Meaning of symbols

[strozy]

Hi, could someone please explain the meaning of the red lines obtained after meshing the slab

[Gazes]

These are "kinematic constraints" created automatically during "Generation of computational model".
I understand that you calculated your model before (re)meshing the slab.
You can ignore this as it is just visual effect. "Kinematic constraints" are re-created (deleted and created again) during "Generation of calculation model".
To eliminate this effect either:
- switch off "Kinematic constraints"
or
- run "Generation of calculation model" or "Calculations"

[strozy]

Thanks Gazes