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Recently concrete filled steel tubular columns developed in the construction industry. In these types of columns, concrete and steel have efficient and complementary performance because of proper confinement provided by steel tube for concrete which leads to increase strength and ductility of concrete, also concrete prevents local and inward buckling of steel tube. CFST columns have several advantages over conventional reinforced concrete columns such as elimination of formwork and reinforcement, rapid construction, decrease in the column dimensions and saving extra floor space and also improvement in the load-carrying capacity, ductility and energy absorption ability. Despite the above... 

In recent years use of concrete filled steel tube column structures has been increased due to their several advantages. In these columns the steel tube provides confinement for the concrete core of the column, so it increases axial strength and flexibility of the concrete core, and prevents spalling of the concrete. On the other hand the concrete core delays the local buckling steel tube and increases its bearing capacity. In addition, these columns have higher stiffness and strength than typical concrete columns due to placement of steel in farthest point of column cross section. The steel tube besides its structural role acts as framework for the concrete core and reduces time and cost of... 

concrete-filled steel tube offers many practical advantagescompared withconventional structural systems. The concrete infill provides stiffness and strength in compression and restrains local and global buckling. The inelastic deformation capacity of the CFT system is increased by the confinement of the concrete fill by the thin, ductile steel tube, and this significantly contributes to the seismic performance.
In this research, Formation and development of plastic hinges in CFST frames using pushover analysis was investigated. Different frames with rectangular and circular column and I beam weredesigned and Using nonlinear finite element analysis, interaction between steel and concrete...