The Minnesota Department of Transportation has had visual evidence of damaged gusset plates on the 35W bridge for more than four years, according to a Star Tribune report. It appears that URS Corp., the company that MnDOT hired to look at the structural stability of the bridge, took the images for the department in the summer of 2003.
In January, the National Transportation Safety Board suggested that the bridge failed because of a faulty design, namely that the gusset plates were too thin. Those gusset plates are shown to be bowing under pressure in the photos by URS in 2003.
Last fall, the paper reported that the same consultants that provided MnDOT the photos as part of their inspection also made recommendations about the steel plating:
“MnDOT considered the steel plating at the recommendation of consulting engineers who told the agency that there were two ways to keep the bridge safe: Make repairs throughout the 40-year-old steel arched bridge or inspect it closely enough to find flaws that might become cracks and then bolt the steel plating only on those sections.” The inspection route, instead of reinforcing the steel plates, was the cheaper option and the one the department pursued.
In a similar situation, MnDOT closed a major bridge in St. Cloud this weekend because an “inspection showed the gusset plates, metal plates used to reinforce bridge joints, had bent one-quarter of an inch.”
The 2003 photos of the 35W bridge, available at The Star Tribune, show bending of more than a quarter of an inch at at least two joints.