Effect of section shape on the behaviour of thin walled steel columns filled with light weight aggregate concrete: Experimental investigation

The paper presents the results of an experimental investigation to study the behaviour of 19 light weight aggregate concrete-filled steel tubular (CFST) columns subjected to concentric loads. The intermediate CFST columns consisted of 19 different cross-sections. In order to study the most effective section in terms of confinement and stability, All sections were designed to have approximately the same outer perimeter (P), and thus approximately the same cross sectional area, since all sections were manufactured using a mild steel plates with constant thickness. During the experimental tests, the ultimate strength, column shortening, lateral displacement and failure modes were recorded. The results showed that all the CFST columns failed by outward local buckling around the mid-height of the column due to the crushing of the light-weight concrete core, and during the final stages of loading, additional local buckling occurred close to the ends of the column. Furthermore, the results also showed that as the number of steel plates welded together to form the section increases, the section becomes more stable and more confinement can be achieved. Thus, the Octagonal (CO) CFST columns exhibited the largest failure stress followed by the Plus-Shaped (CPS) shaped section. On the other hand, sections formed using a hybridization of the circle and square shapes such as the D-Shaped (CD), Hexagonal Asymmetric (CHA) and Semi- Circular (CSC) showed the lowest failure stress amongst all other section. In terms of ductility, the CFST column with octagon section showed the highest ductile behaviour amongst all other shapes, while the CFST column with L-shaped cross section showed the lowest value of ductility. Also, CFST columns with conventional cross-sectional shapes such as circle and square seem to have a relatively high ductility index. On the other hand, as the shape becomes more irregular, its ductility index decreases.