I ran into one issue on pvc pipe, the largest the plumbing supply had was 10" and several piling butts exceed that. In addition one length of 10" was >$250. Couplings were >$50 would guess end caps would be comparable. That comes to over $100 per 6' piling and I am doing 13.
Additional research indicates that fiberglass reinforced plastic has a tensile strength of 20,000 pounds per square inch. A few wraps of fiberglass cloth tape around the joint with epoxy should have the joint exceed the strength of the piling.
I think that will work best for me.
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Re: Piling extensions over or under engineered
Regards,
Vincent Castigliola
Lilly Marie - 43 DC 1983
Pascagoula, Mississippi
Rather than history as a peaceful continuum interrupted by war, “For the first time in the nation's history men in authority are talking about an "emergency" without a foreseeable end" _ C. Wright Mills 1956
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03-25-2010 08:41 PM #12
Re: Piling extensions over or under engineered
Gee Vincent, I have seen PVC pipe being used for city water mains. This stuff was big enough to crawl through. That price is hard to handle for sure.
Maynard
UNITY '86 36C
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03-26-2010 12:24 AM #13Senior Member
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Re: Piling extensions over or under engineered
Vincent: In several of your posts you're using the term "tensil strenght" of rebar or epoxy as an indication of the strength of the proposed joint. The problem is your piling joint will be subjected to shear (pounds/sq.in.) and bending (ft-lbs) forces and not tensil forces, generated by the boat impacting the piling. Impact forces are quite different than static forces. Impact forces generate much higher stresses than the equivelant static forces. Driviving a nail with a hummer into a wood block is much easier than driving the same nail by just pushing it down even with a static force 2 or 3 times greater than that generated by the hummer impacting the nail. So, in order to understand how a structural joint will behave, under load, you first have to have a good undestanding of the type of forces acting on that joint. The tensil strength of the joint is normally associated with a force acting along the long axis of the pile or rebar putting either one in tension until it fails (breaks).
Now I'm wondering why the hell I wrote what I wrote above. Does it serve any purpose? Well take it for what is worth, which maybe not much.
CapetaniosG
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03-26-2010 04:19 AM #14Senior Member
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Re: Piling extensions over or under engineered
The problem I see with the original design is when your boat rub rail pushes on the pile far away from the joint. This will result in a very strong moment at the joint which will cause it to "pivot" on one side and pull the rebar out of the join OR will just bend the rebar.
Rebar is designed to be strong in tension only. If you can somehow be sure the rebar is bonded to the wood and won't release, then when a moment (push on the top of pile) is applied, the rebar will only be loaded in tension.
Shear loading will occur if your boat contacts the piling very near the joint....but I wouldn't worry about this scenario as I do not think it will cause failure.
One option I can think of that would address the above loading problems would be to bore out the center of the pile on the top and the bottom for a 4x4 or something similar. Then you can through bolt through the piling and the 4x4 on both the top and the bottom (and countersink). A large dowel would work too.
Another option is to just use doweling and then use strapping on the outside of the pile running from the top to the bottom. The strapping will take the tension and the dowel will take the shear---and the combination of the two will solve the moment problem.
And even another option is to drill continuous holes vertically in both the top and the bottom and use all thread. Drill near the circumference to allow for cutting a notch out to on put in a plate/washer and a nut. This will satisfy the loading the same way as the dowel and straps.
But really, I think ya'll should just debate shadow ghost forces and loadings on the internet LOL. Whatever you do, good luck.
Disclaimer: no expertize was used in making the above post. Everything I know I learned from Wikipedia.org. My comments are worth exactly what you paid for them.
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03-26-2010 08:20 AM #15Senior Member
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Re: Piling extensions over or under engineered
Vincent,
You have created a " hinge " connection. Setting a sister pile
along the existing pile is the best solution. An alternate would
be the splint idea with 2"x material attached to the side as mentioned
earlier. A 3' extension will require a 6' overlap to offset the cantalever.
That's your 2 cent consultation from a humble Architect.
Mike
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03-26-2010 08:54 AM #16
Re: Piling extensions over or under engineered
Looking for another boat...not a Hatt
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03-26-2010 08:56 AM #17
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03-26-2010 09:26 AM #18Senior Member
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Re: Piling extensions over or under engineered
That SURE is a great tree....reminds me................................................ ..............damn, can't remember now....Oh well, never mind...
"Additional research indicates that fiberglass reinforced plastic has a tensile strength of 20,000 pounds per square inch. A few wraps of fiberglass cloth tape around the joint with epoxy should have the joint exceed the strength of the piling."
I think post #13 covers it....you CANNOT count on a few fiberglass wraps to hold your boat in high winds....just not gonna work....use bolts and lumber as described above....maybe copy proven pile extensions in use in your area if you can find any examples....Rob Brueckner
former 1972 48ft YF, 'Lazy Days'
Boating isn't a matter of life and death: it's more important than that.
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03-26-2010 09:57 PM #19
Re: Piling extensions over or under engineered
WOW..You guys are over-engineering the daylights out of this simple and very crude job.
Maynard
UNITY '86 36C
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Re: Piling extensions over or under engineered
Crude,
Maynard, now I feel insulted, but you did answer the question. It is over engineered. But considering Krush's disclaimers. . .
This probably is Chevy rather than Jaguar engineering ( See Richard Prior's answer to Gene Wilder in SILVER STREAK ) I appreciate all the analysis and it has led me to further thought and a final solution.
A 10" x 3/4" hole was drilled in the center at one end of each piling. 10" of a 20" #5 rebar was embedded in the top piece and glued in place with filled epoxy resin. After set up, the extension piling was placed on top of the base piling with the other 10" of the rebar embedded and glued into the base piling hole. The top and hole in the base piling was coated/filled with more filled epoxy. The joint is then wrapped with 3 layers of fiberglass tape and epoxy.
As shown in the diagram below, the joint is a composite structure. When force is applied to one side of the extension, the rebar (Green) is placed in tension and one side of the piling joint fiberglass cloth (Purple) is in tension and the other compression. Everything is attached to the piling with epoxy (Red) including the rebar. As I understand it, builders secure rebar and bolts into existing concrete slabs with epoxy and the joint is stronger than the rebar. Wouldn't wood be the same, yielding a joint as strong as the weaker of either the rebar or the piling?Regards,
Vincent Castigliola
Lilly Marie - 43 DC 1983
Pascagoula, Mississippi
Rather than history as a peaceful continuum interrupted by war, “For the first time in the nation's history men in authority are talking about an "emergency" without a foreseeable end" _ C. Wright Mills 1956