NTSB: Design factors in bridge collapse

11/13/2008 WASHINGTON National Transportation Safety Board investigators said Thursday that the bridge collapse was unavoidable, once the U-10 steel gusset plates failed due to a serious design flaw. They also ruled out corrosion and pre-existing cracking as factors.

A two-day board hearing now under way quickly focused on the U-10 gusset plates of the Interstate-35W bridge. The NTSB as far back as January had identified design flaws in the plates as a critical factor in the collapse.

The bridge shuddered and then tumbled into the Mississippi River on Aug. 1, 2007 during evening rush hour, killing 13 and injuring 145.