The predefined sets of simultaneous loads (dead, live, wind, seismic, in various factored ratios) a structural model must be checked against to confirm it's safe under every realistic scenario. A structural model rarely fails under any single load type alone - the dangerous scenarios are combinations, like peak wind load coinciding with full occupancy live load - which is exactly why building codes mandate checking dozens of specific load combinations rather than each load type in isolation, a process modern Revit-to-Robot workflows can automate.