The behaviour of composite joints continues to be an issue of interest in the area of steel and composite structures. The progress achieved in the programming and computer technology made possible the application of advanced 3D Finite Element Method for the analysis of composite steel concrete frame joints and simulate their real behaviour. The goal of this 3D modelling is to obtain “Load-deflection” curves as close as possible to the ones experimentally obtained, in a practical way and with reduced cost and time. The study presents in detail two illustrative examples created by using 3D FEM for a welded joint and a joint with extended end plate. For both joints, a nonlinear static analysis was applied using ABAQUS commercial code, ver. 6.11 and the obtained results were compared with experimental full-scale composite joints conducted by the authors. The numerical models were created by using 3D finite elements of solid type C3D4R, considering the contact between components and the bolts pre-tensioning. A Concrete damaged plasticity “CDP” model was used for concrete material and a steel damage option based on Gurson's porous metal plasticity theory was used for the steel structure. The analysis focused on the state of stress at each loading step, the failure mode in comparison with the one experimentally observed, and the comparison of the Load-Deflection predictions curves with the ones experimentally obtained.