In this research, cold formed steel sections have been used to reinforce and rectify the axial and shear performance of unstiffened, stiffened, L-shaped and T-shaped CFT columns. At first stage, Five L-shaped and Five T-shaped CFT columns, stiffened by various longitudinal internal steel plates and steel pipes subjected to axial and lateral loading, were numerically investigated. The variable study included the shape of CFT columns, various stiffening steel section, and the interaction between stiffening steel and concrete. Primarily FEM procedure had been verified with some available experimental results. The results indicate that the stiffening steel section have a great influence in the performance of L- and T- shaped CFT columns. Also, T-shaped CFT column shows the higher performance in terms of strength, stiffness and ductility than L-shaped section.
At second stage, the base model was CFT column as a benchmark specimen and three new and innovative type of CFT columns with difference in their longitudinal stiffening steel were investigated under axial and cyclic loading. The results show that reinforcement of CFT columns by this method, lead to enhancement in load carrying capacity, enhancement in lateral drift ratio, ductility, preventing of local buckling in steel wall, and enhancement in energy dissipation.
