For the steel angle section showed in attached picture, as compression member, around axis 1, it should consider slenderness radio. Does STAAD Pro consider it also? Could you explain the detail on it? Thanks
Yes single angles in STAAD.Pro are designed with respect to the principal axes as required by many country codes. Certain codes like the AISC 360 do permit designing the single angles with respect to geometric axes under certain conditions and those are implemented too.