Report: Design flaw likely caused bridge collapse

Congressman criticizes safety board

MINNEAPOLIS – The chairman of the House Transportation Committee criticized federal investigators Sunday after a published report said an original design flaw is the most likely reason for the collapse of the Interstate 35W bridge in Minneapolis.

National Transportation Safety Board investigators believe the bridge’s original designers probably neglected to calculate the size of key gusset plates – devices that help connect steel beams – that eventually failed, the Star Tribune of Minneapolis reported.

Investigators also determined that corrosion of certain gusset plates, extreme heat and shifting piers did not contribute to the bridge’s collapse, the newspaper said, citing unnamed sources with direct knowledge of the probe.

Rep. Jim Oberstar, a Minnesota Democrat, was skeptical of earlier suggestions from the NTSB that gusset plate design was responsible for the bridge collapse, and on Sunday held to that view.

“It stretches both credibility and past experience with bridge structural failure to find causation through a single factor,” Oberstar said, also criticizing the NTSB for what he said “appears to be a selective leak.”

“I can’t recall a previous leak of critical information in so serious an investigation as this one,” he said.

A spokesman for the NTSB didn’t immediately return a call Sunday. Kevin Gutknecht, spokesman for the Minnesota Department of Transportation, said his agency would wait for the official release of the report before commenting.

NTSB Chairman Mark Rosenker has indicated previously that flawed gusset plates were a focus of investigators’ efforts. According to the Star Tribune’s sources, investigators believe that if key steel gusset plates had been designed properly at an inch thick instead of half an inch thick, the bridge would have held up under tons of concrete and steel that were added in two renovation projects – and under the 287-ton construction load on the bridge the day it collapsed.

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