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Hello! Sir/Madam is there any literature about constitutive model and failure criteria of (Damage TC3D) . Also looking for details of different parameters of Damage TC3D Material Model used in STKO.

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The description of each material parameter is given in the bottom text-box of the Property Editor, whenever you click on a material parameter.

Here is a reference for the DamageTC3D material. Though, at the time that article was written, that material model was not implemented in OpenSees, but in another FEM software. But it is pretty much the same.

https://www.researchgate.net/publicatio ... hear_walls

Hello STKO Team!

The part of the model related to damage is described quite clearly, however, there is no description of the plastic part of the model in this article. Could you please give us a link to the articles where the plastic part along with the description of the way how it is combined with damage are described?
I' ve read the following articles but I can not be sure that they describe the plastic part of TC3D model:

1. Faria, R., Oliver, J., & Cervera, M. (1998). A strain-based plastic viscous-damage model for massive concrete structures. International journal of solids and structures, 35(14), 1533-1558.
2. Faria, R., & Oliver, X. (1993). A Rate Dependent Plastic-Damage Constitutive Model for Large Scale Computations in Concrete Struktures: Monografia. Centro internacional de Métodos Numéricos en ingenieria.
3. Wu, J. Y., Li, J., & Faria, R. (2006). An energy release rate-based plastic-damage model for concrete. International journal of Solids and Structures, 43(3-4), 583-612.



Best Regards,
Aleksandr

Dear Aleksandr,

You are right, at the time I wrote the article, it was a pure damage model.
We still have to publish an article about the plastic part.

However, it is similar to how it is described here:
http://cervera.rmee.upc.edu/papers/1998 ... -based.pdf

In the sense that plasticity is introduced as an overall effect, without following the classical theory of incremental plasticity, as it would require an internal iterative process, while the aim of this material is to be fast and robust.

If you need some specific clarification, please let me know

Dear STKO Team,

thank you for your answer.
I need some time to deal with this new approach and then, I will prepare questions that will be unclear for me.
By the way, your solution with Bézier curves for descending part of the law in compression for damage model is really elegant in terms of math as it preserves function continuity!

Best Regards,
Aleksandr

You're welcome, and thank you!

Hello STKO Team!

Having read all the information you sent, I still have three questions on the model left:

1. Taking into account non-smooth transition between positive and negative failure surfaces, numerical problems may arise in case stress condition hits the region of the surface connection. How the numerical algorithm deals with this zone and how can stress-strain evolution can be described there?
2. In the article plasticity is adopted only for negative failure surface. Could you please descride how it is extended to tension and how it works in that zone?
3. How the failure surface evolve in case both plasticity and failure take plase?

Best Regards,
Aleksandr Dudchenko

1. Taking into account non-smooth transition between positive and negative failure surfaces, numerical problems may arise in case stress condition hits the region of the surface connection. How does the numerical algorithm deals with this zone and how can stress-strain evolution can be described there?

It can create problems in classical plasticity-based models, where you need the gradients of the yield/potential surfaces. DamageTC3D is a damage-based model (plasticity is included as a simplified function of damage, not using the concept of return mapping) so there is no problem for that.
The positive part of the stress acts on the positive surface alone, the same for the negative. The response is later re-composed.

2. In the article, plasticity is adopted only for negative failure surfaces. Could you please describe how it is extended to tension and how it works in that zone?

It is a bit hard to explain here because we still need to publish about this topic. Anyways you can think that we compute the plastic equivalent uniaxial strain as a portion of the total strain and damage (in both positive and negative parts). Then the direction of the plastic strain is a function of the tesile/compressive stress part

3. How the failure surface evolve in case both plasticity and failure take plase?

They evolve indipendently as explained in the paper, the plasticity do not influence this feature.

Dear STKO Team,

the first question is clear. As for the second one I'll be waiting for your article.
So, we have the same surfaces for corresponding plasticity laws (let's call them tension and compression yield surfaces) that evolve independently on damage ones. Am I correct?

Best Regards,
Aleksandr

Dear Aleksandr,

Yes you are correct!

Best regards

Lucy