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?

 

[Trenno]

Better watch out for that scam, KootK!

 

[KootK]

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.

 

[MAPB1994]

Look this:

 

[oldestguy]

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

 

[KootK]

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.

 

[MAPB1994]

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?

 

[Trenno]

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?

 

[concretemasonry]

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.

 

[Agent666]

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.