No plans to check plates on Highway 51 bridge
The National Transportation Safety Board announced this week the gusset plates in the Minnesota bridge were half the thickness they should have been.
Gusset plates connect steel beams.
The board recommended states check the gusset plates on “fracture-critical” deck-truss bridges before making modifications or operational changes to the bridges.
Officials are investigating whether heavy construction equipment on the Minnesota bridge provided extra stress on the weak plates, causing them to snap.
The Highway 51 bridge in Fulton Township, unlike the Minnesota bridge, isn’t fracture-critical because it has three trusses holding it up instead of just two, said Finn Hubbard, bridge engineer with the Wisconsin Department of Transportation. That means if one truss experiences a fracture similar to the one in Minnesota, the bridge probably won’t collapse, he said.
Besides, there are currently no plans for construction or changes to the Highway 51 bridge, Hubbard said. Workers put a new deck on the bridge about 15 years ago, and those usually last at least 30 years, he said.
“At this time, we don’t have any plans to check the plates on the bridge,” Hubbard said.
Chances are small the design flaw in the Minnesota bridge exists in the Highway 51 bridge, Hubbard said.
In fact, the National Transportation Safety Board said there is no evidence the flaw exists anywhere else, it said in a news release Tuesday. The Aug. 1 collapse is the only bridge failure of its kind the board knows of.
“We wouldn’t expect there to be any flaws in the (Highway 51) bridge, but of course Minnesota didn’t expect any flaws, either,” Hubbard said.
The Department of Transportation installed strain gauges under the Highway 51 bridge in October to measure the amount of stress on the bridge. A consultant will continue gathering data from the gauges for the next month, and the department will probably issue a report with the results by early spring, Hubbard said.
“We haven’t found anything surprising,” he said.