Learning Forum

[mostafam]

Hi

My model consists of 2 solid parts where on the sharing nodes I applied constrained_node_set. But the analysis shows that this constarined is not been applied and I see the separation occurs. Any idea why this is happening?

I don't set any death time for the constrained or something like that.

I appreciate any help.

 

Thanks

[Armin]

Hi Mostafa,

Here are some suggestions:

Assuming that your parts are flexible (not rigid), separation on the sharing nodes may occur if the nodes included in the set are subjected to other constraints, including prescribed motion using *BOUNDARY_PRESCRIBED_MOTION. 
Also, it is important to verify that the constrained nodes are not set to become inactive at a certain failure time as this would allow the nodes to move freely after the specified time. This is defined using the parameter TF of the *CONSTRAINED_NODE_SET card.

[mostafam]

Hi Armin,

Thanks for the suggestions.

I checked all of them and the problem was not found.

I have used this command a lot in my previous analysis, and it works perfect. Even I tried to have a simpler model and checked it again, it was working. But the geometry that I have is a curved structure on top of a pair of foundation where cause such problem. 

[mostafam]

Actually, now I found where the problem was.

My structure was reinforced concrete and I used COMSTRAINED_BEAM_IN_SOLID for the interaction between concrete and rebar elements. At the bottom of the structure I was applying those constrained_node_set and because there were more than 2 constraints for some of thwe elements, that would make problem for me.

Thank you so much for the hint.

Now I am thinking of having an interestrial element (part) in between and do the rest, but by any chance is there a better way to have two types of constarints on an element?

Thanks

[Armin]

No problem, Mostafa, I'm glad it was helpful. I don't have much experience with reinforced concrete so I would suggest that you post your new question as a new post in the LS-DYNA channel of this forum.