Answer:
The PLATE‑BUCKLING add-on module allows you to only calculate rectangular buckling panels.
You can enter the panel in Window "1.1 General Data" of the add-on module (see Image 01). As an alternative, you can also specify the panel from an existing RFEM 5 or RSTAB 8 file in the dialog box where you graphically assign the respective c/t-part (see Image 02).
