Improving　the　ductility　of　the　structure　to　withstand　local　damage　and　prevent　progressive　collapse　is　critical　for　steel-frame　structures.　In　this　study,　a　novel　principle　of　beam-to-column　connections　was　developed,　which　arranged　openings　at　the　beam　flange　to　form　a　flange-opening　section　(FO).　First,　experimental　investigations　were　conducted　on　two　FO　substructures,　considering　their　deformation　capacity,　failure　modes,　internal　force　evolution,　and　resistance　mechanism　development.　Second,　numerical　simulations　verified　by　experiments　were　conducted　to　further　investigate　the　number　n,　distance　l,　and　diameter　d　of　the　flange　openings,　and　the　results　were　compared　with　those　of　the　case　that　had　no　weakening　of　mechanical　properties.　Third,　because　some　flange　openings　weakened　the　mechanical　properties　of　the　structure,　specimens　with　V-shaped　reinforcing　plates　(FOV)　were　studied.　The　results　indicated　that　the　mechanical　properties　of　the　FO　specimens　increased　with　n,　decreased　with　an　increase　in　d,　and　increased　with　l.　The　mechanical　behavior　of　the　new　beam-to-column　connections　using　flange　openings　and　reinforcing　plates　was　studied　to　relocate　the　plastic　hinge,　realize　a　second　path,　and　successfully　improve　the　progressive　collapse　resistance　of　the　steel　frame　structure.