A design flaw may have led to the fatal collapse of a pedestrian bridge during construction at Wake Tech’s Northern Campus in November, the state Department of Labor found.
The collapse on Nov. 13 killed one worker and hurt four others. A second, similar bridge collapsed without injuries.
The collapses were caused by “design flaws” associated with notches in the bridge’s supporting girders, according to Labor Department spokesman Neal O’Briant. The girders were made of glulam, an engineered wood product that can be bent into curved shapes.
The Labor Department’s Occupational Safety & Health Division concluded that Stewart Engineering Inc. should have spotted a flaw in the design as it prepared drawings of the structure, O’Briant said. But the department won’t fine or sanction the company because it doesn’t regulate engineering.
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“There aren’t any regulations that cover the design of the bridge itself,” said Jay Wilkerson, a law partner with Conner Gwyn Schenck who is not involved with the case and was commenting generally. “That’s just a matter of professional responsibility.”
But some of the engineers involved could face fines, or lose their licenses, in a subsequent investigation by a state licensing board for engineers. Victims and families of victims of the collapse also may file civil lawsuits for injury and wrongful death.
Workers were pouring concrete for the bridge when a 140-foot section plunged into a ravine on the morning of Nov. 13. The fall was as much as 40 feet in places, emergency officials said that day.
A second partially completed bridge fell that night. Skanska had suspended work on that span after the first collapse, and no one was injured when it fell.
The Occupational Safety & Health Division found that “engineering design deficiencies contributed to the collapse of both pedestrian bridges.”
The division sent its conclusion to Stewart Engineering, the firm that prepared shop drawings for the bridge-builders to follow; to Skanska USA Buildings, the general contractor; and to J.O. Concrete Services Inc., whose workers were putting up the first bridge when it fell.
The Engineered Wood Association, an industry group, calls glulam “a highly innovative construction material” that pound for pound is stronger than steel.
The material consists of wood layers laminated together with a heavy-duty bonding agent. The collapse of a skating rink in Germany, which killed 15 people in 2006, was reported to have involved a glulam support that compressed when it was exposed to moisture, the New Civil Engineer reported.
Stewart Engineering released a written statement on the collapse late Friday morning.
“Stewart cooperated fully with the OSHA investigation and is committed to continue in that regard with other investigations,” company representative Mary Heath said. “Because of ongoing investigations, it is not appropriate for us to discuss this matter publicly at this time. We continue to assist and work earnestly with all the involved parties to move the process forward.”
The state Board of Examiners for Engineers and Surveyors is in the earliest stages of its own inquiry into the collapses, according to Andrew Ritter, the group’s executive director.
The board is empowered by the state both to grant licenses for engineers and to discipline them for their failings. The board received notice of the state’s general findings last week, Ritter said.
Now its investigators will determine what penalties, if any, might be appropriate in this case.
“In a complex case, we are trying to get every piece of paper that’s involved in this project, perhaps 500 to 1,000 pages, and talking to everyone involved, primarily in the engineering aspect,” he said.
Multiple engineers might be the subject of the investigation, he said. The board’s maximum punishments are a $5,000 fine and the revocation of an engineer’s license.