Reinforced concrete stress/strain - with Moment and Axial Load - Service loads 1

[mte12]

I've been looking for a method to estimate stress and strain in reinforced concrete, when subject to moment and axial load, particularly bars in tension. This is at service loads which may not necessarily be at ultimate state.

Is there a prescriptive method available to follow?

 

[HTURKAK]

If you are looking for elastic stresses , you may use working stress design method and look to the old Reinforced Concrete books . If this is a specific case , you may post the details to get better responds.

 

[mte12]

Thanks HTURKAK, the methods in textbooks as far as I can see deal with ultimate case or 4 conditions for column (pure axial, pure bending, balanced and neutral axis at edge).

For other cases, not sure about input for neutral axis location and strains in concrete and steel.

 

[IDS]

This is also covered by new reinforced concrete design books. Standard deflection and crack width calculations are based on elastic response in the steel and concrete in compression.
The basis of the calculation is to find the neutral axis depth for which the eccentricity of the reaction forces is equal to the eccentricity of the applied loads, then scale the maximum concrete stress so that the total reaction bending moment is equal to the applied moment. This is usually done with an iterative procedure, but I prefer to use a closed form solution, which you can read more about at: https://newtonexcelbach.com/2008/11/05/reinforced-concrete-section-analysis-7-rectangular-sections/

 

[mte12]

Ok thanks Doug I'll look into it, looks very complicated

 

[mte12]

Doug, your spreadsheet is very detailed and uses visual basic, having a bit of a hard time understanding it.
I was wondering if there's any literature which explains the method to someone not familiar with concrete.

I didn't get to checking, but is it correct that the force in concrete is based on a curve (similar to a parabola), rather than a block. And how do you calculate for the area under curve?
And guess you use an iterative procedure?