National Boards > Bridges

Steel vs concrete beams

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wxfree:
I remember reading about the construction of the Chisholm Trail Parkway.  Concrete beams are preferred, presumably for the cost.  Steel beams are used where the spans are long.  As I remember, concrete beams made in a factory and then driven to the site can be up to about 150 or 160 feet.  If they're too long, it becomes too difficult to haul them around.  They can't be assembled at the site.  Steel beams can be put together with rivets or duct tape or whatever they use, so shorter pieces can be hauled in and assembled at the site.  Some of the ones over CTP are curved.  I imagine a curved beam would be a bitch to drive around, so the maximum length would be even less.

I've never seen cast-in-place beams used in new construction.  A local street bridge rebuilt about 15 years ago has pre-cast concrete beams, and the spans are about 35 to 55 feet, which seems a little over-built.

tolbs17:
This steel is already starting to rust. Do you think these beams can be painted?

Big John:

--- Quote from: tolbs17 on July 25, 2021, 05:46:25 PM ---This steel is already starting to rust. Do you think these beams can be painted?

--- End quote ---
That looks like Cor ten (weathering) steel.  It is pre-rusted with the theory it won't rust any further.  It is not meant to be painted.

tolbs17:
This flyover bridge is interesting because it uses BOTH steel and concrete on the same platform. I wonder why that is and yet steel is meant for curvy bridges. I'm surprised that this one uses both.

Here as well. Also using both. https://www.google.com/maps/@36.1372729,-79.8631596,3a,25.2y,352.76h,91t/data=!3m6!1e1!3m4!1s1ud55Zzn9O7T9WnRYa1ybQ!2e0!7i13312!8i6656

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