Under　a　penultimate　column　removal　scenario,　the　critical　sub-frame　is　in　an　asymmetrical　boundary　condition.　In　that　case,　the　sub-frame　suffers　a　higher　risk　of　collapse.　To　study　the　effects　of　asymmetrical　boundary　conditions　on　the　progressive　collapse　behavior　of　reinforced　concrete　(RC)　frames,　three　1/2-scale　RC　beam-column　assemblies　subjected　to　the　penultimate　column　removal　scenario　were　tested　with　Pushdown　loading.　The　effects　of　seismic　design,　non-seismic　design　and　sectional　dimension　of　the　column　on　the　load　resistance,　failure　mode　and　conversion　of　the　load-carrying　mechanism　were　studied.　Test　results　indicate　that　seismic　design　allows　the　sufficient　development　of　catenary　action,　resulting　in　higher　load　resistance.　The　exterior　joint　of　the　assemblies　has　sufficient　shear　strength　to　prevent　shear　failure　regardless　considering　seismic　design　or　not,　which　allows　the　failure　of　the　assemblies　to　be　controlled　by　the　fracture　of　the　beam　rebar.　In　addition,　the　effects　of　longitudinal　reinforcement　diameter,　sectional　dimension　of　the　column　and　transverse　reinforcement　ratio　of　the　joint　were　studied　with　the　finite　element　software　LS-DYNA.　It　is　found　that　enlarging　the　longitudinal　reinforcement　diameter　can　increase　the　load　resistance;　however,　the　resulting　greater　horizontal　tension　can　lead　to　the　large　eccentric　compression　failure　of　the　column.　Increasing　the　sectional　dimension　of　the　column　has　a　slight　effect　on　load　resistance.　©　2024　Tsinghua　University.　All　rights　reserved.