How to build a 50' Clearspan bridge

Title says it all. The section of my pond that necks down is 50' wide. I would like to build a bridge that is strong enough to support a UTV. It doesn't have to be clearspan but then I would have to drive large pilings out in the water. It also has to be high enough for boats to go underneath...I thought about just making a land bridge but I do not want to loose any water area...I'm not asking much $\:\)$

Sgt911, the frame of a mobile home should be able to support several ton without problem.

something along these lines could be the basis for one: 50' steel beams I don't think wood is going to make it that far without some center supports.

I'm not a fan of mobile home parts for anything. The secret to mobile homes is that they are made light and they are made quickly. They are not designed for allot of travel, and they have a terrible history of falling apart while just sitting still with cement blocks all over the place to support them. I wouldn't even guess what thee frame could support at the center when supported on either end, but I bet it's not going to be very much. Add the lumber to create a deck on the bridge and you're probably near the limits of what the frame can support.

Ideally, a 54 foot flatbed trailer would be perfect if you could find one for a reasonable price. Odds are that it would be a rare find, but you never know.

There are some charts and of course, engineers out there that can tell you the size of a pair of I beams that will support the weight of a UTV at midspan. Once you know the size you need for the beams, the rest should be easy.

Good luck,
Eddie

You don't mention a budget but we've done it with pre-cast double-t beams. There used to be a pre-cast outfit down your way. They use these things for the decks on parking garages among other things. http://www.tpub.com/content/engineering/14069/css/14069_253.htm
If it's a "do it yourself" and cost is a big issue then some kind of steel truss is probably going to be the most inexpensive way. For that matter you may be able to find some a couple of steel joist sitting in a yard somewhere like these.
http://www.vulcraft.com/downlds/catalogs/joistcat.pdf

What a beam will hold (yield) isn't the only conderation. A small beam will hold a lot but can be very bouncy. A truss would be a lot cheaper. Check with a steel building manufacturer that builds trusses like http://www.kbuildings.com/spotlight.asp

This company would hang a corvette from one of their trusses at the Farm Science Review to get attention.

The size of the equipment required to set a truss vs beam will typically be alot less expensive as well.

Something like this�
http://utilityoffroad.com/forum/topic.asp?TOPIC_ID=16892

Jim, that's it..I might have to pick a shorter span to cross, I have another shorter spot but I did want to remove the existing dock, plus it would be cool to drive across the wider expanse. Thanks everyone

You don't happen to know anyone in the engineering department of a local college, do you? Looks like a good design project for a young engineer in training. When I was a freshman at an engineering school in Southern New York, I helped out as labor to a senior building something like this for her design project, but it was a much smaller span on a golf course.

The truck trailer is a good idea. You might have more options if you fill in a little bit on the edges to cut the span to 35-40', which will still give you plenty to work with.

Exactly what I was thinking Jim.

My bridge is 24ft and like you, I wanted boats to be able to go underneath. I called around and consulted with several engineers primarily for the design. I should have also focused on how it would be moved and installed once fabricated. Here are some things I learned that may help:

-Make sure you are able to get the bridge out of the structure where it is fabricated so you don't have to disassemble.
-Have a plan for moving it.
-Know how much it will weigh.

Having never done anything like this before...I learned allot through my mistakes $\:\)$

Very nice Cheezy

thanks. I would like to add that one disadvantage of an arch bridge is that is becomes difficult to cross when there is ice.

How about 150 feet?

I built a 200ft suspension bridge across the narrow part of my pond. I used 4 inch steel pipe 30 ft long for my uprights. I really don't have a lot of money in it. I had 8inch of wet snow on it and it held. I put lights on the uprights and cable and it looks like the Golden Gate bridge with the reflection in the water at night.
Cooper in NC

Wayne, you may very well have made one of the most original first posts in the Pond Boss forum. I have always thought that a suspension bridge is the way to go for longer spans. Consummate your creative arrival by posting a few pics.
....please?

Plus one on the photo request. Suspension bridges are so cool.

I do not know how to put pictures on the forum. Is there a tutorial? I will take some pictures this weekend. I really had fun building it. In fact, I built it 4 times. (I learn real slowly) I will build a new bridge for our new lake. I think I know now how to improve it. I had 8 inches of wet snow on it and it held. It is 4 ft wide,I forget what a friend calculated the weight was, but it was a lot. thanks for the nice welcome
Wayne

Hang on Wayne,and someone will post a link to the pic post thread.

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First topic

A 50 foot bridge is very possible with a truss construction. And I bet the truss would only have to be about 4 feet high. An engineering student would be a good place to tap into if you know one or perhaps contact a school and see if a prof has any design students who need a project. Or, I know I have found a web site before that will show you how to design and optimize a truss for whatever load you need. I think you can download the software. Then you can start with whatever material you think you can find and conduct the proper analysis yourself to design the bridge. I'll see if I can find where I got that software but I'm guessing if you google it you can find it.

I found it, the program is called AMSES Frame and can be found at:
http://www.brothersoft.com/downloads/amses-frame-2d-demo.html

I have the free download and it appears easy to use although I have not worked to do a complete design yet. If you are a DIY kind of person and have a basic understanding of structural stuff I think you can do this.