Progressive　collapses　are　resisted　by　the　catenary　mechanism　in　reinforced　concrete　(RC)　frame　structures　undergoing　large　deformations.　Research　to　date　has　mainly　focused　on　the　nonlinear　dynamic　progressive　collapse　resistance　demand　of　this　type　of　structures　under　the　beam　mechanism.　(that　is,.　for　small　deformations),　and　that　the　catenary　mechanism　is　lacking.　As　a　first　attempt,　this　study　establishes　a　dynamic　amplification　factor　for　evaluating　the　resistance　demands　of　RC　frames　under　the　catenary　mechanism.　To　achieve　this,　an　energy-based,　theoretical　framework　is　proposed　for　calculating　the　aforementioned　demands.　Based　on　this　framework,　the　analytical　solution　for　the　collapse　resistance　demands　of　regular　RC　frames　under　the　catenary　mechanism　is　readily　obtained.　Numerical　validation　indicates　that　the　proposed　equations　can　accurately　describe　the　progressive　collapse　demand　of　RC　frames　undergoing　large　deformations.