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  1. #1
    dog's best friend
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    Tell me about aluminum frame bridges

    Our local trail group is considering erecting an aluminum frame bridge at a road accessible multi use non motorized trailhead. Span of about 30 to 40 ft accross a fast running creek. Anyone have any info on these?

  2. #2
    mtbr member
    Reputation: MartinS's Avatar
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    Here is an amazing aluminium bridge built at Nipika Lodge near Kootenay National Park in BC, part of it is removable so it doesn't get torn away during the spring runoff.
    Here's their website, Lyle is a great guy to talk to regarding this sort of stuff.

    http://www.nipika.com/

    moz-screenshot-106.jpg

  3. #3
    beer thief
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    I would not limit your material selection to aluminum whether your looking for a pre-engineered structure or not, as steel and/or wood structures may be more economical. The easy accessibility to your site means you can pick any material, as transporting the bridge is a non-issue. If you have a local engineer that can design your bridge you can also have local fabricators/contractors build it, which will save shipping costs (which are significant these days).

    A quick google brings up Gator Bridge, a manufacturer of aluminum bridges. There aren't that many companies that make aluminum bridges so your selection may be limited.You might want to search for dock and gangway manufacturers, as aluminim has become popular in marine uses. West Coast Flotation Systems and Superior are a couple. (edit - Superior has a price calculator; max. width is 4').

    Some manufacturers of steel bridges are Anderson, Excel, Continental, Big R,

    Some info on composite bridges (FRP) is here.

    Bridge projects are interesting and sometimes challenging. Have fun with it.
    Last edited by radair; 11-02-2008 at 01:18 PM.

  4. #4
    Cleavage Of The Tetons
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    Hmmm...I never thought about using a basic aluminum extension ladder for a platform for a small, elevated treadway over a creek...interesting!

    Think one of these would hold up? (bike only usage, 20' span, wood clamped/bolted on top as the 'tread')

    Just a thought!
    (Edit: with strut supports under the 'ladder stringer' of course, not a straight unsupported span...)
    Last edited by rideit; 11-02-2008 at 11:50 PM.
    "We LOVE cows! They make trails for us.....

    And then we eat them."

  5. #5
    beer thief
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    Quote Originally Posted by rideit
    Hmmm...I never thought about using a basic aluminum extension ladder for a platform for a small, elevated treadway over a creek...interesting!

    Think one of these would hold up? (bike only usage, 20' span, wood clamped/bolted on top as the 'tread')
    I've seen it done by ATVers - they pulled apart an extension ladder (probably stole it first), laid the two pieces side by side, and put planks between the stringers on each ladder. It made for an interesting crossing! First flood washed it away, of course.

    With enough supports it would work. You'd need to keep the span lengths fairly short for it to last, I think.

  6. #6
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    What about using something like a couple or 3 residential floor joists that should be made with exterior type plywood, lumber, and glues for your stringers and deck it with PT lumber. They are pretty light and could always be treated after assembly with a PT stain.

    An aluminum ladder would never span that far and you would be loading it in it's weak axis. For 30 - 40 feet you'd need aluminum or steel I-beams, Glulam type wood beams or trusses, or some pretty big diameter logs or telephone poles. We did a 6 foot wide MTB/Pedestrian bridge with rails and wheelchair curbs that had a 40 foot overall length and free span of about 35 feet to replace one that was hurricane damaged. We replaced 1 existing telephone pole beams with 2 other 18" dia. T poles and it does not budge. We rolled the new TP's across the 2 existing ones with steel pipes short ways and dropped them in next to the remaining TP. The abandoned one eventually gave way after the 2 news ones were set and we decked over the 3 of them with PT 2 X 12's and used 4 X 4 posts bolted through a horiz. 4 X 4 and the posts with 2 X 4 handrails and a 2 X 6 wheel chair curb laid flat inside the posts to keep wheels and knuckles off the rails and posts. Turned out nice! We coated the top sides of the tread lumber with a sand sprinkled paint that's held up nicely for over a year now.

    IMBA has a wood bridge "booklet" on their site.

    See http://www.imba.com/resources/trail_...dgedetails.pdf
    IF YOU CAN READ THIS, YOU'RE NOT RIDING (or building)!

  7. #7
    Wiz
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    ... and if we just ...

    Quote Originally Posted by radair
    I've seen it done by ATVers - they pulled apart an extension ladder (probably stole it first).....

    Oh man, here goes the 1st coffee clean up of the day!

  8. #8
    Masher
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    Here's a very interesting bridge design from common stick-sized lumber...
    http://pacifi.ca/photos.html

  9. #9
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