In　this　paper　high　fidelity　solid-element-based　numerical　models　are　used　to　study　the　progressive　collapse　resistance　of　reinforced　concrete　(RC)　beam-slab　substructures.　This　is　a　common　type　of　system　used　in　RC　framed　structures　through　monolithic　construction.　After　careful　calibration　of　model　parameters,　the　numerical　models　are　validated　through　comparisons　with　test　data　and　further　employed　to　investigate　the　load　transfer　mechanisms　and　explore　parameters　affecting　the　robustness　of　RC　beam-slab　substructures　under　perimeter　column　removal　scenarios.　The　parameters　studied　include　lateral　restraint　stiffness　at　the　substructure　boundaries,　loading　schemes　in　testing,　slab　thickness　and　reinforcement　detailing　in　slabs.　The　simulation　results　show　that　the　progressive　collapse　resistance　of　the　RC　beam-slab　substructures　is　developed　primarily　through　compressive　arch　action　of　the　longitudinal　beams　and　flexural　mechanism　of　the　transverse　beam　at　small　deflections　and　catenary　action　of　beams　as　well　as　tensile　membrane　action　(TMA)　of　slabs　at　large　deflections.　The　slabs　enhance　structural　resistance　through　working　compatibly　with　beams　as　L-　and　T-section　＂composite　beams＂　at　hogging　moment　regions　and　developing　TMA.　If　the　slabs　are　just　simply　converted　into　equivalent　flanges　of　beams,　the　resistance　at　large　deflections　will　be　significantly　underestimated.