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NTSB finds design flaw caused Minneapolis bridge collapse

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FREDERIC J. FROMMER
January 15, 2008
— Federal investigators have identified a design flaw as the cause of last year’s Interstate 35W Minneapolis bridge collapse that killed 13 people and injured about 100, a congressional official said Tuesday.

The official, who was briefed by the National Transportation Safety Board, said that investigators found a design flaw in the bridge’s gusset plates, which are the steel plates that tie steel beams together. The official spoke on the condition of anonymity so as not to pre-empt an update being provided later Tuesday by the NTSB chairman, Mark V. Rosenker.


The findings are consistent with what the NTSB said about a week after the Aug. 1 collapse, in which the bridge plunged into the Mississippi River. At the time, the NTSB said it had found issues with the collapsed bridge’s gusset plates, but expected a full investigation to take more than a year.


Meanwhile, Transportation Secretary Mary Peters is expected to issue an advisory later Tuesday urging states to check the gusset plates when modifications are made to a bridge – such as changes to the weight of the bridge or adding a guardrail, said a federal official with knowledge of the plans. The official spoke on condition of anonymity because Peters had not yet made the announcement.


Currently, such calculations are done for the entire bridge, but not down to the gusset plates, the official said.


Last August, Peters advised states to consider the additional stress placed on bridges during construction projects. An 18-person crew was working on the bridge when it collapsed.


Nearly three months later, she told a gathering in Washington of a “working theory” of a poorly designed gusset plate and a heavy load of construction materials.


Meanwhile, state lawmakers announced plans last month to spend up to $500,000 to hire legal counsel to aid in a legislative inquiry into the collapse.


The bridge was deemed “structurally deficient” by the federal government as far back as 1990.


Late last year, President Bush signed a massive spending bill which included $195 million to help replace the bridge. That came on top of the $178.5 million the federal government has already given Minnesota for the project.



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