Error CDP, Plastic strains are negative, help!!

[Nicolas R.]

Hi everyone,

I’m modelling the concrete damage plasticity, I’m trying to define the concrete compression damage and the concrete tensile damage through the damage parameters to each one (see the annex) I’m having the next error message:

DURING THE CONVERSION FROM CRUSHING TO PLASTIC STRAIN Abaqus FOUND NEGATIVE AND/OR DECREASING VALUES OF PLASTIC STRAIN. VERIFY THAT THE DEGRADATION DATA UNDER *CONCRETE Both (COMPRESSION/TENSION) DAMAGE IS CORRECT.

I calculate the plastic strain (through the ecuation defined in the Abaqus Manual) whit the values registers in my model, (see the file adjunct).

Someone can Help me ou explain me why this values of plastic strain are negative if the opened parameters are logical ????

Thanks.

 

[MrusTgr88]

Have you used the formula at the page 23.6.3-6 to calculate the plastic strain? If not, read this section of the Manual.

 

[Nicolas R.]

Hi MRUsTGr88,

I am using the equations presents in the Documentation of the program through the section 23.6.3 Concrete damage plasticity, I do not understand why the both behaviors (compression and tension) provide negatives values of the Plastics Strains (see the annex picture). The trend of the curves has sense in the correctly analysis of the concrete to each behavior, and the damage parameters (dc) and (dt) are bigger according the strains increase.

I'm just ussing a static general step in this analysis, maybe I need to use a Riks Step because the behavior is decresing??

I appreciate any tip!
Regards,

 

[MrusTgr88]

I am not sure, but I think maybe the formula you use for calculation of dc and dt is not good. You have to choose dt and dc so you get positive and rising values for plastic strain.

 

[Nicolas R.]

I am not using a equation to calculate the damage parameter dc and dt, just using the factors implemented by other autor in your researchs, but in their models this is good but when I use it in my model I have this error!! (See the annex)

Any tip, thanks!

 

[MrusTgr88]

I think you are using E=19,7 MPa and you should use 19.7GPa. Or that is what I see from your table (the first one you sent). Correct me if I am wrong.

 

[Nicolas R.]

I forgot to say thank you very much, I´ll never see, now I can continue with my model... Best regards.