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Author Topic: Continuous prestressed concrete box beam bridges  (Read 473 times)

Tom958

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Continuous prestressed concrete box beam bridges
« on: April 05, 2020, 10:08:28 AM »

Help me out on this, please: Yesterday, I was reminded of the existence of this bridge carrying GA 306 over GA 400 at the last (for now) interchange on 400 headed north from Atlanta. Built in 1979, per bridgereports.com/1095686 it's a "continuous prestressed concrete box beam" (though joints are visible at each bent) with precast concrete deck sections (though the usual metal decking is clearly visible on Streetview).

This type of structure is fairly common in some states, though it's not dominant anywhere that I know of. But this is the only one I know of in Georgia.

I would like to know:

What the correct name for this type of bridge is.  :bigass:

Whether the beams are typically precast and erected with a crane, or cast in place on falsework.  The Georgia example was built concurrently with the road it crosses, so there was no need to work over traffic, but this 1998 example from Kentucky was surely built over traffic, which suggests precasting, and with very long spans to boot, which suggests cast in place.

What are the relative advantages and disadvantages of this type of construction? While it's odd that Georgia has only one example, it strikes me as even odder that this type of bridge should be neither vanishingly rare nor especially common in states that use it. It also doesn't seem to be especially tied to any certain time frame: here's a 2004 example from Indiana, where AASHTO beams and plate girders seem much more common lately.

 :hmmm:

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