Drawback with concrete stress-strain diagram

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Hi!
As I mentioned before, I was working in a model with distribuited plasticity using fibers. In the input data, I defined the
following behaviour for the concrete cover:

concreto 1.PNG (31.56 KiB) Viewed 2316 times

Moreover, while I was analyzing my results in the concrete stress-strain diagrams and saw the following:

fibras de concreto 1.PNG (7.4 KiB) Viewed 2316 times

It looked like that everything was good, but the last stretch was constant after of surpassing the maximum strain (-0.0038 when it should finish) until -0.0066 aproximately. I looked it weird beacuse I did not include the constant stretch and supposetely the concrete breaks in that strain (-0.0038) as you can see in the first picture.
I could think that probably was the target strain due to the target displacement in the model, because if I increase it more than the maximum strain, the rest stretch is constant as the second picture. Hence, my question is more about why the program show me that stretch or what behaviour the program identifies there. I would really appreciate if you can help me.
Thanks in advance

[STKO Team]

Dear user,

It is perfectly normal: the Concrete01, defines the point (epsCU, fpCU) as the last point after which you have a constant plateau:

c01.png (78.19 KiB) Viewed 2298 times

If you want to make it drop after an ultimate strain, you need to use the MinMax material in combination with the Concrete01:

c01_minmax.png (71.86 KiB) Viewed 2298 times