Steel　frame　structures　with　ordinary　weld　connections　often　suffer　from　brittle　fractures;　to　mitigate　this　issue,　measures　have　been　taken　to　integrate　plastic　hinges　and　improve　the　ductility　of　the　steel　connections.　A　new　reduced　beam　section　(RBS)　connection,　consisting　of　radius　cuts　in　the　beam　flanges　and　circular　openings　in　the　beam　webs,　is　proposed　to　allow　for　more　ductile　connections.　RBS　connections　may　increase　structural　deflection　and　crack　width　in　the　steel　frame　structure　under　large　deformations.　Therefore,　it　is　extremely　important　to　consider　the　bearing　capacity　and　progressive　collapse　resistance　of　steel　frame　structures　with　RBS　connections.　In　this　study,　nine　different　specimens　with　double-span　frames　were　constructed　and　tested　under　a　central　column　removal　scenario:　one　without　an　RBS　(RBS0),　one　with　flange　reductions　(RBS1),　and　seven　with　web　and　flange　reductions　(RBS2).　The　mechanical　behaviours　of　the　different　specimens　were　determined,　including　their　failure　modes,　vertical　force-deformation　responses,　and　contribution　of　catenary　action　to　resist　progressive　collapse.　The　results　indicated　that　the　RBS0　specimen　with　brittle　failure　did　not　effectively　resist　progressive　collapse.　RBS1　exhibited　superior　ductility　and　resistance　compared　to　RBS0;　however,　its　resistance　to　progressive　collapse　after　cracking　required　further　improvement.　RBS2　with　web　openings　formed　an　arch　structure　to　dissipate　energy　through　continuous　deformations.　Further,　two　important　factors　in　RBS2　that　influenced　its　mechanical　properties　were　the　diameter　and　the　distance　of　the　web　opening,　which　were　related　to　the　development　of　arching　and　catenary　action.　(C)　2020　Elsevier　Ltd.　All　rights　reserved.