But that's the beauty of it! You can make those pylons anywhere, truck them in, and install them in whatever order you want. It's construction....that scales up almost effortlessly.
For scale, you know those 4' by 4' by 8' blocks of cement you see all over the place, used for erosion control and the like? They're called ecology blocks, they're about $20 each FOB the cement plant. You want them shipped? A lowboy can carry two or four at a time without exceeding load limits. When I looked into buying a couple hundred, having them shipped about sixteen miles, it was going to cost hundreds per block to truck it out plus renting a crane to unload/place them.
Those are tiny blocks with almost no rebar, no engineering, no preload, nothing.
Again, dunno if it's feasible over long distance, but it's certainly done. (Though Texas has a certain affinity to overpasses that borders on the pathological, fun as they are to bike over...)
a 4' x 4' x 8' ecology block is about five yards. So let's picture the pylon having a 4' x 4' base that sits on granite, requiring no foundation. The pylon is going to max out at 16 or 32 feet tall if we're required to stay within the load limits.
furthermore, when you see those ribs moving around, they're moving around on interstates or state roads of solid construction. If there was an interstate running directly from San Francisco to Los Angeles along this route, we wouldn't be having the discussion. Building such a road to deliver precast sections is quite the endeavor.
I stand by my original claim that these would need to be cast-in-place.
Umm, that's kind of the point. It's called I-5.
That's just brilliant. (for the rest of the world 1,201,202.4m is 3.5m^3 and density of concrete is around 2400 kg/m^3)
It's just fascinating to me that the most expensive thing (in aggregate) is also the "dumbest" part.