Problems with contact simulation

[alegio20]

Hello,
I am a structural engineer who is dealing with contact simulation for the first time and I am having some numerical issue.
My model is made using steel beams and my aim is to evaluate how the structure collapse under certain loads. I have defined a contact using "Penalty" for both normal and tangential behavior (friction coefficient 0.1) and then created a General Contact interation. My analysis is explicit.
However, with gravity loads I am obtaining a deformed shape that I guess is affected by a very close distance among beams and bracings that confuses the contact algorythm. A screenshot is attached.
Also, if I ignore the General COntact Interation, the obtained deformed shape does not have numerical issues and it is the one that I expect under gravity loads.
Can someone helps me understand what is going on with my model?

Thanks.

 

[FEA way]

In Abaqus/Explicit general contact for beam elements works in such a way that contact thickness is calculated as a radius of a circle circumscribed to the actual geometry of the cross-section. What’s more, Abaqus may automatically reduce the contact thickness for structural elements to avoid self-intersections. This may lead to some confusion and issues. Generally you should be very careful with the level of mesh density in such cases.

Also check this thread with similar discussion:

https://www.eng-tips.com/viewthread.cfm?qid=469000