To　study　the　failure　mechanism　and　collapse-resistant　mechanism　of　fire-exposed　reinforced　concrete　(RC)　frame　structures,　full-scaled　three-dimensional　finite　element　models　were　developed　based　on　thermal-mechanical　techniques　in　this　study.　After　verifying　the　accuracy　of　the　FE　models,　the　collapse-resistant　performance　of　full-scale　RC　beam-column　assemblies　under　a　middle　column　removal　scenario　during　/　after　elevated　temperature　were　analyzed.　Based　on　the　FE　analyses,　the　effects　of　fire　duration,　the　side　column　subjected　to　fire　and　seismic　detailing　were　discussed.　Furthermore,　the　previous　research　based　on　1　/　2　scale　assemblies　was　used　to　conduct　comparative　study.　The　FE　results　indicate　that　the　first　peak　load　of　the　assemblies　significantly　decreases　during　elevated　temperature　due　to　the　degradation　of　properties　of　rebar　and　concrete.　At　a　fire　duration　of　30　min,　the　failure　mode　of　fire-exposed　assemblies　is　similar　to　that　of　assemblies　in　ambient　temperature,　the　failure　of　assemblies　is　dominated　by　the　fracture　of　beam　rebar　at　the　beam　ends　connected　to　the　middle　column.　When　the　fire　duration　exceeds　60　min,　the　failure　of　assemblies　is　controlled　by　the　fracture　of　beam　top　rebar　at　the　location　of　rebar　curtailment.　The　assemblies　after　high　temperature　can　develop　compressive　arch　action　and　catenary　action　in　sequence　to　resist　collapse,　and　the　ultimate　deformation　capacity　and　load　resistance　capacity　are　similar　to　those　of　assemblies　in　ambient　temperature.　In　addition,　when　the　side　columns　are　exposed　to　fire　for　more　than　60　min　and　then　cooled　down,　they　suffer　compression　failure　under　the　pseudo　static　load.　For　a　fire　duration　of　30-120　min,　adopting　seismic　detailing　can　increase　the　ultimate　load　and　deformation　capacities　of　the　assemblies　after　elevated　temperature　by　51%　and　39%　at　least,　respectively.　©　2024　Science　Press.　All　rights　reserved.