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

[MAPB1994]

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

 

[KootK]

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.

 

[MAPB1994]

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??

 

[KootK]

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.

 

[BUGGAR]

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.

 

[Trenno]

50.3E3 MPa

 

[MAPB1994]

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?

 

[MAPB1994]

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

 

[Trenno]

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.

 

[MAPB1994]

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

 

[Trenno]

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

 

[IDS]

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 March PDF/Wheeler.pdf

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

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[Trenno]

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.

 

[MAPB1994]

I`ll look. Thx

 

[KootK]

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.

 

[MAPB1994]

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

 

[MAPB1994]

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).

 

[KootK]

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.

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

Again, use a weighted average.

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

See my previous post for a possible estimation procedure.

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

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

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.

 

[MAPB1994]

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?

 

[KootK]

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.

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.