Considering　that　the　direction　of　bending　moment　at　the　beam　end　nearby　the　removed　column　will　reverse,　which　may　disagree　with　the　profile　of　prestressing　strands.　Thus,　the　prestressed　concrete　frame　may　have　high　vulnerability　for　progressive　collapse.　In　this　study,　experimental　and　numerical　studies　were　performed　to　study　the　performance　of　unbonded　prestressed　concrete　(PC)　beam-column　sub-assemblies　subjected　to　a　penultimate　column　removal　scenario　to　resist　progressive　collapse.　Two　half-scale　PC　beam-column　sub-assemblies　with　different　strand　profiles　were　tested　by　Pushdown　loading　procedure.　Failure　modes,　the　involution　of　load　resisting　mechanisms,　and　ultimate　load　resistance　were　analyzed.　To　quantify　the　effect　of　the　strand,　a　non-prestressed　reinforced　concrete　beam-column　sub-assembly　was　designed,　the　geometrical　dimension　and　reinforcement　ratio　of　which　were　consistent　with　the　PC　beam-column　sub-assemblies.　It　is　found　that　the　presence　of　the　strand　leads　to　a　greater　load　resistance,　lower　deformation　capacity　and　different　failure　modes.　The　considerable　tension　in　the　strand　cause　significant　second-order　effects　in　the　side　column,　leading　to　large　eccentric　compression　failure.　To　further　study　the　performance　of　PC　frames　against　their　progressive　collapse,　high-fidelity　numerical　models　built　by　LS-DYNA　were　used　to　conduct　a　series　of　parameter　studies.　It　is　found　that　prestress　forces　can　increase　compressive　an　arch　action.　The　strand　can　significantly　enhance　the　ultimate　load　resistance　at　a　large　deformation　stage.　©　2023　Tsinghua　University.　All　rights　reserved.