Performance Evaluation of CFST Columns under Biaxial Loading with and without Shear Connectors

Concrete Filled Steel Tube (CFST) columns are advanced composite structural members widely used in modern construction because of their high strength, stiffness, ductility, and ease of construction. These columns consist of hollow steel sections filled with concrete, combining the compressive strength of concrete and tensile strength of steel. The steel tube acts as permanent formwork and provides confinement to the concrete core, while the concrete delays inward buckling of the steel tube. Due to these advantages, CFST columns are increasingly used in multistory buildings, bridges, industrial structures, and earthquake-resistant construction. This research paper presents an experimental investigation on the axial load carrying capacity of circular and square CFST columns with and without shear connectors. Different grades of concrete such as M20, M30, and M40 were considered to evaluate the influence of concrete strength. The test specimens were subjected to axial compression loading using a Universal Testing Machine (UTM). The obtained experimental results were compared with predictions from ACI 318, AISC-LRFD, and Eurocode 4 design standards. The study concludes that higher concrete grades and the use of shear connectors significantly improve the load carrying capacity and ductility of CFST columns. Keywords- CFST columns, composite construction, axial load, steel tube, shear connectors, concrete confinement, Eurocode 4.