This　paper　presents　experimental　and　numerical　investigations　on　the　collapse-resisting　behavior　of　extended　endplate　beam-column　joints　after　high　temperatures.　The　failure　patterns　and　structural　responses　of　extended　endplate　(EP)　joints　after　high　temperature　to　resist　progressive　collapse　were　first　described,　and　then　the　effects　of　fire　temperature　and　temperature　duration　on　their　collapse　resistance　mechanisms　were　also　analyzed　in　detail.　The　test　results　demonstrate　that　all　specimens　withdrew　from　work　owing　to　the　serious　deformation　of　endplate　bolt　holes　or　the　brittle　fracture　of　high-strength　bolts,　resulting　in　the　catenary　mechanisms　of　EP　joints　not　being　adequately　developed.　Compared　with　previous　studies,　it　is　shown　that　the　fire　temperature　exerts　the　most　significant　effects　on　the　carrying　capacities　and　deformability　of　EP　joints,　and　the　collapse　resistance　of　corresponding　assemblies　is　most　sensitive　to　the　fire　temperature.　However,　the　temperature　durations　have　an　insignificant　influence　on　the　development　of　flexural　mechanism　resistance,　especially　for　those　after　600　°C　and　800　°C.　Moreover,　the　corresponding　refined　FE　models　in　consideration　of　the　damage　and　fracture　of　ductile　metals　have　been　established　to　reproduce　the　structural　response　of　specimens　after　high　temperature.　To　improve　the　post-fire　collapse-resisting　performance　of　assemblies,　both　the　lateral　plate　reinforcement　and　welding　reinforcement　methods　were　proposed　and　compared　with　the　assistance　of　validated　FE　models.　From　a　practical　viewpoint,　the　reinforcement　with　lateral　plates　is　determined　as　a　superior　technique　for　post-fire　EP　joints　against　progressive　collapse.　©　2024