Effects of loading regimes on the structural behavior of RC beam-column sub-assemblages against disproportionate collapse

•Failure modes of RC beam-column sub-assemblages under progressive collapse were affected by loading regimes.•Load resisting mechanisms of RC sub-assemblages under different loading regimes were compared and discussed.•Structural resistance against progressive collapse was decomposed at different loading stages.•Analytical models were proposed and compared for assessing catenary action capacity of RC frames.