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Design Flaw Cited in Bridge Collapse

Divers search for victims near the Interstate 35W bridge which collapsed ove...

By FREDERIC J. FROMMER, AP
50 minutes ago

WASHINGTON — Undersized gusset plates in the Interstate 35-W bridge in Minneapolis were "the critical factor" in the bridge collapse last year that killed 13 people and injured 100, the National Transportation Safety Board said Tuesday.

Chairman Mark Rosenker said the plates, which connected steel beams, were roughly half the thickness they should have been because of a design error. Investigators found 16 fractured gusset plates from the bridge's center span, he said.

"It is the undersizing of the design which we believe is the critical factor here. It is the critical factor that began the process of this collapse. That's what failed," Rosenker said.

The Minneapolis bridge was a steel-deck truss bridge that opened in 1967. Rosenker said it wasn't clear how the design flaw made it into the bridge because investigators couldn't find the design calculations.