I'll go along with that experiment. But you can't make the
conclusions, let alone explain them, before you conduct the
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
There will be more deflection in the empty pipe than in the filled
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.
(||) Nehmo (||)
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 (||)
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.
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.
(||) Nehmo (||)
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.
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.
(||) Nehmo (||)
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.
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.
The results are in!
I filled my 10 ft. high 3 inch schedule 80 pipe with concrete (3 ft. is
underground, total pipe length 13 ft.).
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
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...
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