Hi, 

I am getting this warning from Abaqus:

***WARNING: THE SECONDARY SURFACES ASSEMBLY_CP-120-END_ARCH-8-1 AND 
            ASSEMBLY_CP-122-END_ARCH-8-1 INTERSECT EACH OTHER. THEY ARE PAIRED 
            WITH MAIN SURFACES ASSEMBLY_CP-124-WALLS_GROUND-1 AND 
            ASSEMBLY_CP-126-WALLS_GROUND-1 THAT ALSO INTERSECT EACH OTHER. IF 
            BOTH PAIRS ARE *CONTACT PAIRs, THESE TWO PAIRS SHOULD NOT BE 
            SIMULTANEOUSLY PRESENT IN A STEP BECAUSE OF POSSIBLE CONVERGENCE 
            PROBLEMS; USE *MODEL CHANGE,TYPE=CONTACT PAIR TO REMOVE ONE OF 
            THEM. IF BOTH ARE *TIE PAIRS, THE REDUNDANT TIES WILL BE REMOVED 
            AUTOMATICALLY. IF ONE PAIR IS *TIE AND ANOTHER IS *CONTACT PAIR, 
            REMOVE ONE OF THEM.

In my model, these correspond to two perpendicular surfaces belonging to a 3D arch embedded into a 3D wall (the wall has a pocket to accommodate the arch). The two surfaces are in contact only along a common edge, but they are part of different contact pairs involving different faces of the arch–wall interface.

I initially assumed I needed to define contact for all faces where the arch is in contact with the surrounding wall.

However, Abaqus is warning that the interaction pairs intersect each other, suggesting that some of them should not be defined simultaneously (possibly using *model change or removing one of the contact pairs).

My questions are:

• Is this warning something that can safely be ignored in this type of geometry, or does it indicate a real modelling issue?
• In cases like an embedded arch within a wall (multi-face contact), what is the correct way to define the contact interactions without over-constraining the system?

Any advice or examples from similar modelling situations would be greatly appreciated.