[Paladin2]

Steel has a pretty cool property, IIRC called the fatigue limit. If a structure is designed to have its stresses below this limit, the fatigue life is infinite (as opposed to Aluminum which doesn’t have this property - see old airplanes having their wings replaced)

Steel in the absence of corrosion and in appropriate designs should last nearly forever.

I believe that I read that this bridge had an automatic corrosion de-icing system installed to help get through MN winters. Looking at the design of the bridge, all drainage looked to be directed towards the ends of the main span arch, which seems to be near where the initial failure(s) occurred.

[Doe Eyes]

automatic corrosion de-icing system

Please post some information on the corrosive properties of this de-icing system.