Experimental and Numerical Study of Octagonal Composite Column Subject to Various Loading

In this study, experimental tests of the behaviour of steel and partially encased composite (PEC) columns subjected to compressive loading is performed. Evaluation of this type of composite column under axial loading and numerical analysis of its behaviour under combined torsional and axial loading are the main objectives of this study. At first, a parametric study of PEC columns under axial loading was performed in order to find the relationship between flange slenderness ratio of steel column section and concrete confinement. Width-to-thickness ratio of the flange, diameter and spacing of the transverse links were considered as variables in this study. It was observed that dimension of transverse links had almost no effect on the capacity of the specimens, however smaller transverse links spacing increased both capacity and deformability of the specimens. The comparison of the code equations given in CSA S16-14 and EN 1994-1-1 revealed that the equation in CSA S16-14 underestimates the capacity. Furthermore, different types of retrofit of cross-shaped steel column including concrete encasement, use of stiffener plates and transverse links were investigated in this research. Results revealed that concrete confinement and use of transverse links had respectively the most and the least effect on increasing torsional capacity of the specimens.