Fill tall pole with concrete - cure?

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I don't think so. When you get that 12' wire mesh dish installed that pipe will sway all over the place in the slightest breeze. You'll be able to move it with a touch of your finger. I thought you were using steel pipe. I'm sorry to say but you've wasted your time.
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In a previous post Bill wrote...

As expected by those of us with technical backgrounds. You have changed the mass of the pole and thus have changed its natural frequency of vibration. You have not changed the strength of the pole appreciably, but have substantially changed the force it takes to get it vibrate. Those are not the same thing.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
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Wow, I didn't read every word but the use of concrete/steel composite structural elements (usually as a pile or a column) has been pretty well documented for decades. Concrete filled pipe or tube is substantially stronger than when empty, you don't have to guess at it the research has been ongoing for quite some time. I'd guess that anyone with an internet connection and a few minutes could dredge up some numbers, if not, they could definitly find WHERE to get those numbers. I would give a couple of references, but that would be too easy. Structural engineers should know these things in my opinion.
JTMcC.
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In a previous post JTMcC wrote...

The whole subject has gotten out of hand. Concrete filled pipes can be a good idea when used in the proper location. But, there is a world of difference between a large diameter concrete filled pipe pile and a small diameter pipe post. Many posts under this subject have confused strength with stiffness, and strength with resistance to vibration. It is the resistance to vibration that was the subject of the original post. Filling a pipe with concrete will change the mass and will change the natural period of vibration. Buying a thicker walled pipe will do the same thing and be a lot easier that trying to pour concrete down a 3-inch pipe.
Some posters on this subject have said things like, "If I bang on a concrete pipe filled with concrete it won't dent, and thus must be stronger." Sure, it won't dent. But the bending stiffness when acting as a cantilever column of a small diameter pipe is not appreciably changed by the addition of the concrete. It will still vibrate, just not with as much magnitude because it takes a higher force to move the larger mass the same distance.
My point all along has been that in this instance buying a larger diameter or thicker walled pipe is more cost effective than trying to fill a small diameter pipe with concrete, I.e., if you value your time. Maybe for some it is a wonderful Zen exercise to put concrete in a small hole and tamp it down to the bottom. That's okay by me. Just don't expect miracles.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
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says...

Generally, a steel pipe filled with concrete will have almost twice the bending strength as the same pipe with no concrete. If that is not enough increase in strength for your purposes then you must go with a larger pipe. Of course that pipe can then be filled with concrete to double ITS strength.<grin> Filling a pipe with concrete will always increase its strength but you have to match the pipe size to the application.
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Bob Morrison wrote:

Yes, and the latter has the advantage of dramatically increasing stiffness and strength as well as changing the natural frequency.
Matt
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Out of hand???? Interweb police have maybe shown up? From your posts here I have to think that you have no experience with concrete filled columns or piling, of any diameter, or you wouldn't of posted some of the comments you've made. The gains to be made by filling a tube or pipe are out there for most to view, including you. I'm not a SE but I have them on the payroll from time to time, and we deal with concrete (or grout) filled tubes and pipes from time to time and you are disregarding a substantial gain that this guy can attain with little time/money/effort. Do everyone a favor and do the research, I certainly have, and quit trying to defend a somewhat indefensible position.
JTMcC.
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JTMcC wrote:

If you have done the research, post one source here that shows the stiffness gain from filling a tall, skinny pipe with concrete.
Matt
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In a previous post Matt Whiting wrote...

MY SENTIMENTS EXACTLY!
(and yes I meant to shout!)
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
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I have quite a bit to get done this week, I certainly don't have the time you do to spend chatting on usenet. So I don't intend to do your homework for you.
I'll leave these thoughts as my last comment on your little arguement.
I'm guessing those recomending heavy wall pipe as a solution have not tried buying pipe in todays marketplace, and probably haven't priced or checked availability, and certainly not in the incredibly small length this guy needs for his dish.
JTMcC
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JTMcC wrote:

I wouldn't recommend a trip to Vegas as your bluffing technique needs some work.
Matt
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I spend well over 100 days a year in Las Vegas many years. We generate a considerable amount of income in Clark County.
You appear to be well out of your area of expertise and you most definitly have little or no practical experience in the area. It's a common flaw in cyberengineers to portray themselfs as experts on each and every topic that comes up. I'm guessing you are there in a big way.
I'd be curious to see just how many posts you have here in cybertude. How, and when, do you actually work??? Or do you work?? Doing what? Engineering "housing"? LOL.
JTMcC.
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JTMcC wrote:

Having one's bluff called is so embarrassing. When you can't provide the data you have to resort to insults. How sad...
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You probably have the capability, and the time, to do a search on the topic if you don't have the appropriate reference material on hand. I'm running a business and I'm certainly not going to do the search for you, or dig thru the tons (literally) of material here to find information on composite concrete filled tubes/pipes in both big bore and small/slender applications. I have little mouths to feed. Now, if that's what you call embarassing and sad, then you my little man have an embarassing and sad internet existence. To me a sick child is sad, a young Mother dying, ect. And as for embarassing, well I'm pretty imune to that so I can't help you there, but to use those words in the context of a discussion on usenet means you are just a little bit to heavily invested in your cyber identity. Others have probably told you this already. My advise is to turn the computer off every once in a while., get outside in the fresh air, and actually do something. Drive around. You'll feel better. Your world won't revolve around a computer screen. Don't worry, that guys shingles will still get nailed down, roofs have been replaced for thousands of years without you. Maybe you could put a dish up in your backyard for a little outside project? You could use some sch. 160 pipe! Or 3" cold rolled round stock.
JTMcC.
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Is there a lot of money in telling a guy (on the net) how to nail his shingles to the roof of his house? lol, now THAT'S engineering, cutting edge I might add, you should author a paper: ) Thank goodness you're here! Those home owner do it yourselfers might cause the collapse of the worlds infrastructure.
JTMcC ; )

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In a previous post JTMcC wrote...

Once again you have missed my point. Filling large diameter pipes can have some beneficial effects for the cost involved. The work required to fill a small diameter pipe (we are talking 3" diameter here) does not provide sufficient beneficial effect to warrant the extra work required.
And yes I have often dealt with large diameter pipe piles and have chosen not to fill them with concrete because the minor gain in stiffness did not warrant the extra cost. If your SE's are recommending concrete filled tubes then I suggest you have them demonstrate the cost benefits of doing so as compared to simply using a larger diameter or thicker wall.
Many of you seem to think I'm an idiot. That's okay. I know what I know and anything you may say can't change the physics. So, if you have a real argument that can be backed by real numbers then let me see it.
I will even propose a problem to be solved:
A 3-inch x 0.120" wall pipe. Pipe is 3" OD. Install a 24-inch diameter dish antenna at the top of 12 feet of pole. Apply a 10 psf wind load to the dish (you may ignore the wind pressure on the pole). Compute the deflection at the top of the pole with the pipe empty and with the pipe filled with concrete. Now increase the wall thickness to 0.250" and compute the deflection at the top of the pole. Tell me which pole deflects the least. For simplicity you may assume that the pole is fixed at the ground line (not really true, but for this exercise we will assume it to be so.)
Localized buckling of the pole need not be considered for this exercise although with a 0.120" wall and 12 feet of height this is certainly a consideration for the unfilled condition.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
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says...

You're talking economics here.

Do a Google search and you will see that this is being done in bridge and other construction because it is CHEAPER. Concrete is cheaper than steel. If you chose not to increase the strength of your pilings then that was an economical decision - not a structural decision.

If many think you're an idiot then perhaps YOU should come up with the real numbers. You can do a simple Google search and discover that pipe filled with concrete nearly doubles its strength. The argument about the diameter or length of the pipe is ludicrous. Adding concrete only doubles the strength - it is not a substitute for using the correct diameter/length of pipe for the application.
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In a previous post Mike Hammer wrote...

Mike:
You are mixing apples and oranges. Filling large diameter pipes used in bridges and other construction is different than filling small diameter pipes used for a TV dish. On a large scale project with large diameter pipe, filling them with concrete can make sense depending on the application. However, all too often it is being done simply because, "We've always done it that way." And, not because someone has actually studies whether or not it makes economic and engineering sense to do so.
Try working the problem I posed. You will find that an unfilled 3-inch OD pipe with 0.25" wall is stiffer than a 3-inch OD pipe, 0.120" wall filled with concrete. It's that simple.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
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says...

OK. If that is all you were trying to say then I agree with you. I was thinking that someone said that adding concrete does not increase the stiffness/strength of a pipe. It may not increase it enough for a particular application but it does increase it.
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In a previous post Mike Hammer wrote...

Exactly! That's all I've been trying to say.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
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