Answer:
When designing general cross-sections in the RF‑STEEL AISC add-on module, a "Non-designable" message is given for the design ratio. General cross-sections are defined in the program as user-defined sections or shapes which are not included in the specification. Though, some user-defined cross-sections can be designed under specific conditions. The warning message is displayed because shear buckling is not provided for general cross-section in the AISC 360‑16 [1] Chapter G. More info on this topic can be found in the RF‑STEEL AISC manual linked below.
This warning can be turned off in RF‑STEEL AISC add-on module under the "Details" button → Shear Buckling → "Shear buckling warning for general cross-section."
