How to calculate the parameter in Concrete Damage Plasticity

[adrianuk]

Hello, I want to ask that how to calculate the yield stress & Inelastic strain in compressive behavior, and also yield stress & cracking strain in tensile behavior in Concrete Damage Plasticity. Do they have different value for different grade of concrete?

 

[adrianuk]

If I have different value of ultimate concrete compressive strength: 30MPa, 40MPa, 50MPa

 

[adrianuk]

i tried to search for the answer and obtain the following result.
However, I don't know how to calculate Total tensile strain(epsilon c & epsilon t)

 

[pcsoin]

Hello,
I have the same problem, did you resolve it, if yes how do you obtain the tensile stain?
Thank you in advance.

 

[Martensite_Steel]

The total strains don't have to be calculated. Go ahead and make an excel sheet with the total strains in a column. That means, you could start with 0 and add 0.0001 in every row (although I would suggest to start with the maximum linear elastic strain (let's call it "eps_lim"), since the material behavior below this point is controlled by the elastic card of your material model, anyway).

So, eps_total could look like this:

eps_total,1=eps_lim
eps_total,2=eps_total,1+0.0001
eps_total,3=eps_total,2+0.0001
.
.
.
and so on.

The CDP model then expects the inelastic part of the strain as input. How it is calculated is written in the pictures from the manual, that you attached in your third post. You could take a look in the following paper. Although it is written in german, the relevant formulae and the comparison of different concrete models can be well understood: Link

Good luck

 

[AleksaBgd94]

Hello Adrianuk,

yes, they have different values for different grades of concrete.

Which code do you use?
I am just familiar with Eurocode 2, and the inelestic compressive behaviour is defined in Eurocude 2 with the following equation:

σc = fcm•(kη-η^2)/(1+(k-2)η) , η ≤ ε_cu1/ε_c

For the values of strain greater than ε_cu1 you can search for suggestions of some researchers.

I defined tensile behaviour as yield stress-displacement curve according to equation proposed by Hordijk (1992).

As Martensite Steel mentioned, the most important part is that the input parameters are inelastic strain or displacement and yield stresses. This means that you just enter the values of strain which correspond to the values of stress greater than 0.4fcm, if we talk about concrete sibjected to compression according to Eurocode 2 and the values of strain (displacement) which correspond to the values of stress greater than fctm if the concrete is subjected to tension.
And remember that the first values of inelastic strains must be 0 when you enter the values in column in abaqus, so you have to translate the beginning of your coordinate system from 0,0 point to the point ε_el,0.

If you would like to define tensile behaviour as yield stress-displacement, I can explain you what I used.