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kebwi 07-12-2012 12:15 AM

Steel pipe vs. rebar-concrete-filled-PVC for a column
 
To make a short sturdy column, embedded about three feet deep and extending three to five feet above ground, and of diameter approximately three to four inches (to be a "foot" over which to slide the end of a tall vertical pole) one might conventionally use a piece of steel pipe...but I think that's expensive and troublingly difficult to source.

Another way is to use a PVC pipe, drop a bunch of rebar in it, and fill the whole thing with concrete.

Such pipes are common in other uses (telescope pier mounts for example). Non PVC concrete pillars are, of course, a basic staple of construction, but those primarily bear a vertical load whereas the purpose of the column in my application is to provide lateral resistence to a "balancy" vertical pole (plus additional lateral forces, see other thread for more on that). An all-concrete column would obviously be a bad candidate for a "sideways-pushing" (lateral) requirement since it could simply break...but with the flexible yet strong PVC holding it all in place and with sufficient rebar to skeletonize the whole thing, I think it has potential.

Do you think this would work? Would it adequately support a vertical pole in the same basic fashion as a steel pipe? If so, how would you trade off the amount of rebar vs. the amount of concrete?...or would you never in a million years go near this insane idea?

metalmaster 07-12-2012 02:50 AM

Re: Steel pipe vs. rebar-concrete-filled-PVC for a column
 
I would go with the steel pipe, the concrete will want to break away from the rebar when it flexes, and the pvc gets brittle over time.

you should be able to source a short piece of pipe without to much trouble


mike

kebwi 07-12-2012 07:16 AM

Re: Steel pipe vs. rebar-concrete-filled-PVC for a column
 
Yeah, for $100. Dammit.

Okay, thanks.

Tscarborough 07-12-2012 07:24 AM

Re: Steel pipe vs. rebar-concrete-filled-PVC for a column
 
A fence post shouldn't cost a hundred bucks. Buy the thin gauge fence post and fill IT with concrete (no rebar needed).

kebwi 07-12-2012 08:14 AM

Re: Steel pipe vs. rebar-concrete-filled-PVC for a column
 
Thanks Tscarborough.

deejayoh 07-12-2012 03:36 PM

Re: Steel pipe vs. rebar-concrete-filled-PVC for a column
 
I've got some cyclone fencing I need to cut down. You can have a post :)

kebwi 07-14-2012 11:33 PM

Re: Steel pipe vs. rebar-concrete-filled-PVC for a column
 
So, the primary pole is about 3-1/2" inner diameter at the bottom and I will slide that over anchor pole a few feet high (embedded in concrete). I got some thin-walled (1/16") fencing conduit 2-3/8" wide, which is about as wide as can be easily found. If I slide the primary pole over that, it's going to have a lot of freedom to flop around. I think I should "thicken" the inner pole somehow. Not to mention, if I place something nonmetalic between the two poles they won't clank too loudly. A piece of 3" PVC is 3-1/2" outer diameter, which is perfect to fit inside the primary pole, but it's still too lose relative to the inner pole (2-3/8").

What would you do about this? How would you tighten up this gap so the two poles fit together more snuggly?

Tscarborough 07-15-2012 06:48 AM

Re: Steel pipe vs. rebar-concrete-filled-PVC for a column
 
Have you ever used a cheap Christmas tree stand?

kebwi 07-15-2012 08:23 AM

Re: Steel pipe vs. rebar-concrete-filled-PVC for a column
 
Hmmm, the kind I'm familiar with puts screws through the stand to touch the (and even penetrate) the tree. I was hoping not to drill holes in the nice aluminum pole. When we all discussed this method of anchoring the primary pole by sliding over a shorter thinner pole, was that the intention all along? --that I would bolt through both poles? I could do that, I just hate to ruin a nice pole. :-)

Was that the idea?

I guess I could just place some bolts through the inner pole which achieve an "outer diameter" of the inner diameter of the outer pole.

Tscarborough 07-15-2012 09:06 AM

Re: Steel pipe vs. rebar-concrete-filled-PVC for a column
 
You just need one, and you could do it low if you like, although you will get more noise if you do so.


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