Answer:
RSBUCK does not calculate any effective length factors of sets of members. You can only take the results of the individual members as a starting point in this case. You can consider the member for which the smallest critical buckling load Ncr is displayed as governing for the set of members.
It can also be helpful to consider the axial forces in the individual members. If they are the same throughout the set of members with an unchanged cross-section, the effective length factors are also the same. This value can then also be used for the set of members.
