Fire　is　one　of　the　accidental　loads　that　can　cause　progressive　collapse　of　buildings.　However,　the　behavior　of　fire-exposed　reinforced　concrete　(RC)　frames　to　resist　progressive　collapse　are　still　unclear.　Therefore,　a　numerical　study　on　the　RC　assembly　based　on　the　sequential　thermal-mechanical　coupling　method　is　conducted.　Fire　effects　on　the　failure　mode,　load-resistant　capacity,　and　the　evolution　of　load-resistant　mechanisms　of　the　RC　frame　are　captured.　The　numerical　results　show　that　compressive　arch　action　(CAA)　and　catenary　action　(CA)　can　develop　in　sequence　for　the　specimens　exposed　to　fire　within　a　short　fire　duration　of　30　min.　The　failure　of　the　specimen　is　controlled　by　the　fracture　of　beam　rebars　near　the　removed　column.　However,　when　the　fire　duration　exceeds　60　min,　the　specimen　is　difficult　to　develop　effective　CA　due　to　a　decrease　of　over　80%　in　the　tensile　strength　of　the　bottom　reinforcement.　The　failure　of　the　specimen　is　dominated　by　the　fracture　of　the　rebar　at　the　cut-off　point　of　the　beam　top　rebar.　Fire　lasting　for　30　min,　60　min,　90　min　and　120　min　results　in　a　decrease　of　41%,　72%,　77%　and　78%　in　ultimate　load,　respectively.　Increasing　the　span-depth　ratio　can　upgrade　the　deformation　capacity　of　the　specimen,　but　it　is　adverse　to　the　development　of　CAA.　The　effects　of　the　rein-forcement　ratio　on　the　failure　mode,　the　ultimate　load　and　deformation　capacity　are　mild　as　the　fire　exposure　duration　increases.