NTSB cites design flaw in I-35W bridge collapse

WASHINGTON, D.C. — The National Transportation Safety Board (NTSB) today issued a safety recommendation that addresses a design issue with the Minneapolis I-35W bridge, which collapsed into the Mississippi River in August.

The accident killed 13 people and injured 145. Among the vehicles on the bridge was a school bus carrying more than 60 passengers, but all were safely evacuated.

"Although the board's investigation is still ongoing and no determination of probable cause has been reached, interim findings in the investigation have revealed a safety issue that warrants attention," said NTSB Chairman Mark V. Rosenker. "During the wreckage recovery, investigators discovered that gusset plates at eight different joint locations in the main center span were fractured.”

The NTSB and the Federal Highway Administration (FHWA) reviewed the design of the bridge, with an emphasis on the design of the gusset plates. The review discovered that the original design process of the I-35W bridge led to a critical error in sizing some of the gusset plates in the main truss.

The recommendation, made to the FHWA and states, calls for bridge owners to conduct load capacity calculations before making modifications. To read the full recommendation, click here.