Moment Concentration at corner of structure in plaxis 2D

That's really normal with these corners. 

In Modeling Yeap

but in reality you think you will see such moment there?

Yes, definely. You have a earth pressure from sides and a foundation on the bottom (if we speak in terminology of structural engineers). The sides will try to deform into the center, however, the foundation will try to hold it in place. This creates shear and eventually, moment. This is why we use near-circular tunnels in design, to avoid stress concentrations.

i posted this subject in another way too(i dont know if you see that)
if I model structure with cluster element rather than beam element stress concentration will significantly decreased( i model elastic cluster with a beam element at center line having factor of 1e-8 for its stiffness (to not double the stiffness) in order to read force and  moment in structure)

you have any idea this way is correct or not?

Let's move on to that subject. I saw that post and found that really weird.

Let's move on to that subject. I saw that post and found that really weird.