This　paper　provides　a　simplified　analytical　model　for　the　restrained　steel　beam-column　substructure　under　a　fire-induced　progressive　collapse　scenario,　which　is　applied　to　predict　the　collapse　resistance　of　substructures　under　fire.　The　simplified　model　is　formulated　for　axially　and　rotationally　restrained　two-span　steel　beam-column　substructures　under　column-loss　scenarios　and　involves　rigid　and　semi-rigid　connections.　The　response　characteristics　of　restrained　substructures　exposed　to　fire　under　column-loss　scenarios　in　each　response　stage　are　elaborately　analyzed.　A　＇negative＇　catenary　stage,　in　consideration　of　the　unique　negative　axial　force　effects　induced　by　the　temperature　thermal　expansion,　was　first　introduced　in　the　five-stage　simplified　model　for　restrained　substructures　exposed　to　fire　against　progressive　collapse.　Subsequently,　the　explicit　calculation　formulas　for　determining　the　vertical　loads　and　deflection　of　both　rigid　and　semi-rigid　joint　substructures　exposed　to　fire　were　derived　in　a　quantified　way,　based　on　rigid-plastic　mechanisms　and　restraint　coefficient　methods.　In　addition,　the　corresponding　numerical　simulation　analysis　on　a　restrained　two-span　steel　beam-column　substructure　with　different　end　constraints　and　fire　conditions　was　carried　out　to　verify　the　applicability　and　reliability　of　established　theoretical　formulas.　Comparisons　of　vertical　load-deflection　relationships　between　the　calculation　formulas　and　corresponding　numerical　simulation　shows　good　accuracy.　For　more　accurate　prediction　results,　the　error　analysis　was　further　conducted,　and　several　theoretical　formulas　were　modified,　which　were　verified　to　be　accurate　and　reliable　after　correction.　With　derived　resistance　functions,　the　resistance　of　steel　beam-column　substructures　in　fire-induced　progressive　collapse　scenarios　can　be　predicted.　©　2024