Bridge design and engineering, how?

[v8dave]

A bridge project or two will likely work its way to the top of the list in the next several months. Anybody have pointers to web pages or books in print on how to engineer one?

I have a small seasonal stream to cross in possibly two places. Both for foot and tractor traffic (tractor around ~3,000 pounds). The bank to bank span would be 10' to 15'. Although, an inverted 4' half culvert would allow adequate stream flow. Upstream source is only a 2' culvert.

I suppose the brute force approach would be to get a pair of 12" I beams, weld up a ladder between them and plank it. I am hoping for at least one of these (the one viewable from the house) to be a little picturesque.

 

[BB_TX]

Dave - If you will do a search for bridge, you will find several threads on bridge building. Don't remember any plans, but there have been a number of pictures of different bridges people have built, both with large culverts and using steel I beams. Also at least one using salvaged flat bed trailers. I am planning a bridge also so I have watched these posts with interest. Search all forums back as far as at least a year as they have been in different forums at different times.

 

[Henro]

My "bridge" building experience is limited to a small 7 foot span that crossed a little ditch...was made from some steel piling a couple I beams.

It is now replaced with a piece of 18" ID culvert pipe. If you can put a pipe in and fill over it, I think you will get the job done easier and faster, and in my opinion better. I say better because if you would use a longer piece of pipe (I used 20') you end up with something tha will support whatever weight you put on it, and something that is much wider than any bridge you would probably build...

My little bridge would handle my B2910 Kubota TLB, but I don't miss it and if the option is there, I choose pipe. I put a second 20' piece in this summer, a little "up stream" from the first one here...if you need more flow you could always put several smaller pipes in side-by-side, rather than one large one...

But you asked about bridges, not pipes... /forums/images/graemlins/blush.gif

 

[MicroPilot]

I like this idea. You could even face it with a rock veneer to make it look like a rock bridge!

 

[Soundguy]

I havn't seen your area, but let me stress that you can't overdesign a bridge enough.. if you know what I mean.

Check the Army corps of eng's handbook.. should be lots of 'improvised' structures in there.. possibly a bridge design or two as I remember.

Large box culvert makes a good bridge.

The GC I work for has done quite a few jobs placing box culvert sectons in as roadway.

Soundguy

 

[Freds]

How did you figure the 4' culvert and why would you need one if you are building a bridge?

The reason I ask is because I have a seasonal creek, also, that I needed to across. The contractor that needed to cross it had me send in a check with his intended use to the PA something or rather and they sent back the plans on how it needed constructed. We were going to fill it in with gravel to drive across and even though the culvert pipe upstream is only 2' diameter, I needed a 3' diameter pipe plus all kinds of landscaping to prevent bank errosion.
After my project was done I had him rip it back out. It was only in half-a**ed anyway and the culvert was smaller than what the state told him to use. I can ford it with no problem and prefer the look of the creek.

I don't understand why you would need the culvert if you are building a true bridge and not filling it in like we did.

 

[SPIKER]

I would do the search for bridges, and fords and creeks:

lots of posts, several are in the rural living forum I think.

and there are many ways to go about it, if you WANT a bridge then they are more expensive and have more design problems than a ford or a culvert & back filling. bridges will always have a weight considerations where the fords and or culverts willnot be as concerned... we have built a few nice walking bridges as more a decoritive thing but no ENGINEER was involved. we have also build car crossing bridges but that was before the rules to home sites required that a fully loaded fire truck could get through. so now we usually don't built commercial bridges but for small golf carts and such yes we do/did to that. http://www.haynncorp.com/forsale to see a few arched ones we built for fun and a few straight/flat ones for use.

Mark M /forums/images/graemlins/smile.gif

 

[have_blue]

Build some massive wooden box beams from treated 2x12 uprights and 2x8 or so for the horizontal members. Use small but fairly deep poured concrete pads underneath each beam, and a pour in 5/8" "J" bolts to anchor the beams.

If you want a handsome clear-span arched bridge, stack another pair of 2x12's atop the box beams, sawn to the proper curvature with a HUGE JIGSAW /forums/images/graemlins/smile.gif . Use treated 2x6 for the crowned roadway, leaving 1/8" gap between the boards. Bolt treated 2x4 railing uprights to the arches, using steel or heavy aluminum clips or angles. Cap the uprights with a nicely curved 2x4 hand railing. Paint the box beams and/or arches with spar varnish or marine paint, and cap the arches with copper or aluminum flashing to prevent water collection and eventual rot. This setup is scalable. It's as strong as you like, and as plain or or as pretty as you like. You can make handsome trusswork for the hand railings if you want a pretty bridge. Expensive, yes. But it leaves a little piece of you behind for the grandchildren. /forums/images/graemlins/smile.gif

 

[em14]

For the requirement that you described I think I would put in a culvert (s) and use a rip rap protection on the sides. If you can find a copy of Army FM 5-34 that is a great little manual that covers just about everything a farmer would need to know to handle roads, bridges and a mutlitude of only needs. Try this site: http://www.apd.army.mil. I think the Army has changed the way I am use to getting to their info ... They are a great source of information TBNers need.
Leo

 

[v8dave]

</font><font color="blueclass=small">( I like this idea. You could even face it with a rock veneer to make it look like a rock bridge! )</font>

That is exactly how I would do it if I ended up with using a half culvert--face it off to look like a rock bridge.