5 Years After Collapse, Beefed Up Bridge Inspections in U.S.
Five years after the Interstate 35W bridge collapsed into the Mississippi River in downtown Minneapolis, bridge inspections in Minnesota and across the country have been strengthened, leading to "minimized" risk of another bridge failure, some experts believe.
"We've made a lot of advances in the way of bridge safety," Nancy Daubenberger, who heads the Bridge Office at the Minnesota Department of Transportation, told 5 EYEWITNESS NEWS on Tuesday.
Among the changes:
- Gusset plates, the crucial pieces that hold together load-bearing members on bridges such as the one that collapsed in Minneapolis, must now be included in a bridge's load rating, determining how much a bridge can safely hold. The National Transportation Safety Board concluded the gusset plates on the 35W bridge were incorrectly designed four decades ago and only half as thick as they were supposed to be. The National Manual for Bridge Evaluation has now been changed to include analysis of gusset plates in load ratings for bridges that still use them.
- The amount of construction equipment allowed to sit on a bridge deck is now limited, with Minnesota transportation officials given greater authority to enforce such limits. The NTSB concluded construction equipment resting on the 35W bridge deck was a contributing factor in the collapse.
- In Minnesota, transportation officials are working on improving testing techniques to better inspect for corrosion that the eye cannot detect. MnDOT has been conducting research into advanced bridge monitoring techniques such as acoustic emissions and infrared thermography, which is in place on the new 35W bridge span.
- Minnesota also now requires independent reviews of design work on major or complex structures. The separate consultant contracts do cost the state more money but Daubenberger, herself a bridge designer, thinks "it is money well spent."
In addition, the frequency of inspections of fracture-critical bridges has been doubled, to once every two years. That step had been recommended by the NTSB but had not yet been implemented at the time of the 35W bridge collapse.
On Wednesday, the chairman of the NTSB posted a blog to mark the bridge collapse anniversary, and summarized some of the nationwide changes.
Garrett Ebling, a bridge survivor who wrote a book published this month titled 'Collapsed', said the changes to bridge inspections may save lives.
"I definitely think this is making things safer," Ebling said in an interview beneath the bridge span.
"I think it's important for most, if not all, bridge survivors that at least one of the good things that can come out of (the bridge collapse) is that we have greater awareness to the issue and that things are getting fixed faster."
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