Should the elastic surface foundation of the contact stresses Sigma-z be relative to a global or a local coordinate system?
The elastic surface foundations are always relative to the local coordinate system.
You can display the local coordinate systems by using the context menu. To do this, right-click a surface and select "Local Axis Systems on/off".
Structural engineering software for finite element analysis (FEA) of planar and spatial structural systems consisting of plates, walls, shells, members (beams), solids and contact elements