Interaction buckling of concrete filled columns using high strength steel

In Australia the use of thin walled steel sections coupled with concrete infill has been used on various building projects with great advantage. The major advantages of the use of thin-walled steel sections are the reduced structural steel costs and the economy in construction that the method provides. The few international standards for composite structures are limited to the design of concrete filled steel columns with compact sections, however there is no research work in the literature available concerned with slender concrete filled thin-walled steel columns. This paper presents both an experimental and theoretical treatment of coupled local and global buckling of concrete filled steel columns sometimes termed interaction buckling. A numerical model is developed in order to study the behaviour of slender concrete filled steel columns incorporating material and geometric non-linearities. For this analysis the equilibrium of the member is investigated in the deformed state, using the idealized stress–strain relationships for both materials steel and concrete, considering the elastic and plastic ranges. The experimental results of column with high strength steel casings conducted herein by the authors are used for comparison. The effect of the confined concrete core is also addressed and the method shows good agreement with the experimental results of concrete filled steel columns with compact sections. The behaviour of concrete filled steel slender columns affected by elastic or inelastic local buckling is investigated and calibrated with relevant experimental results. The paper then concludes with a design recommendation for the strength evaluation of slender composite columns using high strength steel plates with thin-walled steel sections.