The CFDST (concrete-filled double-skin tubular) columns consist of concentric steel tubes with concrete filling between them and have a lower self-weight compared to other configurations of composite columns. Double-skin columns provide good structural performance, even when subjected to seismic activity, explosions, and dynamic loads. Although existing codes do not cover these columns' design, with the advancement of research, they have been increasingly used in offshore support structures, transmission towers, bridges, footbridges, and tall buildings. This article describes the experimental tests on the cross-section behaviour and resistances of six composite double-skin prototypes (CFDST) composed of a stainless steel outer circular tube, a carbon steel inner circular tube, and conventional concrete with a compressive strength of 30 MPa between them, subjected to concentric and eccentric loads and pure bending. The prototypes were defined based on parameters already adopted in the literature. The columns' resistance values of the tests were predicted using the M-N interaction diagram. The obtained results are in accordance with the formulations proposed in the literature.