Behaviour and design of eccentrically loaded CFST columns with high strength materials and slender sections

Abstract High strength concrete-filled steel tube (CFST) columns have been adopted in many constructions requiring great load-carrying capacities, large floorplans, cost-effective and time-saving solutions such as modern skyscrapers or high-rise buildings, but their performance is still insufficiently understood due to the lack of experimental investigations and design specifications. The test program in this study consists of eight stub square CFST columns fabricated from high strength materials and slender sections which are beyond the permitted limits specified by many current design provisions. The failure patterns, load and moment resistances, load-mid-height deflection and load-axial strain responses were used to evaluate the overall performance of the test specimens. Furthermore, a numerical model for CFST columns, taking into account the actual factors such as the confinement on concrete cores, initial imperfections and residual stresses on steel tubular members, was developed and demonstrated a good agreement with the experimental results. A parametric study then adopted this verified model to explore the confinement effect on concrete cores and the influence of various material strengths, eccentricity ratios, section slendernesses and member slendernesses on the performance of composite columns. Finally, the load-moment interaction curves of specimens under different loading conditions obtained from experiment and numerical analysis were compared to the predictions of AISC 360-16, Eurocode 4 and AS/NZS 2327 for validating these specifications. In short, this study is expected to advance the understanding in the area of eccentrically loaded CFST columns with high strength materials and slender sections.