connected it to the bent plate.
In a fracture critical bridge such as the 35W bridge, the failure of one member can bring the whole structure down.
"One thing that so saddened the victims here and upset them was that this was a completely unnecessary event," Messerly said, calling for a wider look at bridge bearings around the country.
In its report, released in November, the NTSB said it found "roller wear marks" indicating that the bearings did have some movement, though it also described the movement of the bearings on some piers as "insufficient." A report by Wiss Janney Elstner Associates Inc., a firm that was hired by the state and worked with the NTSB, indicated that the bearings' lack of movement actually served to strengthen the bridge at the time of the collapse.
With offices around the world, Thornton Tomasetti has worked on projects ranging from the world's tallest buildings to the new Minneapolis Central Library. On the forensic side, the firm says it investigated the deadly collapse of a crane during the construction of Milwaukee's Miller Park baseball stadium and was on the task force that determined the "mode of failure" of the World Trade Center towers in 2001.
Jim Foti • 612-673-4491