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Last report due on Minn. bridge collapse

Nov. 6, 2008

The National Transportation Safety Board (NTSB) will release their final report the week of Nov. 10 on 2007’s fatal highway bridge Collapse in Minneapolis.

According to a preliminary announcement, the NTSB is expected to reveal that the collapse was due to a design flaw that left the steel bridge weak at critical points.

The results are likely to initiate calls for more spending on the nation’s bridges, say civil engineering groups.

The National Transportation Safety Board (NTSB) will release their final report the week of Nov. 10 on 2007’s fatal highway bridge Collapse in Minneapolis.

According to a preliminary announcement, the NTSB is expected to reveal that the collapse was due to a design flaw that left the steel bridge weak at critical points.

The results are likely to initiate calls for more spending on the nation’s bridges, say civil engineering groups.

The investigation "did focus attention on the conditions of bridges across the country," said Andrew Herrmann, an engineer at the firm Hardesty & Hanover and a member of the American Society of Civil Engineers board of directors. "Hopefully, it will lead to more funding for deficient bridges."

Several issues argue for additional spending on bridge safety, according to leading engineers, including University of California-Berkeley engineering professor Abolhassan Astaneh, who works for a law firm that represents victims in the collapse.

Among some of the potential issues:

According to photos released in the investigation, key structural elements known as gusset plates were distorted at least two years before the accident. The NTSB announced in January that the plates, which hold girders together, were half as thick as they should have been and likely triggered the collapse.

The I-35W bridge was an older design that would topple if any single girder or joint failed. The failure highlights the need to more closely monitor and repair the more than 400 similar bridges across the nation, according to Herrmann.

NTSB photos of another undersize gusset plate show the plate was heavily corroded, Astaneh said. Corrosion has caused problems on other bridges in the U.S., Astaneh said.