Behaviour and design of hexagonal concrete-filled steel tubular short columns under axial compression

Concrete-filled steel tubular (CFST) columns have frequently been utilised in the construction of mid-rise and high-rise buildings as they offer smaller cross-sectional size to load carrying capacity ratio than ordinary reinforced concrete or steel solutions. The steel tube component of CFST columns can be shaped into different forms to further increase its strength and this article focuses on hexagonal CFST short columns in compression. Firstly, the literature is revised and it was found that the available experiments on the hexagonal columns cover relatively limited hexagonal dimensions and material properties. Additionally, existing design models were observed to be inaccurate for certain diameter-to-thickness (D/t) ratios of the columns. Accordingly, this paper intends to widen the available pool of data and proposes a new design model to design hexagonal CFST short columns in compression. This is made herein through comprehensive finite element (FE) models by using Abaqus software, carefully validated against experimental results and subsequent parametric studies covering a wide range of hexagonal dimensions of regular cross-section (circular-like). The effect of various D/t ratios, material steel grades and concrete compressive strengths (fc′) on both the behaviour and strength of the hexagonal CFST short columns is investigated. Based on observations made and conclusions drawn upon analysing numerical data generated, a new design model is presented which provides better strengths compared with available design models and with accurate predictions for the full range of D/t ratios.