Balanced Bridge Spans
Balanced Bridge Spans
(OP)
The term "Balanced spans" on multiple span bridges is common, but not well defined.
What is your "rule of thumb" to obtain balanced spans on bridges? where does this come from? do you know of anywhere that I can read up on this?
What is your "rule of thumb" to obtain balanced spans on bridges? where does this come from? do you know of anywhere that I can read up on this?






RE: Balanced Bridge Spans
I have a chart (somewhere)with various configurations but I can't find it. When I do, I'll post it.
RE: Balanced Bridge Spans
2 1.0:1.0
3 0.75:1.0:0.75
4 0.80:1.0:1.0:0.80
5 0.60:0.8:1.0:0.8:0.60
RE: Balanced Bridge Spans
The stated 5-span arrangement likely results in a "least weight" solution (or very close to it), but it MAY not be the most economical for today's cost structure.
For a five span structure, you should evaluate the above arrangement as well as the following:
0.8, 1.0, 1.0, 1.0, 0.8
This will have a slightly higher girder weight but the redundancy of details can save significant cost (at least in steel bridges).
RE: Balanced Bridge Spans
You may take it for granted that this would occur universally, but because of utilities or other obstacles, severly unbalanced span arrangements are more and more common. I even recall a project where an interior span never experienced positive moment.