Influence of geopolymer foam concrete on the mechanical performance of cold-formed steel built-up columns

This study aims to improve the bearing capacity and prevent buckling deformation in cold-formed steel (CFS) columns by investigating the utilization of built-up CFS columns filled with geopolymer foam concrete (GFC). The research employs a combination of experimental testing, numerical simulations, and theoretical analysis. The study conducts axial compression tests on various column configurations, including CFS single-limb columns, CFS built-up columns, and CFS-geopolymer foam concrete (CFS-GFC) composite columns. The buckling modes, failure features, bearing capacities, and the bonding effects between GFC and CFS are compared and analyzed. A finite element model is developed and validated against experimental data to investigate key parameters such as slenderness ratio, width-to-thickness ratio, number of solder joints, GFC density grade, stiffening ribs, and their effects on buckling behavior, bearing capacity, and failure mechanisms in CFS-GFC composite columns. Determining the bearing capacity of CFS-GFC composite columns is a complex task, where the study evaluates the bearing capacity based on Chinese (JGJ138-2016 and GB50936-2014), American LRFD, and Japanese AIJ design codes to address this challenge. A calculation method is proposed to accurately determine the bearing capacity of CFS-GFC composite columns under axial compression, with the validity of the formula confirmed through extensive FEM analysis and experimental data.