RSJ size to span 28m footbridge over pond


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Old 04-09-13, 02:50 PM
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RSJ size to span 28m footbridge over pond

Hello, please could one of you clever guys give me some guidance, i need to construct a foot bridge over my pond, 28m x about 1.5m wide (big pond). Id like to use 2x rsj for the main support and build the bridge around these, like an upside down railroad. I can support it with concrete piles but how many would i need and what size rsj. Im looking for the most cost effective way , so the amount of supports against the size of rsj, i am thinking maybe 2 concrete piles per 28m rsj at approx 9m and 18m, i really have no clue or experience in the loading of rsjs.
Any help would be most welcome!
James
 
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Old 04-09-13, 08:25 PM
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I would have an architect design it.
 
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Old 04-09-13, 10:05 PM
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Actually a job for an engineer.

A bridge of that size is in no way a DIY project.
 
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Old 04-10-13, 01:53 AM
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Thanks for your replies , i just really wanted to know what size rsj and how far apart the supports need to be to for the rsj size,to support a few people crossing it. the cladding of the wooden bridge around it is straight forward.
Similar to the loading of a raised deck.
I might even build a rope bridge , so what size of rope?
 
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Old 04-10-13, 02:42 AM
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Just choose a rope that safely supports all loads it will be subject to, plus a safety factor of at least 2.

P.S. You really need to consult an engineer to provide you with an appropriate design. Your local building department will require it.
 
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Old 04-13-13, 04:41 PM
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If you mean rsj, you won't find an rsj to span 18m
This is a DIY site, not a civil engineering site!
 
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Old 04-11-14, 12:39 AM
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You can build your own bridge

but it takes planning and work. We designed and built a 20 meter walking bridge over a seasonal waterway 12 years ago and it continues to perform well. Our bridge uses 6" by 6" wooden vertical support posts that sit on a gravel sub-layer a few feet lower than the waterway soil. The posts (two per support location) are spaced 18 feet apart, looking inline with the bridgeway. Between each opposing pair of posts we lag-bolted 2 by 12s, one each per side of the posts. We then spanned the 18-foot distances with 2" by 12" beams. The beams are then covered with decking made of 2" by 6" planks. All this was done with pressure treated lumber.

I've greatly simplified the total project. If anyone is seriously intent on building a private pedestrian bridge of more than small-pond size, I can mail a copy of our full design plan. I am not an engineer, but if you are willing to study, the mathematics and design calculations are learn-able without an engineering degree.

You should read any applicable local and state regulations. Also, the Forest Service has from time to time published wood bridge designs. These are often for heavier duty and long expected life span. Our bridge cost about $8000 in 2001, including several power tools and a generator to serve its location which has no electrical supply. A fully engineered bridge done by a certified bridge engineer would have been far more costly and, if built by a contractor, costlier still.
 
 

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