Originally posted by: Atomicus
Originally posted by: Howard
Originally posted by: Martin
you have probably figured this out already, but nevertheless: According to this
http://www.woodbin.com/ref/wood/strength_defs.htm
wood is much better in compression, so whatever truss you use to build it, put it on top the bridge.
I'm thinking that if you put the truss atop the bridge, you'll get more tensile loading.
It doesn't matter; it will have both tension and compressive forces on members.
Use West Point Bridge Designer to figure out which members have the highest compression and compression and design those as the biggest since they will need the strength.
If there are no restraints as to the # of supports beneath the deck, then I'd use that loophole to my advantage and just place a ton of supports beneath.