Answer:There are two modelling approaches for rating, i.e. one with construction stages and the other without. The model seems to include construction stages for which the program generates the 'Dead Load (CS)' load case, representing the effects of dead loads on the bare steel section. When a model includes construction stages, the Dead Load (CS) is automatically selected as a 'DC (Before)' load case for the Rating function. Thus, there is no need to choose any load case.
This is applicable for AASHTO LRFR-19 & AASHTO LRFR-11 codes only.However, when a model does not include construction stages, the user is supposed to select a static load case for 'DC (Before)'.