Concrete Foundations for Wooden Bridge

[tpaulson]

See this web page for info on timber bridges.

http://www.extension.umn.edu/distribution/naturalresources/DD7005.html

 

[Mark_in_IN]

What do you mean by cross ties?

mark

 

[bgott]

Railroad ties...the wood under the rails.

 

[Anonymous Poster]

You can see the bridge I built over the stream out back and a description at:

http://www.connix.com/~aboursy/bridge.html

I used a reinforced concrete pad 12" to 16" thick set into the ground a few inches. The arched 28 foot span is made from pressure treated wood laminated into a 21" high I beam shape with epoxy and screws. There are 3 beams and the bridge is 5 feet wide with 2x6 decking. There is a 5 foot access ramp on one end and an 11 foot access ramp on the other end making the overall length 44 feet. The pictures do not show the railings that were added shortly after the photos were taken. They are also laminated and smoothly curved like the bridge. I built it as a foot bridge in 1995 before I had a tractor, but I have taken my B2400 across it without a problem, although it is a tight fit width wise. I placed the bridge in a spot where some large trees on each bank would stop it from going down stream in the event of washout. I piled stones on the bank between the foundation and the water and around the foundation to prevent washout. I was worried that the pad foundations would move relative to each other and put stress on the bridge so I took carefull measurements of the pads distance apart (bank to bank) on each side after I built it. I measured several times again over the next couple of years, spring, summer and winter with the ground wet, dry and frozen and the distance was always exactly the same.

Andy

 

[Mark_in_IN]

Wooden Bridge

O.k. another question, I found out that the only poles i can get have either broken off or rotted off, so is it o.k to maybe splice the poles together to use shorter poles? Will it loose alot of strength?
I measured last night and the banks of my creek are 30 feet apart. but the creek itself is only 2 feet wide yet can swell to over 20 feet, so i really don't want to put any posts as support in the center.

please offer some suggestions

mark

<P ID="edit"><FONT SIZE=-1>Edited by Mark_in_IN on 10/10/01 11:36 AM (server time).</FONT></P>

 

[MarkV]

Re: Wooden Bridge

Mark-30 feet is a pretty good span. I think you would lose to much strength with a splice that does not have any additional support to it.

In another thread about barn building a site was mentioned that offers "building basics for bridges" that you may want to check out.

http://www.southernpine.com/constructionguides.htm

Good luck with the project.

MarkV

 

[jedens]

gatorboy,
I'm very interested in your project. It sounds like what I'm thinking about also. Let us know how it goes and what luck you are having in locating the poles.
thanks
Joe

 

[DAP]

Glen, I read some but not all of the posts, so I may duplicate someone's idea.

Actually, since you are dealing with mother nature here, most of the approaches seem to involve the 'brute force' method of trying to place a 'fixed' structure over a very unfixed and dynamic obstacle.

As such, my approach, as a basis for first thoughts, would be to make my structure as dynamic as the obstacle, or at least as much in concept as possible.

In other words ... why afix this structure to the creek banks. Guess what, they may very well be in a different position next year.

I suggest 'floating' a span ... (I don't mean floating it in the creek either) ... perhaps a modular approach of 2 sections or since your only spanning 8-12 feet (could be larger after heavy wet seaons) a single section that is superficially attached to earth apron on each end of the creek.

This movable plank could be supported mid-center of the span from the underside using some type of light but strong frame work.

This forum nor time prevents a complete design, but I'm trying to offer a general idea as an alternative to typical span and poured footing approaches based mostly on the fact that the creek maybe not where ya left it next year!

Just a thought.

Doug