Behaviour of high-performance alkali-activated slag concrete-filled double-skin steel tubes under compression loading

This study investigates the behaviour of high-performance alkali-activated slag concrete-filled double steel tubular (HACFDST) columns under axial compression. Utilizing high-performance alkali-activated slag concrete (HPAASC) in concrete-filled double steel tubes (CFDST) results in an innovative composite member combining the benefits of both technological domains. HPAASC, a sustainable substitute for conventional concrete, contributes to improved environmental friendliness, while CFDST enhances structural capabilities. Fourteen HACFDST specimens, comprising six circular and eight square sections, were tested to enhance our understanding of the structural performance of HACFDST members through experimental and numerical methodologies. A numerical model was proposed to predict the behaviour of circular and square HACFDST columns under axial compression. The assessment of experimental and numerical findings demonstrates that the proposed numerical model accurately forecasts the behavior of axially loaded HACFDST columns with circular and square sections. Increasing the L/Do or L/B ratio of the specimen results in decreased axial stiffness but enhances ductility. Additionally, beyond peak strength, square HACFDST columns exhibit a sharper decline in strength compared to their circular counterparts. As the L/Do or L/B ratio of HACFDST specimens increases from 2.88 to 7.95, the compressive strength index decreases from 1.28 to 1.2, emphasizing the need to optimize specimen dimensions to maximize the benefits of steel tube confinement.