When assigning a shell section to a wire, you have the options of mid, top and bottom surface. Is there a way to show what side abaqus is taking as the top surface or how is it defined?
You can’t assign shell section to a wire. Such section can only be assigned to shell type part.
These settings refer to shell offset. It’s a feature that allows you to define offset from the shell midsurface to the reference surface (where nodes are located). Normally this offset is zero so that these two surfaces are coincident but you can change it.
Reference surface (green one in the picture) is basically the surface that you draw and mesh.