tapered concrete pillars

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Our late '40s place has concrete pillars in the basement - about 7' high, 12"x12", but tapered in toward the top by maybe 2". Fair enough... but I just noticed that they're also tapered by 2" at the bottom, albeit just in one axis (I've never noticed before as they've had junk piled around them - I've just been having a tidy-up though)
Any particular reason for the tapering at the base? I don't think I've ever seen that before, and can't think of a good reason for it.
cheers
Jules
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On Tue, 08 Dec 2009 15:13:12 -0600, Jules

Donno. Crane booms have a taper a both ends.* I imagine the strength is in the middle?
http://www.craneweb.com/files/imagecache/crane_full/node/add/crane/8659233.jpg
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Oren wrote:

Probably was a 2-piece metal mold- fill the bottom, stick in the rebar, put the top on, and finish filling. They didn't have sonotube back then, and getting stuff out of an eight-foot mold is a pain. Is there evidence of any sort of ground-down 'mold flash' line at the mid-point?
Musta been built during war when steel was in short supply or something. I've probably been in over 1000 basements over the years, and I have never seen formed concrete basement pillars before. Either steel or wood or laid-up brick columns.
-- aem sends...
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wrote:

Pics would help, being, it is "late '40s place has concrete pillars in the basement "
I'm interested.
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On Tue, 08 Dec 2009 15:54:29 -0800, Oren wrote:

Sure, quick one at:
http://www.patooie.com/temp/pillar.jpg
cheers
Jules
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On Wed, 09 Dec 2009 09:28:56 -0600, Jules

Are you certain they are solid concrete and not maybe brick columns that have been finished over?
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On Wed, 09 Dec 2009 10:40:02 -0500, salty wrote:

Hmm, no I'm not actually! Maybe next time I'm using an SDS down there I'll drill a little core sample just to make sure. Looking at the tops in the little dip where the wooden beams sit, there's no evidence of it being anything other than concrete (so if they clad them in concrete they did it before all the lumber went in). I still can't imagine a good reason for the bottom taper, either, even if they do have a brick core.
(there's a chance I can ask sometime; the grandson of the people who built the house has a cabin in the fields behind our place, and I think his father - who would have been a young boy when the house was put up - is still around. It's possible someone might have told him the reason and he might have remembered it. The cabin's all shut up for the winter right now though, so that'll have to wait until next spring before I can ask!)
cheers
Jules
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On Dec 9, 10:40am, snipped-for-privacy@dog.com wrote:

Is that just a pile of bricks in the photo or the remains of an old brick column? Maybe there were brick columns which started to fail at some point and were replaced with something they felt would last?
When you first described them, I also considered that maybe the mold just wasn't strong enough and bulged, but seeing the photo, that doesn't look like the case. Now I'm leaning towards someone just wanting them to look interesting.
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On Wed, 09 Dec 2009 09:43:39 -0800, Larry Fishel wrote:

No, just a pile of bricks - they were originally part of a huge enclosure built around that (home-made) wood furnace that you can see lurking just behind the pillar in the photo. I salvaged them, figuring I'd probably make some pillars at the end of the driveway with them one day, but they've not quite made it out of the basement yet ;-)

Yeah, it certainly looks intentional to me; the curve seems to follow the same line on both sides and is also mirrored at the top.
There's what's either an ancient capped septic system or capped well in that part of the basement, though, and as far as I can tell the wood chute was always in that part, and the access to the basement is way over on the other side... in other words it's a funny part of the house to be just making things look nice - but anything's possible!
cheers
Jules
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These are not gently tapered concrete columns. This is form work that was underdesigned. The liquid head putting pressure at the bottom of the form is huge. I am almost surprised that the forms didn't blow open during the pour, but then we can't see the original form work.
Nothing fancy, not deliberate - just lucky.
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On Thu, 10 Dec 2009 05:08:28 -0600, DanG wrote:

I don't know - I just did a check with straight-edge and ruler, and the lower tapers start 16" above the floor. The upper tapers start 16" below the top. They taper by the same amount and at the same point on both pillars that I looked at. The amount of tapering is even on both sides (and only in one axis, of course).
Like you say, we've no idea what the original form was like; I can see how that could explain the tapering in only one axis if the sides were strong but the front/back not so.
I don't know enough about concrete to say if a weak form like that would yield exactly the same taper front and back at the bottom, and on more than one pillar if the form design were re-used.
The fact that it's the same curve top/bottom, starting from the same point relative to the mid-point, and that it's dead-straight across the center portion gets me, though - that makes it 'feel' more intentional, as though whoever made them wanted them that way.
cheers
Jules
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On Tue, 08 Dec 2009 18:36:10 -0500, aemeijers wrote:

No, nothing at mid-point. Various vertical casting lines though, which suggests to me that they made a mold from wooden strips.
I just did some proper measuring too (that'll teach me to take a quick look and then post in a hurry!) and they're actually 12"x16", and 11"x16" at the top and bottom (so not 12x12 square like I said in the OP, and the tapering's less pronounced than it looks to the eye)
I took a quick photo - see reply to Oren...

Yeah, the guy who did the home inspection when we bought the place said he'd never seen ones like that before.
Lots of the construction around this area was done by the family who previously owned our place though, and it appears they were happy to work with whatever materials they had (our barn's rather oddball in its construction, too). Makes me wonder if they just happened to know someone who could supply concrete, or someone owed them a favor, so they did that rather than using wood or metal.
12"x16" seems overkill, though. The basement walls are all poured concrete too, 10"-12" thick; it's pretty solid down there.
One other possibility is that the pillars weren't cast in-place, but were brought in from somewhere else and were maybe originally intended for some other construction project. I still can't think of a good reason why they'd need to be narrower at the bottom, though (I mean, if they had to sit on something that was 11"x16", then why not just make them 11"x16" all the way up...)
cheers
Jules
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On Wed, 09 Dec 2009 09:40:51 -0600, Jules

Maybe the forms were not quite strong enough and simply bowed out from the weight of all that concrete?
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On Wed, 09 Dec 2009 10:53:10 -0500, salty wrote:

Hmm, interesting idea! If that were the case then it seems a little odd that they'd only tapered in one axis, not both - but then I suppose there's no way of knowing what the form looked like....
My gut feeling is still that it was intentional - although I keep wondering if whoever made the molds had simply drunk a little too much beer the night before and ended up engineering a taper at the bottom as well as the top :-)
cheers
Jules
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On Wed, 09 Dec 2009 09:57:22 -0600, Jules

If it was me-- that would've been the side I thought I could get away with 1/2 plywood on-- and then the nails pulled through.

Or perhaps they just had a bit of brandy & got to thinkin' . . . "What can I do to those columns tomorrow to befuddle everyone who looks at them over the next couple centuries?"
Jim
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Jim Elbrecht wrote:

Snort! I like it.
I think you are right, they look precast, and maybe were for another application. I dunno- maybe bridge rail columns designed to drop into precast pockets on something. Any RR yards around there? Maybe they were liberated from some roadbed repair stock- those almost look like what I see along side the rails at a siding switch.
-- aem sends...
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On Wed, 09 Dec 2009 18:33:17 -0500, aemeijers wrote:

The pockets idea makes sense if they were intended for some application where they could be replaced, but does (or did) anyone really do construction like that? I suspect there'd be significant wear around the top of the pocket from vibration etc. if it were a bridge environment (rail or otherwise).
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Jules
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That's because crane booms (usually) have to pivot, and have zero sheer force on them.
For the pillars, my first guess would be sloppy forms. My second guess would be aesthetics. I can't think of a functional reason (but that doesn't mean here isn't one).
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Larry Fishel wrote:

I'd wager it was combination of aesthetics and ease of pour that controlled.
There is a larger bending moment at the middle that could be argued to be related but imo the likelihood of there being enough load in a residence for there to be any need whatsoever for a 12" section at the middle unless these are extremely tall for a basement would be approaching nil...
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Of course, I didn't really mean shear (or sheer) force. More like a bending/torquing force (and of course there is some in the middle of the span due to the weight of the boom itself).
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