Answer:
A single foundation is rotated by rotating the nodal support in RFEM/RSTAB:
- Open the "Edit Nodal Support" dialog box → select "User-defined axis system: Rotated" → click the [Edit] button.
- Open the "Edit User-Defined Axis System" dialog box → set support rotation as required (see Image 01).
- Recalculate in RF‑/FOUNDATION Pro and display graphic (see Image 02).