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Author Topic: Rough cut lumber bridge deck  (Read 8363 times)

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Offline nay-aug

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Rough cut lumber bridge deck
« on: July 16, 2009, 07:32:41 am »
Hello All,

This is my first post!

I'm building a bridge over a creek that will span 28". Concrete footings on both sides and telephone poles for the main beams. I'd like to use 2 1/2" or 3" rough cut lumber for the deck boards, but I have no idea what wood would be best or thickness. A local sawmill suggested Beech, saying that is a hard wood that will last. They even tell me they can have it Wolmanized for an additional 20 cents per board foot. I looking for help on lumber type, thickness, wolmanizing, and even the use of telephone poles for the main beams.

This is a acess road to my camp and will see normal vehicle traffic.

I'm a total rookie at this, any and all comments welcomed.

Best regards, Al

Offline jdtuttle

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Re: Rough cut lumber bridge deck
« Reply #1 on: July 16, 2009, 08:02:03 am »
28 inches or 28 feet? ;D ;D. If it's 28 feet that's a pretty long span for a pole that was meant to stand straight up for loads. Maybe someone with an engineering background will chime in. What's the width of the bridge & how many poles do you have? This is a great place to do a little research :P
jim
Have a great day

Offline nay-aug

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Re: Rough cut lumber bridge deck
« Reply #2 on: July 16, 2009, 08:15:51 am »
Hello Jim,

Thanks for replying. Yes, it is 28 feet. I was planning on using 4 or 6 poles, because I have them available. They are 8" to 9" in diameter. I could purchase some rough cut timbers if that would make a better bridge. Deck width will be 12'. I'm wide open on this project and looking for suggestions.

Any thoughts on the deck boards?

Regards, Al

Offline jdtuttle

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Re: Rough cut lumber bridge deck
« Reply #3 on: July 16, 2009, 08:30:15 am »
http://www.bridgesite.com/funand.htm
Check out this site. You will need to do load calculations of the vehicles that will be traveling over the bridge. 9" poles spanning 28' may not be adequate without some type of truss or suspension design incorporated. Know any engineers that can calculale loads? :)
jim
Have a great day

Offline Brad_bb

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Re: Rough cut lumber bridge deck
« Reply #4 on: July 16, 2009, 09:02:18 am »
If you are planning to put vehicles over it, I don't think you will be able to lay down poles and nail deck boards down to them.  It will take some real design (trusses) and joinery.  Beech is a great hardwood for a timberframe if it's good quality, but it's not rot resistant.  Probably White oak for the structure.  Deckboards options are up to you, depending on the upkeep tolerated, amount of use, etc.  I'd consider if you really need 12 ft wide.  You can do it, but 8 feet would be less load and a little easier on the design.
Anything someone can design, I can sure figure out how to fix!
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Offline pineywoods

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Re: Rough cut lumber bridge deck
« Reply #5 on: July 16, 2009, 09:19:53 am »
Go to my photo gallery, there's pics of just such a project, just a little shorter. There's posts on here somewhere, do a search on building a bridge. I used 6  6X12 pressure treated pine, deck is full 2 inch heart pine, pressure treated. Look down the left side of the screen, there's a little red toolbox. click on that and scroll down to DonP's calcs. There's formulas there for calculating load bearing loads for solid beams. You can get away with deck nails to fasten down the deck, just use big ones. We run a dozer over ours and it ain't fell in the creek yet  ;D ;D  I don't think the poles will do the job. Whatever you use, make sure is treated against rot..
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Offline nay-aug

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Re: Rough cut lumber bridge deck
« Reply #6 on: July 16, 2009, 10:01:47 am »
Thanks Gents,

Great comments on the main beams, I'll do the calculations and rethink these beams.

Any more thoughts on the decks boards. What lumber would be rot resistant?  I'm planning on having it treated as well.

Best regards, Al

Offline DanG

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Re: Rough cut lumber bridge deck
« Reply #7 on: July 16, 2009, 10:22:05 am »
Hey Nay, and welcome to the forum. :) :)

Is there any way you could put some intermediate pilings under there to shorten the span, or is the actual stream 28 feet wide?  I'm thinking even if you could place them four feet from each end you would cut the span to 20', and some well made knee braces would shorten it even more.
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Offline nay-aug

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Re: Rough cut lumber bridge deck
« Reply #8 on: July 16, 2009, 10:36:00 am »
Hello Dan G,

Yes, on the one side I can get additional support and shorten the span to 19 or 20 feet.  I'll do the calculations as someone else has suggested.

Any thoughts on the deck board material?

Best regards, Al

Offline MSU_Keith

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Re: Rough cut lumber bridge deck
« Reply #9 on: July 16, 2009, 10:37:42 am »
A publication that helped me greatly is the timber bridge document located here:
http://www.fpl.fs.fed.us/products/publications/pubs_interest.php

It has descriptions of all the various calculations needed to design simple and more complex bridge structures including static and dynamic loads, flex limits, shear limits, abutment requirements, etc.  

My span is 12'  with 5 - 12" x 8" x 15' WO timbers connected to poured 12" round piers.  Decking is 2" WO in the middle with the entrance and exit 'ramp' decking wolmanized.  Side beams have a truss/railing that also provides support.


Offline DanG

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Re: Rough cut lumber bridge deck
« Reply #10 on: July 16, 2009, 12:58:49 pm »

Any thoughts on the deck board material?



Without knowing where you are, it's hard to know what might be available.  Basically, anything they use for RR ties should work.  The beech should be fine if you have it treated, as mentioned.  Also, sycamore and sweetgum are known to take treatment well.

I'm also thinking, if you have a creek and need a bridge, you also might have some trees.  You could save a big roll of cash by cutting your own and hiring a sawyer to make your beams. ;)
"I don't feel like an old man.  I feel like a young man who has something wrong with him."  Dick Cavett
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Offline nay-aug

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Re: Rough cut lumber bridge deck
« Reply #11 on: July 16, 2009, 01:28:34 pm »
DanG,

I live in Northwestern Pa., about 60 miles north of Pittsburgh.  The parcel of land I'm talking about has a good stock of trees, mostly Maple. I think Silver Maple! How would that be for main beams and deck boards?

The guy with the Beech quoted me 60 cents a board ft. for 2 1/2" thick x 8", 10" & 12" random widths. I need enough to cover approx. 28' long by 12' wide. Plus another 20 cents per board ft. to pressure treat it. I didn't think that was too bad.

Regards, Al

Offline DanG

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Re: Rough cut lumber bridge deck
« Reply #12 on: July 16, 2009, 01:43:42 pm »
I can't answer your question about the maple, but there are plenty of folks here that can. ;)

80 cents isn't a bad price at all for the p/t beech.  All I'm saying is, you could get it even cheaper if you wanted to use your own trees.  You wouldn't believe how many people have ended up with their own sawmill after having some custom sawing done.  Just planting a few seeds for thought. ::) ;D :D
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Offline jdtuttle

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Re: Rough cut lumber bridge deck
« Reply #13 on: July 16, 2009, 03:02:25 pm »
I'm in NY and have sawn white oak for bridge deck boards.
jim
Have a great day

Offline Brad_bb

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Re: Rough cut lumber bridge deck
« Reply #14 on: July 17, 2009, 10:47:22 pm »
Silver Maple, no good for beams or much of anything else.  It's soft and not very strong.  White oak is, of course one of the best choices due to it's resistance to rot and strength.  You don't need to treat it.  If you are trying to do a really nice job of it, keep it from touching the concrete pilings.  Use something as a barrier between them to keep moisture off the beams. 
Anything someone can design, I can sure figure out how to fix!
If I say it\\\\\\\'s going to take so long, multiply that by at least 3!

Offline Meadows Miller

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Re: Rough cut lumber bridge deck
« Reply #15 on: July 18, 2009, 06:24:10 am »
Gday

Welcome to the forum Nay-aug You have come to the rite place Mate  ;) ;D ;D 8) 8)

With the poles overhere H/wood to span that distance on a Major/minor road is about 16" to 18" dia midpoint or the same size in a hexagon with the sapwood removed  they are fun to saw  ::) 4 of them will cope with two semis   hitting it at 62mph at peak load  ;)

I can't answer your question about the maple, but there are plenty of folks here that can. ;)

80 cents isn't a bad price at all for the p/t beech.  All I'm saying is, you could get it even cheaper if you wanted to use your own trees.  You wouldn't believe how many people have ended up with their own sawmill after having some custom sawing done.  Just planting a few seeds for thought. ::) ;D :D

DanG We arnt leading another bloke astray are we Mate  ;) :D :D ;D Its pretty simple math to us  ;) :D Want Brige + Have Trees = Buy Mill , Learn how to use it Here  ;) , Mill timber and  Build Bridge and the most important part  ;) Keep Mill for other projects Does  That sound about rite Mate  ??? ;) :D ;D

Reguards Chris



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Offline tyb525

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Re: Rough cut lumber bridge deck
« Reply #16 on: July 18, 2009, 10:36:45 am »
Chris your reasoning is flawless ;)
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Offline SwampDonkey

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Re: Rough cut lumber bridge deck
« Reply #17 on: July 18, 2009, 05:49:28 pm »
Can you use an old truck frame and use beech or white oak as decking? Grandfather always used white ash on his bridges. I mentioned the truck frame because they use them around here, probably not longer than 16 feet however. Anyone got an old junked logging trailer frame? I seen one the other day on a vacant lot that would span that creek. ;D

Pre-commercial thinning pays off. :)

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Offline Rooster

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Re: Rough cut lumber bridge deck
« Reply #18 on: July 18, 2009, 07:40:05 pm »
Al,

Welcome!  I am also fairly new to this forum.  And I have to say that the members here that post regularly are very supportive and also very practical.  I see that you were having a hard time getting these guys to chime in on a suitable decking material.  And all the replies were focused on your choice of support structure.  It makes sense when you think about it, they are just trying to steer you in the right direction.  The best decking choice in the world is not going to help you any when it's laying in a pile at the bottom of your ravine.   ;)

Also remember that there are a lot of FF members who have't seen your post yet, who might be able to answer the rest of your questions..just give it some time.

I also saw a farm bridge made out of a couple of used flatbed semi trailers, side by side.....and they were decked with White Oak. ;D

Good luck, and keep asking questions, these guys are the best!

Rooster
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Offline sbishop

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Re: Rough cut lumber bridge deck
« Reply #19 on: July 19, 2009, 06:28:13 am »
Swampdonkey, i've seen them use an old school bus frame!

Sbishop