Ewwww.

So those are MIG welding robots. They've been around for... 50 years?

What's new is the idea that you could build a structure out of MIG wire, because the minute you bring steel up to molten and then air cool it, you have induced three properties:

1) It has deplorable yield strength (once you bend it, it's bent)

2) It has negligible corrosion resistance (it will turn brown with rust in a week in the Nevada desert)

3) It is fundamentally devoid of tensile strength (it might as well be coat hanger wire)

Their process also allows it to have a crappy, porous finish, too. When one MIG welds, the parent metal is an important part of the process because you're only fucking with its metallurgy, rather than annihilating it. When you're just making a bead, you're basically making slag.

I have no doubts that they will successfully construct a bridge. I also have no doubts that they will construct a bridge for a great deal more expense a great deal slower than a conventionally-made bridge.

There are better choices for 3d printing bridges...