Answer:
The reason for the different results is likely the settings of effective lengths for the stability analysis. According to the default setting, these are determined automatically in the RF‑/CONCRETE Columns add-on module. However, this method does not work for divided members, and thus no stability analysis is performed (a corresponding warning message appears).
If you have entered the effective lengths manually, this only applies to a single member. In order to perform correct stability analysis of the column as an entire structural component, it is necessary to define it as a set of members.
