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built up wood tension members
- Thread starter rittz
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Hi TLHS This for the response
Are you saying that if we build a 2-ply long built-up tension member by half lapping 16 ft. lengths (8’) of 2 x 6 that the useful section for tension would be 3” x 5 ½”. I feel it would be true of a section for compression (axial load), but it seems counterintuitive for tension??
BTW the fasteners I would visualize as bolts or spikes from ply to ply
Are you saying that if we build a 2-ply long built-up tension member by half lapping 16 ft. lengths (8’) of 2 x 6 that the useful section for tension would be 3” x 5 ½”. I feel it would be true of a section for compression (axial load), but it seems counterintuitive for tension??
BTW the fasteners I would visualize as bolts or spikes from ply to ply
Hi rittz,
I don't think that is what tlhs is saying. The terminology is very loose, (" 2 or 3 ply built-up timber strut" & "2-ply long built-up tension member by half lapping 16 ft. lengths (8’) of 2 x 6 "), admits more than one interpretation, and the interpretation I would guess for you second post leaves an available cross section of a single 2x6 less the proper allowance for fasteners as queried by focuseng.
I'd suggest you draw a sketch of what you're thinking, and I'm sure you'll obtain a crystal clear and correct response within hours.
Good luck!
I don't think that is what tlhs is saying. The terminology is very loose, (" 2 or 3 ply built-up timber strut" & "2-ply long built-up tension member by half lapping 16 ft. lengths (8’) of 2 x 6 "), admits more than one interpretation, and the interpretation I would guess for you second post leaves an available cross section of a single 2x6 less the proper allowance for fasteners as queried by focuseng.
I'd suggest you draw a sketch of what you're thinking, and I'm sure you'll obtain a crystal clear and correct response within hours.
Good luck!
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- #6
Perfect,
What I believe was your intuition in your previous post is correct. You get, at absolute maximum, the tension value of a single 2x8 in this case, knots and all. Your system's tension value will depend upon the fasteners used and their locations as well as the wood quality. I generally prefer nails which part the wood grain in these connections, others will prefer bolts which actually remove wood material. Your engineer will look for the "weakest link", which maybe the single 2x8, or the effective net section with bolt hole material removed which depends on locations of bolts, or the fasteners themselves and their various modes of failure. The code gives explicit guidance on fastener locations and calculations.
What I believe was your intuition in your previous post is correct. You get, at absolute maximum, the tension value of a single 2x8 in this case, knots and all. Your system's tension value will depend upon the fasteners used and their locations as well as the wood quality. I generally prefer nails which part the wood grain in these connections, others will prefer bolts which actually remove wood material. Your engineer will look for the "weakest link", which maybe the single 2x8, or the effective net section with bolt hole material removed which depends on locations of bolts, or the fasteners themselves and their various modes of failure. The code gives explicit guidance on fastener locations and calculations.
MikeHalloran
Mechanical
As BA says, you're wasting almost half the wood.
If you get wood cheap, or labor and skill is expensive, that's okay.
If you were building a boat, you'd probably use a scarf joint and a good adhesive to develop the full cross section of the wood, but that is a little skill-intensive.
Mike Halloran
Pembroke Pines, FL, USA
If you get wood cheap, or labor and skill is expensive, that's okay.
If you were building a boat, you'd probably use a scarf joint and a good adhesive to develop the full cross section of the wood, but that is a little skill-intensive.
Mike Halloran
Pembroke Pines, FL, USA
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