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HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

(OP)
Hi, guys.
Any of you know how to determinate the MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

Prior to concrete cracking and assuming composite behavior, it would be reasonable to take an average weighted based on the area of each material.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

(OP)
ok, but for example:
Using a steel tube with:
- 140 mm of external diameter and 130 mm of internal diameter;
- E = 200 e9 Pascal;
- DENS = 7850 kg/m³
Filled with concrete with:
- E = 26.3 e9 Pascal;
- DENS = 2400 Kg/m³
what the Equivalent Modulus of Elasticity??

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

Same answer. Why not give it a try and post your work. We'll set you straight if thing go awry.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

I presume that's in axial compression? If so, you can ignore the concrete cracking.
Equate the deflection of the pipe and the concrete and solve for an equivalent composite section elastic modulus.

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

50.3E3 MPa

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

(OP)
I`ll proceed with a modal analysis.
So, presuming that the concrete wont crack. How can i determinate the equivalent elasticity modulus for a equivalent composit section?

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

(OP)
How you calcutate that to get 50,3 e3 MPA, Trenno???

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

Find area of steel (As).

Find area of concrete (Ac).

Sum the two areas (At).

Take weighted average of E.

(As/At)*Es + (Ac/At)*Ec = 50.3E3 MPa.

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

(OP)
Ok, Trenno.
But where you got that formula??
And how can i calculate the equivalent poisson ratio??

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

It's not a formula, it's just the method described by KootK. Maybe google 'weighted average.'

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?


Quote:

I`ll proceed with a modal analysis.

So are you interested just in stiffness under axial load, or also bending?

If you need bending stiffness as well, it gets more complicated. See for instance:

http://ccvi.ce.gatech.edu/Papers%20March%20PDF/Whe...

But for a lower bound estimate you could ignore the concrete.

Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

What does the Eurocode say?

Never looked myself but I know of atleast one steel high rise in Brisbane that the steel filled tubes were designed to the Eurocodes.

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

(OP)
I`ll look. Thx :D

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

Quote (OP)

And how can i calculate the equivalent poisson ratio??

With some difficulty I imagine. As an approximation, you could workout the steel hoop strain associated with restraining the dilation of the concrete. While inexact, this should give a reasonable characterization of the composite poisson ratio.

What is the nature of the thing that you're designing? Are you simply seeking appropriate values for use in modelling software?

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

(OP)
I looked on Eurocodes, but i did not found anything of how to determinante poisson`s ratio.
Anyone have a ideia?

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

(OP)
Hi, KootK.
I am modeling a transmission tower using steel tubes filled with concrete on the amounts and corner frames for every other element of the tower.
I am modeling that on ANSYS. My code for that its on attachment.
My questions is:
1) It`s correct the affirmation from Trenno to get the equialent modulus of elasticity?
2) How can i get the equivalent density of the element?
3) How can i get the equivalent poison`s ratio?
4) Can i use the element beam188 - SECDATA - CSOLID, using the equivalent properties?
5) The model using the answer of the question 4 will give me the right frequencies of my problem?
The code on attachment its from a tower using corner frames and tubes on amounts (GROUP = MONT).

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

Quote (OP)

1) It`s correct the affirmation from Trenno to get the equialent modulus of elasticity?

Probably. You should run the weighted average calc for your self to verify Trenno's work.

Quote (OP)

2) How can i get the equivalent density of the element?

Again, use a weighted average.

Quote (OP)

3) How can i get the equivalent poison`s ratio?

See my previous post for a possible estimation procedure.

Quote (OP)

4) Can i use the element beam188 - SECDATA - CSOLID, using the equivalent properties?

I'm afraid that I'm not familiar with these elements.

Quote (OP)

5) The model using the answer of the question 4 will give me the right frequencies of my problem?

I'm afraid that I'm not familiar with these elements.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

(OP)
what element you are falimiar to simulate a steel tube filled with concrete? Or questioning with other words: what element you recommend to use on my situation?
I`ll calculate my self, scam and post it here to you see. ok?

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

Quote (OP)

what element you are falimiar to simulate a steel tube filled with concrete? Or questioning with other words: what element you recommend to use on my situation?

I've never tried to do this in software so I'm afraid that I'm unable to be of much help regarding your ansys element choices.

Quote (OP)

I`ll calculate my self, scam and post it here to you see. ok?

Sure.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

Better watch out for that scam, KootK!

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

I'll keep my antennae up in case he wants me to temporarily hold onto his inheritance en route from King Filipe of Spain. Most of my retirement savings are already tied up with a Nigerian prince anyhow.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

If you have time, take a sample and fill with concrete and test it at a lab.

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

1. Looks good.

2. Looks good.

3. Probably incorrect. I don't feel that weighted average is appropriate here. See my recommendation above.

4. I can't say. Hopefully someone else here with better FEM chops can comment.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

(OP)
I tried simulations with different Poison`s ratio to find frequencies, and my results are:
v freq (Hz)
0,21 1,146
0,22 1,145
0,23 1,145
0,24 1,144
0,25 1,144
0,26 1,144
0,27 1,143
0,28 1,143
0,29 1,142


what you think about this results? Its better use a Poison`s ratio between 0,24 to 0,26?

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

Taking a step back here...

You've varied your poison's ratio by around 27.6% difference.

Now within that range, your frequencies have only varied by around 0.35% difference.

What does that tell you?

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

Are all the calculations based on there being any kind of bond between the steel pipe and the concrete fill?

The smooth face of the inside of the pipe and the inherent shrinkage of the concrete during curing seems to indicate there there is not any real bond (if any). The wetter the concrete for pumping coupled with the normal shrinkage of all concrete seems to present a problem with any kind of bond for composite construction.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

RE: HOW TO DETERMINATE THE MODULUS OF ELASTICITY OF A STEEL TUBE FILLED WITH CONCRETE?

Usually shrinkage of the concrete isn't an issue in this type of construction because there is limited water loss due to the steel tube preventing shrinkage so its cured very well.

No code I've ever seen uses a weighted average like has been discussed here. Usually some sort of sum of the concrete and steel modulus and second moment of inertia is calculated i.e. sum of E x I, this is sometimes modified to bring the stiffness in line with real world tests. I believe the stiffness of the composite member is pretty well understood in terms of research, so this approach is outlined in a number of international codes relating to the design of composite concrete filled sections.

Refer to the attached (page 16) for an example of how a code approaches this, this document is based on the previous revision of Eurocode 4. But the same principles apply in the latest version with some minor changes.

The Australian Bridge code AS5100.5 also has a similar derivation which I am more familiar with, this standard is based on Eurocode 4 with some small changes to make it more New Zealand/Australian-ised.

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