# Steel reinforced concrete elastic modulus help

1. Jan 20, 2010

### taylaron

I'm inputing data into a SolidWorks material profile, but i'm having difficulty determining the value of the elastic modulus (psi) of steel reinforced concrete

i'm looking at the following source for material properties:

http://www.fhwa.dot.gov/pavement/pccp/pubs/05081/chapt3.cfm [for elastic modulus of concrete and steel rebar]
Here it gives young's modulus of concrete and the value for the rebar.

"Young's modulus of concrete at 28 d, Ec,28 (GPa (x 106 lbf/in2)) 33.10 (4.80)1 and 34.48 (5.0)2

Young's modulus of steel rebar (GPa (x 106 lbf/in2)) 200.00 (29.00)"

I'm confused because steel reinforced concrete combines both steel and concrete, which value or at what proportions do I use? Of course the whole point of adding steel is to make the concrete less elastic, so obviously I cant use concrete, but I obviously cant use just steel either. See my dilemma?

Also I don't understand how to obtain psi from "(GPa (x 106 lbf/in2)) 33.10 (4.80)1 and 34.48 (5.0)2" either.

Thanks for your help,

-Tay

2. Jan 31, 2010

### taylaron

Thoughts anybody?

3. Mar 21, 2010

One way to calculate mechanical properties, such as young modulus, of reinforced materials is to use the "Rule of Mixtures":

"Rule of Mixtures is a method of approach to approximate estimation of composite material properties, based on an assumption that a composite property is the volume weighed average of the phases (matrix and dispersed phase) properties."

http://www.substech.com/dokuwiki/doku.php?id=estimations_of_composite_materials_properties

For longitudinal direction:

$$E_{\mbox{composite}} = E_{\mbox{mat1}}*V_{\mbox{mat1}} + E_{\mbox{mat2}}*V_{\mbox{mat2}}$$

where $$V_{\mbox{mat1}}$$ and $$V_{\mbox{mat2}}$$ are the volume fractions of the materials on the composite.

however im not sure if it can be used on reinforced concrete problems.

http://www.sciencedirect.com/scienc...serid=10&md5=849c74eae802eee3b22e8ff930c063be

4. Mar 21, 2010

### Studiot

Edit just noticed the date of the original post.

If you are going to do it that way you need the 'equivalent section' concept.

You transform either the steel or the concrete to an equivalent section of the other, using the ratio of elastic moduli as 15:1 and the fact that you want both to reach maximum allowable stress simultaneously.

The actual calculation proceedure depends upon the structural nature of the problem, and the materials.

What sort of reinforcement do you mean, rods or fibres?

Last edited: Mar 21, 2010