Concrete　filled　steel　tubes　(CFST)　can　fully　utilize　the　advantages　of　both　steel　and　concrete　to　achieve　superior　ductility　and　strength.　Therefore,　an　increasing　number　of　CFST　members　are　used　as　truss　chords　in　bridge　construction　in　earthquake　zones.　However,　due　to　concrete　settlement,　concrete　shrinkage,　and　temperature　shift　during　service　life,　spherical-cap　gaps　may　exist　inside　CFST　chords,　which　will　have　an　unfavorable　influence　on　the　seismic　behavior　of　the　web-chord　connections.　In　this　study,　the　hysteretic　behavior　of　steel　tubular　T-joint　with　concrete-filled　bottom　chord　with　spherical-cap　gap　is　experimentally　investigated.　A　total　of　24　T-joint　specimens　were　tested　with　the　CFST　chord　under　the　constant　tensile　load　and　the　steel　tubular　web　subjected　to　cyclic　bending.　The　main　testing　parameters　included　spherical-cap　gap　ratios,　chord　to　web　diameter　ratios,　and　chord　diameter　to　thickness　ratios.　Based　on　the　test　results,　the　failure　modes,　hysteretic　response,　load-carrying　capacity,　stiffness　degradation,　ductility　and　energy　dissipation　characteristics　were　investigated　and　analyzed.　The　effect　of　spherical-cap　gap　on　the　hysteretic　behavior　of　CFST　T-joints　was　compared　and　discussed.　The　outcome　of　this　research　is　expected　to　provide　reference　to　the　evaluation　of　seismic　safety　of　CFST　truss　structures.