When the Minnesota Department of Transportation closed the Hwy. 43 bridge in Winona on June 3, it said it was doing so because corrosion had been discovered on several of the bridge's gusset plates.
In many cases, the rust was actually rediscovered.
A MnDOT inspection report from April 2007 -- months before the collapse of the Interstate 35W bridge in Minneapolis -- noted that one of the Winona gussets had rusted all the way through and that several others had thinned because of corrosion. This didn't raise alarms within MnDOT because gussets weren't considered as troublesome at the time.
Then in January 2008, the National Transportation Safety Board said that a failure of gusset plates was suspected in the 35W bridge collapse, triggering inspections and analysis of about 25 steel deck truss bridges across Minnesota.
When the Hwy. 43 bridge's turn came, it was abruptly shut down as a precaution after inspectors noted the thinned gussets and one bent one. The 67-year-old bridge has since reopened to passenger vehicles and is undergoing repairs and bolstering.
In addition to cataloging the condition of gussets, the April 16, 2007, "snooper report" -- available on MnDOT's website -- found that pack rust was pushing some pieces of the bridge apart, and inspectors noted that two of the bridge's bearings "are not functioning as designed" and said replacement should be considered.
JIM FOTI
