Concrete　Filled　Steel　Tubular　(CFST)　K-joints　employed　for　truss　structures　gained　high　interest　in　the　last　years　due　to　their　widespread　use　in　engineering　practice.　The　overall　performances　of　these　joints　can　be　efficiently　improved　by　using　steel　studs　welded　in　the　inner　surface　of　the　steel　chord　filled　with　the　concrete,　avoiding　punching　shear　failure,　and　improving　the　overall　strength　and　ductility.　However,　a　reliable　prediction　of　the　structural　behavior　of　the　joints　is　outmost　of　importance　for　the　assessment　of　the　capacity　of　new　and　existing　structures,　and　there　are　no　standardized　design　methods　nowadays.　In　this　paper,　the　structural　performances　of　CFST　K-joints　with　and　without　steel　studs　are　investigated　by　Finite　Element　Modelling　(FEM)　approach　with　the　aim　to　provide　a　predictive　tool　for　the　design.　A　comprehensive　discussion　of　the　key　parameters　that　govern　the　FEM　procedure　as　well　as　the　calibration　of　the　FE　models　was　provided　to　give　the　basis　for　a　reliable　modelling　of　CFST　K-joints　with　and　without　studs　for　the　predictions　of　the　load-displacement/strain　response　and　the　strength,　considering　the　main　failure　mechanisms.　In　this　context,　in　addition　to　the　detailed　FEM　of　CFST　K-joints　with　steel　studs,　a　simplified　equivalent　FEM　approach　is　proposed　to　reduce　computational　effort　keeping　the　same　accuracy.