Fill tall pole with concrete - cure?

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You were?? Could have fooled me.
Isn't it time we shook hands and moved on? [g]

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In a previous post Glenn wrote...

Okay by me.
I promise not to post any more on this subject.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
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Mike Hammer wrote:

Except that the real issue at hand was stiffness, not strength. That confusion was injected by someone (Nehmo I believe) later in the discussion.
Matt
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The work required to

It probably does for this homeowner.
The poor guy only needed 10' of pipe. The price difference (for a walk in customer) between 3" sch 40 and 3" sch 80 is going to be right around $5.50/foot. So just in material cost he's saved aprox. $55. using sch 40. A couple of bags of concrete or what ever type of mix he used isn't going to be over 7 or 8 bucks.
You have to take into account that there aren't a lot places willing to cut off a 10' piece of pipe for a homeowner. They are out there, but you may have to drive a bit farthur and they will charge you for the cut and likely charge you more on the pipe for buying such a small quantity. It would be similar to going to the lumber yard and asking them to cut 3' off a 8' 2X4, they might do it but they might not.
And if you live in a small town the sch 80 will probably have to be ordered. Try special ordering 10' of pipe. And for the last several years the pipe mills have been working at a pace that means there are times thru the year when a size of pipe is sold out and you have to wait for them to roll that size again.
So I can easily see why a guy would spend the morning in his back yard with a garden hose and a wheelbarrow filling the pipe with (fill in the blank). It makes quite a bit of sense.
And the use of composite columns in small diameter, slender applications is just as well documented as it is in big bore cans.
JTMcC.
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Bill wrote:

Yes, as I mentioned some time back, adding that much mass will make a lot of different in the vibration characteristics.
Matt
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To all:
I know I promised not to write anymore on this subject, but the following message was e-mailed to me and I wanted to share my reply to show that there are indeed practical implications to my earlier posts on this subject.

First, filling an 8-inch sched 40 with concrete may gain you about 30% more stiffness and it will add mass.
An 8-inch sched 80 pipe will give you a 45% increase in stiffness but may not add the mass you desire.
Filling the pipe can be a tedious job depending on the height of the pole. It takes about 0.35 cubic feet of concrete to fill one foot of 8-inch pipe. A typical bag of Quikcrete makes about 0.60 cubic feet of concrete and so will fill slightly less than 2 feet of pipe.
If we say your pipe is 20 feet long it would take about 12 to 13 bags of Quikcrete to fill the pipe. The cost of the Quikcrete material isn't very much, less than $100. Getting that into a 20-foot piece of pipe is not so easy and cheap. You could hire a pump at $300 per day (not very practical). You could hand mix and haul the concrete up a tall ladder and pour it down the pipe. Possible, but a lot of work. Not to mention that the concrete is now dropping 20 feet and will segregate (not a good thing).
Or you could do what I have been recommending in alt.building.construction, which is pay for a larger diameter or thicker wall pipe and leave it empty. A lot less work to accomplish the same thing.
Now, if you had a large number of these pipes in a solar array of some sort, then it might make some economic sense to buy the thinner wall pipe and use equipment to fill them with concrete. But, I just don't see this as being practical for a "one of" scenario.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
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I'm surprised no one mentioned guy wires - pretty much industry standard for aerial towers, right? If you're trying to eliminate swaying, that's the surest way to achieve that end. Anything else is adding weight and strength where you don't need it and the pipe will still sway.
R
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