The columns of concrete filled tubes (CFT) are composed of a steel tube filled with concrete. The concrete core adds rigidity and compressive strength to the tubular column and reduces the potential for internal internal buckling. In contrast, the steel tube acts as longitudinal and lateral reinforcement for the concrete core, which helps to withstand tension, bending moment and shear and provides confinement for concrete.
Due to the benefit of the composite action of the two materials, CFT columns provide excellent structural properties resistant to seismic events, such as high strength, high ductility and high energy absorption capacity. In addition, circular hollow sections have many advantages over open sections, including aesthetic appearance and material cost savings.
Due to the complexity of the connections between steel beams and circular hollow sections, their use in steel structures is limited. This is because the use of standard screwing is not feasible and costly unpopular welded connections are the normal solution.
The concrete filled steel tube columns (CFT) combine the advantages of ductility, usually associated with steel structures, with the rigidity of a concrete structural system.