Fill tall pole with concrete - cure?
Bill
(sand/topping mix). It took one and a half bags to fill the pipe.
I am doing this for a satellite dish antenna so the pole will be more stable
and not "wiggle".
Basketball mounting poles also have this done I am told....
Question: All that concrete is basically enclosed in the pipe and there is
just the opening at the top. How would the concrete cure? How long would it
take to cure? (Just curious...)
Bob Morrison
First of all I doubt that filling the pipe with concrete will have much
affect on the overall stiffness of the pole. The mount to the ground is
the most critical element.
The concrete will harden just fine. It's a chemical reaction taking
place, not drying in the typical sense. Remember concrete will set up
underwater if need be.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA
bob at rlmorrisonengr dot com
PeterD
wrote:
>In a previous post Bill wrote...
>> I have a 10 ft. high 3 inch diameter pole which I filled with concrete
>> (sand/topping mix). It took one and a half bags to fill the pipe.
>>
>> I am doing this for a satellite dish antenna so the pole will be more stable
>> and not "wiggle".
>>
>> Basketball mounting poles also have this done I am told....
>>
>> Question: All that concrete is basically enclosed in the pipe and there is
>> just the opening at the top. How would the concrete cure? How long would it
>> take to cure? (Just curious...)
>>
>
>First of all I doubt that filling the pipe with concrete will have much
>affect on the overall stiffness of the pole. The mount to the ground is
>the most critical element.
Having done a lot of these (for satellite dishes, no less) yes, it
does make a difference. Not to understate the need for a really good
base.
>
>The concrete will harden just fine. It's a chemical reaction taking
>place, not drying in the typical sense. Remember concrete will set up
>underwater if need be.
IMHO it will setup better in the pipe as it won't dry. Drying cement
won't cure properly anyway.
Glenn
because of the heat buildup. When that section was set, they
pumped the pipe full of concrete and sealed it so sure it will set
up. And yes it will be stiffer. For a pipe to bend, a wall has
to collapse a fraction to full collapse. Full of concrete, that
action is curtailed.
"PeterD" <pet...@hipson.net> wrote in message
news:c19v239eu2kkb9lq6...@4ax.com...
Nehmo Sergheyev
> First of all I doubt that filling the pipe with concrete will have much
> affect on the overall stiffness of the pole.
Er... Bob, OP is referring to the construction material, concrete. You
must have misunderstood, and somehow you went off talking about about
your experience with Viagra.
--
(||) Nehmo (||)
Bob Morrison
> > First of all I doubt that filling the pipe with concrete will have much
> > affect on the overall stiffness of the pole.
>
> Er... Bob, OP is referring to the construction material, concrete. You
> must have misunderstood, and somehow you went off talking about about
> your experience with Viagra.
>
A properly sized pole will be as stiff as it needs to be to get the job
done.
No Spam
I think the concrete stiffens the pole to better dampen out the
vibrations that can occur when the ball hits the rim. Also, alot of the
basketball pipes are multiple sections, so the concrete helps it act
like one structure instead of 3 pieces of pipe. I think the concrete is
a good idea for a satellite mount, as the wind can cause similar
vibrations and bending. I think you did good.
tmu...@juno.com
To answer your question, It will take 28 days to reach full strength
but just a few to hit 75%
Matt Whiting
I suspect it is more an issue of adding mass to the pole to change its
resonant frequency than it is of adding stiffness.
Matt
PeterD
wrote:
IMHO, the response that alluded to the pole's mode of failure
(collapse) being blocked by the cement is more the factor, but I'm
sure resonence is a factor too.
Bob Morrison
> >> I think the concrete stiffens the pole to better dampen out the
> >> vibrations that can occur when the ball hits the rim. Also, alot of the
> >> basketball pipes are multiple sections, so the concrete helps it act
> >> like one structure instead of 3 pieces of pipe. I think the concrete is
> >> a good idea for a satellite mount, as the wind can cause similar
> >> vibrations and bending. I think you did good.
> >
> >I suspect it is more an issue of adding mass to the pole to change its
> >resonant frequency than it is of adding stiffness.
> >
> >Matt
>
> IMHO, the response that alluded to the pole's mode of failure
> (collapse) being blocked by the cement is more the factor, but I'm
> sure resonence is a factor too.
>
Pouring concrete into a small diameter post seems a waste of effort to me.
It's a heck of a lot easier to just get a bigger pole.
Michael Bulatovich
"Bob Morrison" <SpamF...@junk.com> wrote in message
news:MPG.209bc29e1...@news.west.earthlink.net...
> In a previous post PeterD wrote...
>> >> I think the concrete stiffens the pole to better dampen out the
>> >> vibrations that can occur when the ball hits the rim. Also, alot of
>> >> the
>> >> basketball pipes are multiple sections, so the concrete helps it act
>> >> like one structure instead of 3 pieces of pipe. I think the concrete
>> >> is
>> >> a good idea for a satellite mount, as the wind can cause similar
>> >> vibrations and bending. I think you did good.
>> >
>> >I suspect it is more an issue of adding mass to the pole to change its
>> >resonant frequency than it is of adding stiffness.
>> >
>> >Matt
>>
>> IMHO, the response that alluded to the pole's mode of failure
>> (collapse) being blocked by the cement is more the factor, but I'm
>> sure resonence is a factor too.
>>
>
> Pouring concrete into a small diameter post seems a waste of effort to me.
> It's a heck of a lot easier to just get a bigger pole.
You've been reading that spam again, Bob.
Mike Hammer
Several years ago I filled a basketball pole with concrete. I put a 5/8" rebar
down the center and then poured in the concrete. It was an improvement but it
didn't make it as strong as I had imagined that it would.
Concrete cures by chemical reaction so it doesn't matter if the mix is inside a
pipe or under water - it will still cure.
Nehmo Sergheyev
> Pouring concrete into a small diameter post seems a waste of effort to me.
> It's a heck of a lot easier to just get a bigger pole.
Why don't you just admit you weren't thinking when you wrote your
post, and move on. Lots of times I write stupid stuff too. Well, I'm
afraid I don't write things *that* stupid, but you get the idea. If
you try to defend a untenable position, it just gets worse.
It's really hard for me to understand how you could have said, "I
doubt that filling the pipe with concrete will have much affect on the
overall stiffness of the pole."
_Are you still standing by that statement?_
A pipe filled with concrete, a 3" pipe for this example, is much
stronger (and stiffer, if that's the term we want to use). Think about
it. For a pipe to fail, it has to deform. It can't deform easily if
it's filled with concrete. It's hard even to dent such a pipe with a
sledge hammer.
I could excuse you for not having experience with pipes filled with
concrete. But, considering you write "PE, SE" whenever you write your
name, and you advocate getting an engineer for almost everything, I
can't excuse you for missing the mechanics of how concrete would make
a pole stronger (or stiffer). In short, you're asking for it.
Bob Morrison
>
> A pipe filled with concrete, a 3" pipe for this example, is much
> stronger (and stiffer, if that's the term we want to use). Think about
> it. For a pipe to fail, it has to deform. It can't deform easily if
> it's filled with concrete. It's hard even to dent such a pipe with a
> sledge hammer.
>
> I could excuse you for not having experience with pipes filled with
> concrete. But, considering you write "PE, SE" whenever you write your
> name, and you advocate getting an engineer for almost everything, I
> can't excuse you for missing the mechanics of how concrete would make
> a pole stronger (or stiffer). In short, you're asking for it.
>
Yes I stand by the statement. You have assumed that the concrete remains
uncracked. If that is the case then one could rightly argue (as you have)
that the concrete helps make the pole stiffer. Once the concrete cracks
then the pole is at least theoretically no stiffer than an unfilled pole.
In reality this will depend on where the cracks in the concrete are
located.
However, I should like to remind you that the first rule of concrete is,
"Concrete always cracks."
As someone else pointed out: the concrete adds mass and this will change
the natural period of vibration of the pole and may even give the apparent
feeling that the pole is stiffer.
Now you tell me which is easier to install: a 3-inch pipe with a 3/16"
wall that has to be filled with concrete into the 3" opening, or a 3-inch
pile with a 5/16" wall that doesn't have to be filled with concrete. I
know which I would choose.
Glenn
Glenn
walls are thicker it will be stiffer, go all the way and say it is
solid 3" rod. The question was, would a pipe filled full of
concrete be stiffer and the answer is, yes of course. For a pipe
to bend it has to deform slightly. If it is full of concrete,
even cracked all over the place, it will resist deforming more.
All the Wal-Mart stores have pipes in front of the doors to stop a
car. They are filled with concrete to make them stiffer.
"Bob Morrison" <SpamF...@junk.com> wrote in message
news:MPG.209c0065d...@news.west.earthlink.net...
PeterD
wrote:
>In a previous post PeterD wrote...
>> >> I think the concrete stiffens the pole to better dampen out the
>> >> vibrations that can occur when the ball hits the rim. Also, alot of the
>> >> basketball pipes are multiple sections, so the concrete helps it act
>> >> like one structure instead of 3 pieces of pipe. I think the concrete is
>> >> a good idea for a satellite mount, as the wind can cause similar
>> >> vibrations and bending. I think you did good.
>> >
>> >I suspect it is more an issue of adding mass to the pole to change its
>> >resonant frequency than it is of adding stiffness.
>> >
>> >Matt
>>
>> IMHO, the response that alluded to the pole's mode of failure
>> (collapse) being blocked by the cement is more the factor, but I'm
>> sure resonence is a factor too.
>>
>
>Pouring concrete into a small diameter post seems a waste of effort to me.
>It's a heck of a lot easier to just get a bigger pole.
<g> Ah, but there's the rub: the antenna is designed for a certain
sized pole (usually 4") so you are not going ot get something bigger
in there without a lot of work.
Matt Whiting
> On Apr 27, 11:19 am, Bob Morrison <SpamFigh...@junk.com> wrote:
>> Pouring concrete into a small diameter post seems a waste of effort to me.
>> It's a heck of a lot easier to just get a bigger pole.
>
> Why don't you just admit you weren't thinking when you wrote your
> post, and move on. Lots of times I write stupid stuff too. Well, I'm
> afraid I don't write things *that* stupid, but you get the idea. If
> you try to defend a untenable position, it just gets worse.
>
> It's really hard for me to understand how you could have said, "I
> doubt that filling the pipe with concrete will have much affect on the
> overall stiffness of the pole."
>
> _Are you still standing by that statement?_
>
> A pipe filled with concrete, a 3" pipe for this example, is much
> stronger (and stiffer, if that's the term we want to use). Think about
Stiffness and strength are two completely different concepts. Come back
when you understand the difference.
Matt (not an SE yet, but really close now)
Matt Whiting
> The argument as you present it is kind of silly. Of course if the walls
> are thicker it will be stiffer, go all the way and say it is solid 3"
> rod. The question was, would a pipe filled full of concrete be stiffer
> and the answer is, yes of course. For a pipe to bend it has to deform
> slightly. If it is full of concrete, even cracked all over the place,
> it will resist deforming more. All the Wal-Mart stores have pipes in
> front of the doors to stop a car. They are filled with concrete to make
> them stiffer.
You also are confusing stiffness with strength. Buckling of the pipe is
more of an issue with strength than with stiffness. Stiffness is
relevant at all deflections from small to large, whereas, strength isn't
much of an issue until the load and thus deflection is rather large.
Bob is correct in saying that filling the pipe with concrete will have
very little affect on its stiffness. I will increase the strength if
the pipe is slender enough that buckling is the main failure mode.
Matt
Matt Whiting
The rebar on the pipe centerline was just wasted metal.
Matt
Nehmo Sergheyev
concepts, particularly with the issue at hand. Now, what I said was
this:
"A pipe filled with concrete, a 3" pipe for this example, is much
stronger (and stiffer, if that's the term we want to use)."
*I* specifically differentiated between the two terms, and I
parenthetically offered the term "stiffer" because that's the one he
used. I used "stronger" because that's easier to understand and I
believe that's what he meant anyway. But either term doesn't work. A
concrete-filled steel pipe is stronger and stiffer than one that is
empty.
It's absurd to argue otherwise.
I'm beginning to conclude you two have never been out in the field.
I've got a pipe filled with concrete two blocks from here. It's
stronger AND stiffer than the same pipe would be if it were empty.
Let's say it is used as a beam supported at both ends. A given amount
of weight in the center will make it deflect less than that same
weight on an empty pipe. Do you think otherwise?
The difference is so much, if I didn't know you both were humorless, I
would think you were joking.
++++++++++++++
http://www.takenaka.co.jp/takenaka_e/quake_e/cft/cft.htm
"Concrete-Filled Steel Tube (CFT) Structural System is a completely
new system based on filling steel tubes with high-strength concrete.
The CFT Structural System promises excellent structural
characteristics; including rigidity, strength, deformation capacity,"
http://tdworld.com/mag/power_concretefilled_steel_pole/
Concrete-Filled Steel Pole Goes Up in Southern Florida
http://www.ctsee.org.tw/%E5%87%BA%E7%89%88%E5%93%81/200310/ee0401-05.pdf
One of the main advantages is the interaction between the steel tube
and concrete: local buckling of the steel tube is delayed by the
restraint of the concrete, and the strength of concrete is increased
by the confining effect of the steel tube.
There's more in this search: http://snipurl.com/1iiu5 ,
--
(||) Nehmo (||)
----------------------------------------
Tom Cular
Snip:
The concrete fill of a thin wall tube, i.e.: a pipe pile or lally column
increases resistance to buckling in compression and bending failure in the
case of piles exposed to lateral loads, other than that, it just adds mass.
Tom
Matt Whiting
> They are not "completely different concepts"; they are related
> concepts, particularly with the issue at hand. Now, what I said was
> this:
No, they are completely different. Stiffness is related to the slope of
the stress/strain relationship (elastic modulus) in its linear range.
Strength is how high the curve goes before failure. Not the same at
all. A material can be very stiff (glass), yet not strong (glass with a
small surface crack). A material can be very strong (spring steel), yet
not very stiff (spring steel).
> "A pipe filled with concrete, a 3" pipe for this example, is much
> stronger (and stiffer, if that's the term we want to use)."
>
> *I* specifically differentiated between the two terms, and I
> parenthetically offered the term "stiffer" because that's the one he
> used. I used "stronger" because that's easier to understand and I
> believe that's what he meant anyway. But either term doesn't work. A
> concrete-filled steel pipe is stronger and stiffer than one that is
> empty.
>
> It's absurd to argue otherwise.
>
> I'm beginning to conclude you two have never been out in the field.
> I've got a pipe filled with concrete two blocks from here. It's
> stronger AND stiffer than the same pipe would be if it were empty.
>
> Let's say it is used as a beam supported at both ends. A given amount
> of weight in the center will make it deflect less than that same
> weight on an empty pipe. Do you think otherwise?
Let's say you support the empty pipe as you say above (as a simply
supported beam) and measure its deflection in the center. Now stand the
pipe up, fill it with concrete and let it cure and then support it the
same way again and measure the deflection in the center. Which case do
you think will have greater deflection? And now explain why your
stiffer pipe has more deflection than the less stiff pipe that has no
concrete.
Matt
Matt Whiting
And it really only helps in bending failure when buckling is the failure
mode.
Matt
Mike Hammer
I WAS having problems with the pole regarding buckling and bending failure until
I gave it some Viagra. Now it is stiff, straight, and hard.
Hey! Who painted the smiley face on the backboard? (-;
Glenn
"Matt Whiting" <whi...@epix.net> wrote in message
news:cbyYh.9478$Oc.2...@news1.epix.net...
>
> Matt (not an SE yet, but really close now)
Ahhh, that explains a lot. Book learnt but no experience. For
your information, a hole in the ground is where you can pour a
foundation, your butt is just above your legs. You will have to
know the difference when you get out into the real world.
Nehmo Sergheyev
> Let's say you support the empty pipe as you say above (as a simply
> supported beam) and measure its deflection in the center. Now stand the
> pipe up, fill it with concrete and let it cure and then support it the
> same way again and measure the deflection in the center. Which case do
> you think will have greater deflection? And now explain why your
> stiffer pipe has more deflection than the less stiff pipe that has no
> concrete.
I'll go along with that experiment. But you can't make the
conclusions, let alone explain them, before you conduct the
experiment.
The pipe is a beam, 8 feet from support to support. The exterior
diameter is 3 inches. The wall thickness is the same in both. We'll
use schedule 40 because that's the example I think I can get.
One pipe is empty and is referred to as "empty"; the other pipe is
filled with cured concrete and is called "filled".
The deflection in either case is hard to measure when we are only
using the weight of the pipe itself to cause the deflection. However,
I can stand on the center of the pipe. I weigh 211 pounds. (If the
experiment is conducted without me, someone else can substitute.)
In the filled pipe, there will be small deflection. It would even be
hard to measure with regular rulers.
In the empty pipe, there will be considerable, easily noticeable and
measurable deflection.
There will be more deflection in the empty pipe than in the filled
pipe.
You disagree with my last 3 paragraphs. Correct? Now, all we have to
do is find an acceptable way to do this experiment. We need someone
impartial to judge, and perhaps you want to put some money on this?
Well, I don't want to be rude. If you don't want to bet, that's okay.
But the loser should have to do something.
Michael Bulatovich
"Glenn" <pil...@kc.rr.com> wrote in message
news:4633a0e8$0$15181$4c36...@roadrunner.com...
That was rude, and unnecessary.<PLONK>
Nehmo Sergheyev
> That was rude, and unnecessary.<PLONK>
It's not something I would have wrote, but it's not that horrible. If
that's the level you plonk at, you're going to be doing a lot of
plonking. Glenn didn't name call, threaten, or even
swear. Indeed, he was trying to avoid directly saying Matt doesn't
know his ass from a hole in the ground.
And if you'll notice, Matt, in different ways, is rude a lot himself.
For example, he's paraphrasing me incorrectly in this very thread.
He's pretending there's some third party reading his post by itself. I
suppose If they were to do that, they might be inclined to side with
him. It's vary irritating, and he knows it. When you respond to Matt,
the first thing you have to do, time and time again, is attempt to
correct what he claims you said.
Now, that's enough of that. The issue is simply whether a concrete-
filled steel pipe is stiffer than one that is empty. I say it is. Matt
and Bob, amazingly, disagree with me.
Glenn was trying to explain how Matt could possibly be thinking this
way. I've been wondering myself. Anybody who's had any real-world
experience with a concrete-filled tube knows it's stiff. Thus, Matt
must not have any experience of this nature.
Matt Whiting
> On Apr 28, 8:05 am, Matt Whiting <whit...@epix.net> wrote:
>> Let's say you support the empty pipe as you say above (as a simply
>> supported beam) and measure its deflection in the center. Now stand the
>> pipe up, fill it with concrete and let it cure and then support it the
>> same way again and measure the deflection in the center. Which case do
>> you think will have greater deflection? And now explain why your
>> stiffer pipe has more deflection than the less stiff pipe that has no
>> concrete.
>
> I'll go along with that experiment. But you can't make the
> conclusions, let alone explain them, before you conduct the
> experiment.
>
> The pipe is a beam, 8 feet from support to support. The exterior
> diameter is 3 inches. The wall thickness is the same in both. We'll
> use schedule 40 because that's the example I think I can get.
>
> One pipe is empty and is referred to as "empty"; the other pipe is
> filled with cured concrete and is called "filled".
>
> The deflection in either case is hard to measure when we are only
> using the weight of the pipe itself to cause the deflection. However,
> I can stand on the center of the pipe. I weigh 211 pounds. (If the
> experiment is conducted without me, someone else can substitute.)
The scenario is the self-weight only, no applied load.
Matt
Matt Whiting
From the mouths of babes...
Matt Whiting
Michael, don't sweat it. People of his IQ say dumb things all the time.
Matt
Michael Bulatovich
"Nehmo Sergheyev" <neh...@hotmail.com> wrote in message
news:1177792733....@l77g2000hsb.googlegroups.com...
> On Apr 28, 2:46 pm, "Michael Bulatovich" <Ple...@dont.try> wrote:
>> That was rude, and unnecessary.<PLONK>
>
> It's not something I would have wrote, but it's not that horrible. If
> that's the level you plonk at, you're going to be doing a lot of
> plonking. Glenn didn't name call, threaten, or even
> swear.
I can and I do, as you say. Newsgroups are like the first hockey tryout with
50 skaters on the ice. You don't (can't) pick out the good ones, it takes
too much time. The cuts are quicker and easier to see and make. When the
crowd is gone you can focus on qualities of individuals.
--
MichaelB
www.michaelbulatovich.ca
Matt Whiting
> On Apr 28, 2:46 pm, "Michael Bulatovich" <Ple...@dont.try> wrote:
>> That was rude, and unnecessary.<PLONK>
>
> It's not something I would have wrote, but it's not that horrible. If
> that's the level you plonk at, you're going to be doing a lot of
> plonking. Glenn didn't name call, threaten, or even
> swear. Indeed, he was trying to avoid directly saying Matt doesn't
> know his ass from a hole in the ground.
>
> And if you'll notice, Matt, in different ways, is rude a lot himself.
> For example, he's paraphrasing me incorrectly in this very thread.
> He's pretending there's some third party reading his post by itself. I
> suppose If they were to do that, they might be inclined to side with
> him. It's vary irritating, and he knows it. When you respond to Matt,
> the first thing you have to do, time and time again, is attempt to
> correct what he claims you said.
Show one place where I paraphrased you incorrectly. Just one example.
> Now, that's enough of that. The issue is simply whether a concrete-
> filled steel pipe is stiffer than one that is empty. I say it is. Matt
> and Bob, amazingly, disagree with me.
Let me see ... Bob is a PE and SE with many years of experience. I'm a
PE and nearly complete with a graduate degree in SE (need to complete
the final capstone project). And your credentials are???
> Glenn was trying to explain how Matt could possibly be thinking this
> way. I've been wondering myself. Anybody who's had any real-world
> experience with a concrete-filled tube knows it's stiff. Thus, Matt
> must not have any experience of this nature.
Amazing that you can make this claim when you don't even know the
difference between strength and stiffness.
Matt
Michael Bulatovich
Plonking requires no sweat, and this is not a question about IQ. It's about
EQ.
--
MichaelB
www.michaelbulatovich.ca
Matt Whiting
:-), yes, very true!
Nehmo Sergheyev
> The scenario is the self-weight only, no applied load.
Why would you be afraid of a little weight? Weight is the force that
is going to make the pipe deflect. Besides, as I said, the deflection
of filled pipe is going to be hard to measure if we only use the
weight of the beam. We have to measure relative stiffness, you know.
Nehmo Sergheyev
> Glenn wrote:
>
> > "Matt Whiting" <whit...@epix.net> wrote in message
The phrase, "pearls of wisdom can come from the mouths of babes,
fools, and drunks", which is often used elliptically as you did, means
that something said my someone uncorrupted or uninhibited is true.
Thus, in the context you used it, you are saying what Glenn said is
true. In other words, you are agreeing you don't know your ass from a
hole in the ground.
Bill
I filled my 10 ft. high 3 inch schedule 80 pipe with concrete (3 ft. is
underground, total pipe length 13 ft.).
Scientific results:
Before filled with concrete: I would tap on the top of the pipe with my
hand and the pipe would "wiggle". And it would continue to "wiggle" back and
forth for 10 seconds or more.
After filled with concrete: I tap on the top of the pipe with my hand and
the pipe "moves" just a little and stops moving after about a second.
So this is very good for my motorized 12 ft. wire mesh satellite dish
antenna. These things point at satellites 25,000 miles up in the sky.
Needless to say, they need to be aimed extremely accurately. 1/8 inch in
aiming can make the difference in being able to lock in a satellite or not
(with some of the weaker satellites). And prior to concrete filling, I would
guess the pipe was wiggling 1/2 inch to 3/4 inch back and forth.
So having the wind blow on the dish and making it "wiggle" constantly would
not be a good thing.
As to the size of the pipe, my dish has a mounting collar for this size
pipe.
I left a 10 ft. length of 1/2" rebar in the concrete in the pole. I
basically used this along with hammering the side of the pole to get the
concrete to "settle" while pouring. I would slide the rebar up and down
inside the pole. And hammer on the sides of the pole with a hammer.
Then I just left the rebar inside the pole when I was done with this. I
don't think there is any need for the rebar in the concrete??? But I would
have had no other use for it, so might as well leave it in the pole...
Anyway "wiggle" problem solved.
And I love the internet! Ask a question and get all sorts of technical
discussion. Another interesting thing for you engineering types would be a
"tuned mass damper" for my satellite pole! Info on tuned mass dampers...
http://en.wikipedia.org/wiki/Tuned_mass_damper
Mike Hammer
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.
Bob Morrison
> Before filled with concrete: I would tap on the top of the pipe with my
> hand and the pipe would "wiggle". And it would continue to "wiggle" back and
> forth for 10 seconds or more.
>
> After filled with concrete: I tap on the top of the pipe with my hand and
> the pipe "moves" just a little and stops moving after about a second.
>
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
Structural & Civil Engineering
Poulsbo WA
bob at rlmorrisonengr dot com
JTMcC
"Bob Morrison" <SpamF...@junk.com> wrote in message
news:MPG.20a0e69ec...@news.west.earthlink.net...
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.
Bob Morrison
> 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.
>
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.
Mike Hammer
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.
Matt Whiting
Yes, as I mentioned some time back, adding that much mass will make a
lot of different in the vibration characteristics.
Matt
Matt Whiting
> In a previous post JTMcC wrote...
>> 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.
>>
>
> 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.
Yes, and the latter has the advantage of dramatically increasing
stiffness and strength as well as changing the natural frequency.
Matt
JTMcC
> The whole subject has gotten out of hand. > Bob Morrison, PE, SE
> R L Morrison Engineering Co
> Structural & Civil Engineering
> Poulsbo WA
> bob at rlmorrisonengr dot com
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.
Matt Whiting
If you have done the research, post one source here that shows the
stiffness gain from filling a tall, skinny pipe with concrete.
Matt
Bob Morrison
> If you have done the research, post one source here that shows the
> stiffness gain from filling a tall, skinny pipe with concrete.
>
MY SENTIMENTS EXACTLY!
(and yes I meant to shout!)
--
Bob Morrison
> 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.
>
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.
--
JTMcC
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
Mike Hammer
says...
>
>In a previous post JTMcC wrote...
>> 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.
>>
>
>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.
You're talking economics here.
>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.
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.
>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.
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.
Bob Morrison
> 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.
>
> >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.
>
> 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.
>
>
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.
Mike Hammer
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.
Bob Morrison
> 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.
>
Exactly! That's all I've been trying to say.
Glenn
Isn't it time we shook hands and moved on? [g]
"Bob Morrison" <SpamF...@junk.com> wrote in message
news:MPG.20a24f98f...@news.west.earthlink.net...
Bob Morrison
> You were?? Could have fooled me.
>
> Isn't it time we shook hands and moved on? [g]
>
Okay by me.
I promise not to post any more on this subject.
JTMcC
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.
> Bob Morrison, PE, SE
> R L Morrison Engineering Co
> Structural & Civil Engineering
> Poulsbo WA
> bob at rlmorrisonengr dot com
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.
Matt Whiting
I wouldn't recommend a trip to Vegas as your bluffing technique needs
some work.
Matt
Matt Whiting
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
Matt Barrow
> You were?? Could have fooled me.
>
Cartoons fool you.
JTMcC
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.
Matt Whiting
Having one's bluff called is so embarrassing. When you can't provide
the data you have to resort to insults. How sad...
JTMcC
"JTMcC" <firstra...@citlink.net> wrote in message
news:PH9_h.7855$ya1....@news02.roc.ny...
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 ; )
>
>
JTMcC
>
> Having one's bluff called is so embarrassing. When you can't provide the
> data you have to resort to insults. How sad...
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.
Bob Morrison
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.
> I am working on a project where I am filling a schedule 40 8” a53
> galvanized pipe with concrete. The pipe is a primary support to a
> solar array. I was wondering if you know what the best way to fill this?
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.
--
RicodJour
> I have a 10 ft. high 3 inch diameter pole which I filled with concrete
> (sand/topping mix). It took one and a half bags to fill the pipe.
>
> I am doing this for a satellite dish antenna so the pole will be more stable
> and not "wiggle".
>
> Basketball mounting poles also have this done I am told....
>
> Question: All that concrete is basically enclosed in the pipe and there is
> just the opening at the top. How would the concrete cure? How long would it
> take to cure? (Just curious...)
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
Kevin Hobart
Air can be depressed. cement can't. I'm sure we can agree air in metal makes
metal weaker. A pipe filled with cement would be almost impossible to bend.
Vs. the same pipe with only air inside it. So, in answer to the question, I
would say that I would go one step further and fill a few sticks of conduit
with cement and add them to the pipe, then fill the pipe with cement. Just
depends how stiff you want to make it. The "Anchor Cement" sets up in about 10
minutes. I want to believe it cures at just over 7,000 psi in just a day or
so. If you wanted to add a little conduit to it , I bet you could double the
strength as well. I hope this helped.
--
for full context, visit https://www.homeownershub.com/construction/fill-tall-pole-with-concrete-cure-8193-.htm
Scott Hall
You are an idiot, if you fill the pole with sand or gravel it will be
immensely stronger than if left hollow. The idea that the concrete cracks has
any impact on the strength of the overall strength is preposterous.
Robert vertin
What the hell? You are an engineer?? Even if concrete cracks, any deformation
is limited to the volume such crack will allow deformation into ... you could
fill the pipe with sand and cap it off and enjoy some benefits of this same
principle. Have you ever wondered why they fill safety poles with cement ? Duh
BigRed52
--
For full context, visit https://www.homeownershub.com/construction/fill-tall-pole-with-concrete-cure-8193-.htm