Investigation of high-performance geopolymer concrete-filled double-skin columns under combined loading conditions

This study investigated the high-performance geopolymer concrete-filled double-skin stainless steel tube (HPGCFDST) columns under concentric, eccentric, and flexural loading conditions. For this, a rational orthogonal array approach was adopted to develop high-performance geopolymer concrete (HPGC) in a previous study. Then, the optimum HPGC mix design was combined with stainless steel tubes, providing significant advantages in harsh marine environments in resisting corrosion and chemical deterioration. Four short columns having a height of 900 mm were tested under different eccentricities to depth ratios (e/D) (0, 0.06, 0.267, and 0.467), and a beam having a length of 1200 mm was also subjected to three-point flexural bending to complete the axial-moment interaction diagram experimentally. Additionally, finite element modelling (FEM) was conducted to simulate the fabricated columns in the experimental program. The results showed an agreement between the numerical and experimental behaviour of the columns. Moreover, the interaction diagram was plotted analytically to assess the capabilities of existing models and accurately predict the results. The experimental findings revealed that the presence of the stainless-steel tubes, which encase the HPGC, improves the ductility of the columns, even though there was a reduction in axial load capacity with increasing the e/D. Local buckling failure was observed at the mid-height of all columns. FEM simulations showed high correlation with experimental outcomes, providing valuable validation for future structural predictions of HPGC-FDST columns.