Time for a new bridge - how to engineer?

[vtsnowedin]

I agree precast box culverts are not cheap, however a few years ago I had a double 24 inch culvert that would not handle the flow. Found a couple sections of 2 x 3 box culverts at local supplier that state wouldn't accept because tongue was damaged. Got them for not much more than transportation costs and then patched the damaged tongue after installation. Served my purpose very well and handled the flow where the double pipes would overtop.

Yes you got a bargain but to move forward on a new project you have to look at retail cost delivered to the site of new material. Last I checked (and it has been a while) box culvert had to be seven feet square to be cheaper then the equivalent round pipe.

 

[texas42]

I'm not trying to be argumentative but I go back to the OP's original post.
He has a water crossing that he needs to get loaded gravel trucks over. My suggestion is merely to look around to see what may be available locally. Sometimes you run on to a deal that will work without paying retail price. A small precast box if obtained right will solve his problem with little concern of failing under his loaded trucks and provide the drainage capacity he needs.

 

[vtsnowedin]

I'm not trying to be argumentative .

None of us are but it does sound that way more often then not. Nothing wrong with a vigorous debate especially if you can bring forward some facts to support your position.

 

[vtsnowedin]

I'm not trying to be argumentative .

None of us are but it does sound that way more often then not. Nothing wrong with a vigorous debate especially if you can bring forward some facts to support your position.

 

[JeremyL]

Well a wet Spring and complicated schedule put this project off until this week (in the heat). I finally decided on a culvert; smooth bore 12" plastic pipes side-by-side with a good covering of DGA (dense grade aggregate). Definately time to stop driving over the old wooden death-trap.

There is probably now more water moving capacity since it was pretty silted up under the old bridge. But you want to see pictures, don't you? Here you are:

 

[Egon]

:thumbsup::thumbsup::thumbsup:

 

[vtsnowedin]

Thanks for the up date. Of course we want to see the pictures of the next high water to see how well it did.

 

[zing]

Nice job and definitely safer than the old bridge. I think you should be ashamed of yourself though, for not having one picture of your tractor in this thread.

 

[vtsnowedin]

Nice job and definitely safer than the old bridge. I think you should be ashamed of yourself though, for not having one picture of your tractor in this thread.

:laughing::thumbsup:

 

[rutwad]

First, I will admit I only read the first page of this thread. But I agree with the idea of using culverts instead of a bridge. I disagree with the use of a small truck vs. a large truck.

How far is it from the top of the bridge to the bottom of the ditch? I see some suggestions for what seems to be a large culvert compared to the depth. You may be surprised to learn how much build it takes to slope up and across a culvert that extends much above the ground level. I would use more than one culvert but smaller. It currently looks like a triangle ditch, so calculate the area under the bridge and size your culverts accordingly.

You said the ditch usually has very little water flowing in which case the smaller culverts will flow more water. It is a fact that the volume of a 24" culvert is more than 2 12" culverts. However, with just 2" of water flowing, more water can move through 2 12" culverts than 1 24". The volume being approximately 24.8" and 18" respectively. But at full volume it would take 4 12" culverts to equal 1 24". 3 8" culverts allow 1/3 more than 2 12". Basically if the ditch is wide enough but not very deep, you may consider smaller culverts.