Digital Imaging Correlation Helping Engineers Examine Bridge Failure in “Exquisite Detail”

It will be five years on the first of August since the Interstate 35-W bridge in Minneapolis, Minnesota fatally failed leaving 13 dead and dozens injured. If any cloud truly has a silver lining, the sterling behind this tragedy may be the momentum it has provided in helping to assure that hundreds of bridges across the U.S. are safe.

An investigation conducted by the National Transportation Safety Board (NTSB), determined that gusset plates were the “immediate culprit” behind the 2007 collapse in Minneapolis, according to Federal Highway Administration (FHWA) engineer Justin Ocel. Together with the FHWA and the American Association of State Highway and Transportation Officials (AASHTO), engineer Mark Iadicola of the National Institute of Standards and Technology (NIST) is therefore working to understand and document the failure of gusset plates with the help of digital image correlation.

The NIST digital image correlation method is a good complement to the FHWA measurement methods. Their techniques—strain gages and photoelasticity—are very good for the normal range of stress in which the plate will stretch and spring right back to its original shape. Our method can tell you a little about that, but it really shines in showing you what happens past that point, when the plate starts permanently deforming and finally rips apart.”

— Mark Iadicola, NIST

The FHWA and AASHTO are now working together to incorporate what they’ve learned into the AASHTO Bridge Design Specification and the Manual for Bridge Evaluation, which are used in bridge design and rating across the U.S.

The January 11 NIST press release is at

Also, check out the NIST video at

© Tony Leininger and IT for Good 2012. See sidebar for full copyright notice.

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