why I am getting stresses higher than the ultimate strength of concrete in ABAQUS?

[compe_ad]

I am modeling a concrete cylinder compression test. Loading is applied along z direction, and I am checking the sigma_33 stresses. I am having maximum signma_33 at the element centroid around 78 MPa (see attached graph). I don't get it why it is higher than the ultimate concrete strength of concrete (58 MPa).
Which stress does ABAQUS consider to check yielding and damage for concrete material?

 

[bkal]

It is difficult to say why as you have provided little information, but one of the reasons might be that the confined concrete strength (i.e. multiaxial compression) is higher than its uniaxial strength. Depending on your boundary conditions, load application etc., you might have triaxial compression where you have high sigma_33.

 

[compe_ad]

It is an uniaxial loading. Bottom of the cylinder is fixed, and a pressure load is applied at the top (see attached). I agree what you are saying but clearly its a uniaxial loading case. This is what creating a confusion.

 

[SWComposites]

Is the bottom fixed in all dof’s? Or only in axial dof? If fixed in all dof you have over constrained the bottom resulting in 3d stress state.

 

[compe_ad]

THanks! It is fixed in all dof. Can you please explain your point a bit more?

 

[SWComposites]

Huh?? Basic material elastic response.
When you apply a stress in one direction, a material will deform in the directions transverse to the applied stress.
You have restrained these transverse displacements.