To　investigate　the　influences　of　different　detailings　on　the　behavior　of　multi-cavity　mega-bifurcated　concrete　filled　steel　tubular　(CFST)　beam-columns　designed　based　on　the　China　Zun　project　in　Beijing,　two　specimens　with　a　1/10　reduced　scale　of　multi-cell　mega-bifurcated　CFST　beam-columns　were　designed.　Specimen　BEC　was　a　standard　reduced-scale　prototype　of　the　beam-columns,　and　specimen　SEC-2　was　that　with　enhanced　flexural　rigidity　of　the　lower　part　compared　with　specimen　BEC.　Several　factors　including　failure　modes,　distribution　of　deflection　along　height,　vertical　load-displacement　and　skeleton　curves,　and　plane　cross-section　assumption　were　examined,　and　the　influence　of　detailings　on　the　performance　of　the　two　specimens　were　investigated　via　tests.　A　nonlinear　computer　algorithm　was　developed　based　on　fiber　models.　The　stress-strain　relationship　of　steel　was　elastic-perfectly　plastic　model.　The　models　considered　for　the　concrete　core　included　that　stipulated　in　the　GB　50010-2010　＇Code　for　design　of　concrete　structures＇　(GB　model)　as　well　as　the　Hu＇s　model　and　Han＇s　model.　Using　the　elastic-perfectly　plastic　model　for　steel,　the　results　show　that　the　GB　model　and　the　Hu＇s　model　have　poor　consistency　with　the　moment-curvature　curves　considering　flexure　second-order　effect　(P-δ　effect),　but　the　Han＇s　model　has　a　good　agreement　with　them.　To　study　the　composite　confinement　effect　of　the　diaphragms　and　multi-cavity　steel　tube　at　the　compressive　zone,　the　modified　Han＇s　models　were　used　for　computing　the　moment-curvature　curves,　where　a　good　agreement　with　the　peak　value　of　the　moment-curvature　curves　considering　P-δ　effect　was　achieved,　although　the　predicted　moment　at　the　descending　stage　was　slightly　lower.　©　2018,　Editorial　Office　of　Journal　of　Building　Structures.　All　right　reserved.