I stayed up half the night trying to engineer this thing. What I can see drilling 2 9" post holes on either side of the creek. Have to try to get them square with one another, which is a problem because the creek is pretty much impassible when it has water in it, and fairly difficult to cross right here even when its dry, due to steep creek banks.
The posts (some sort of metal posts I guess - something like water well casing depending on cost) would be cemented. Then about a foot-deep hole would be excavated between each pair of posts and some reoar put in there. Then, build forms to build up the footings another foot or so, so that the concrete is 2 feet thick.
Depending on design, if the beams need to be anchored to the footings themselves, then threaded studs will need to be set in the top of the footings in the exact locations needed, to bolt the beams down to.
As an alternative, using an all metal frame design, all of the frame could be welded between each pair of metal poles, and the rest of the concrete footing might not even be necessary at all. My PHD will dig about 36" deep, hopefully that would be deep enough to anchor the posts. Perhaps a 12" auger is needed.
The Kawasaki mule that I currently own weighs about 1200 pounds, so with two people in it, and some cargo, figure 2000 pounds. The bridge will primarily be for foot traffic however.
The arched design Wroughtn_Harv is describing sounds very good to me, although its sounds like a lot of sawing and welding on his part. The bridge will need some handrails also (so my grandchildren don't fall in the creek), which would seem difficult in an arched design since everything has to be curved.
I would be perfectly happy with a straight, not arched bridge as my second choice. If its 6 feet wide, it would seem to need four beams, so the decking would only span 24" between beams.
When the bridge is done, later on I plan to run a water line across the creek, and figured the structure of the bridge would be the logical place to run it, although I would need some way to keep the pipes from freezing.
Am I correct in assuming the cement anchoring the posts would need to be set up before any major work is done on the span? Assuming this, it would seem that this would need to be done ahead of time. This might only consist of setting 4 posts, no other concrete footings at all. Also, I suppose the posts could be left sticking up at lease as high as the handrails would be, then cut off later to the proper height.
Of course about July is the driest time to be working on the creek, but it is also pretty dang HOT about then.....
This is the stuff that kept me up all night......
