Learning Forum

[Osamashakil]

Hello,

I m checking stress-strain curve of the default NL concrete model (Drucker Prager with tensile pressure failure criteria), and got following stress-strain curve for concrete (picture attached). I m using default parameters of the concrete model and got the curve using 50 mm cube. I want to know that why the stress-strain curve is not according to reality?

The conventional stress-strain curve found in the literature is much different than obtained from this model.

 

anyone, please guide me for possible reasons.

 

 

 

[peteroznewman]

Please provide data from a stress-strain curve from the literature.

Also upload an archive of the model you used to create the stress-strain curve of the NL concrete material.

[Osamashakil]

Thank you so much for your response.

Ansys files have been attached.

Failure of concrete must occur at strain level of 0.003.

The curve must look like this.

[Osamashakil]

 

[peteroznewman]

Thanks for the stress-strain curve for concrete.The figure in black is more of an annotated illustration and shows strains of 0.3%, while the figure higher up with the curve in blue looks like a plot of data but that shows strain up to 4.5%. Where did that data come from?

I have some experience with converting an Engineering stress-strain curve for a ductile material into a True Stress - True Strain curve that can be used in a Multilinear plasticity model.

How have papers in the literature used the data you show to create a material model?  Are they using plasticity?

[Osamashakil]

Actually, I have taken a cube in Ansys. Bottom face of cube is fixed and on top face, I m applying displacement is compression. When I plot stress-strain curve (shown in blue graph) from Ansys, the behavior of stress-strain curve is totally different from conventional strains keeps on increasing, I have shown limited data in graph. I have searched about it and find out that maybe drucker-pragar concrete model is very highly plastic. 

The black curve from literature they are using simple concrete without plasticity.

so itss mean that NL concrete is Ansys is highly plastic? moreover screenshot I have shared above from Ansys it shows pressure vs yield stress criteria, it doesnot ask for compressive strenght for concrete. so which compressive strength of concrete Ansys actually using?

[Osamashakil]

In short I m just checking how this Drucker-Prager concrete works. How it is different than conventional one? is it highly plastic? n how pressure vs yield stress data in definition works? n what if I have to change the compressive strength of concrete?

[sayed]

sir i need to perform splitting tensile strength of concrete and find stress strain curve and failure pattern. can you help me in giving the properties of concrete and steps to solve.