Design Flaw Blamed For Minnesota Bridge Collapse

November 15, 2008 7:00 p.m. EST

Washington, DC (AHN) - A design flaw was likely to blame for the Aug. 2007 collapse of an eight-lane bridge in Minneapolis, Minn., federal investigators say.

The National Transportation Safety Board reported Nov. 14 that the probable cause of the collapse of the I-35 bridge was "inadequate load capacity" due to a design error by the engineering firm Svedrup & Parcel and Associates.

The NTSB also blamed state and federal officials for not catching the errors when reviewing the plans.

Investigators say devices meant to hold connections together, known as gusset plates, buckled under pressure from heavy traffic, causing a large portion of the 1,907-foot long highway bridge to collapse into the Mississippi River.

One thousand feet of the bridge deck truss collapsed, with about 456 feet of the main span falling 108 feet into the 15-foot deep river.

Thirteen people died in the accident and 145 were injured. A total of 111 vehicles dropped into the water, and 17 were recovered.

"Bridge designers, builders, owners, and inspectors will never look at gusset plates quite the same again, and as a result, these critical connections in a bridge will receive the attention they deserve in the design process, in future inspections, and when bridge load ratings analyses are performed," NTSB Acting Chairman Mark Rosenker said in a statement.