Design of confinement reinforcement for encased composite columns

•This paper examines the efficiency of the confinement requirements among three selected specifications (ACI Specification, AISC Seismic Specification, and Taiwan encased composite building code) for designing encased composite columns.•The analysis of this study identifies major parameters that are omitted from the current confinement requirements for encased composite columns.•This paper proposes new confinement equations for encased composite columns. The proposed requirement correlates well with the flexural performance of the encased composite columns, warranting a consistent degree of safety for the range of properties studied.•The proposed confinement equations significantly reduce the amount of required transverse reinforcement, relieving the challenges in detailing seismic hoop reinforcement around the structural steel core.