When　a　reinforced　concrete　(RC)　frame　subjected　to　an　edge-column-removal　scenario,　its　floor　system　exhibits　a　complicated　mechanism　against　progressive　collapse　due　to　the　interaction　between　beams　and　slabs　and　the　two-way　load　transfer　characteristics.　In　this　study,　laboratory　tests　of　five　1/3-scaled　RC　frame　substructure　specimens,　including　four　beam-slab　specimens　and　one　beam　specimen　without　a　slab,　are　reported.　The　effect　of　critical　structural　parameters　(i.e.,　the　beam　height,　slab　thickness　and　seismic　reinforcement)　on　the　collapse　resistance　was　investigated　by　analyzing　the　applied　loads,　structural　deformations　and　material　strains.　The　RC　slabs　contribute　to　an　increased　collapse　resistance　of　the　control　beam-slab　specimen　by　146%　under　small　deformations　(i.e.,　the　beam　mechanism)　and　98%　under　large　deformations　(i.e.,　the　catenary　mechanism)　compared　to　the　beam　specimen.　The　resistances　of　the　beam-slab　specimens　were　mainly　provided　by　the　slabs　and　the　beams　in　the　direction　along　the　free　edge,　more　significantly　by　the　portion　close　to　this　edge　where　the　largest　deformation　was　developed.　Increasing　the　seismic　reinforcement　in　the　beams　resulted　in　a　much　larger　collapse　resistance　under　both　beam　and　catenary　mechanisms.　In　contrast,　increasing　the　slab　reinforcement　by　expanding　the　slab　thickness　marginally　improved　the　collapse　resistance　under　the　catenary　mechanism　but　contributed　little　to　that　under　the　beam　mechanism.　Increasing　the　beam　height　also　largely　improved　the　collapse　resistance　under　the　beam　mechanism,　but　had　limited　impact　to　that　under　the　catenary　mechanism.　(C)　2016　Elsevier　Ltd.　All　rights　reserved.