Quote Originally Posted by mwilbert View Post
I don't think steel would be cheaper than concrete. If it were, you wouldn't see all those freeway overpasses constructed from concrete. I think that when people were constructing elevated trains or roadways in the past [[Chicago Skyway, old Boston Central Artery) they didn't have the concrete technology they have now.
A few years ago, I heard an MDOT engineer say on the radio that the cost to repaint a steel highway bridge was close to, or more than new construction cost, due to the environmental protection necessary to sandblast. I think this may be a major reason why steel isn't used as much as it used for such purposes.

I can't help but wonder about the life of pre-stressed concrete bridges like Zilwaukee or the I-280 bridge in Toledo. What do you do when they start to fail. With steel you can at least sandblast and weld.