Wood foot bridge

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Old 07-14-18, 12:40 PM
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Wood foot bridge

I'm contemplating a foot bridge over a creek with three treated 6x6 timbers with four foot 5/4 decking. Will the 6x6 timbers support be stout enough support or will it be to bouncy? The span is 28 feet.
 
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Old 07-14-18, 01:24 PM
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That will be very bouncy.
 
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Old 07-14-18, 02:01 PM
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I agree!! how wide is the creek? feasible to add more supports? you'd also need a 'joist' in the middle.
 
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Old 07-14-18, 02:03 PM
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First, good luck finding 6x6 that long. Second, I would say there is no way 6x6 can simply be lain across to form a bridge even if it were nothing but 6x6 timbers side be side forming a solid 6" thick bridge.

I would start reading up on bridge design. You're going to either need much bigger timbers or you make hand rails that are structural trusses. You can also look for steel beams removed from building or mobile home demolition.
 
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Old 07-14-18, 02:52 PM
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You could limit the bounce by adding a large triangle shaped "guardrail" at midspan and then run a steel cable from end to end, and over the top of the upright. The cable would need some massive turnbuckles and concrete pilings under each end of the bridge... The tension of the cable and fixing the bases of the 6x6s could help counteract the bounce. But yeah, the bridge will be so heavy it needs some sort of engineering... at a minimum with steel cables... the kind/size you see used with highway guardrails.
 
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Old 07-15-18, 11:33 AM
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A "low-water" concrete bridge might work best.
 
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Old 07-15-18, 11:39 AM
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Our creek bridge is 4 2x12x20 and they are solid.

Dont know if you would get much longer unless it was some type of LAM.

You need depth not width for stiffness!
 
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