Eccentric behaviour of square CFST columns strengthened using square steel tube and high-performance concrete jackets

•Eccentric behavior of square CFST columns strengthened with steel tube and high-performance concrete jackets was investigated.•The differences in performance of retrofitted columns with various types of concrete jackets were presented and the reasons were elaborated.•Detailed analysis of the load-lateral deflection curve, interaction and stresses of four components throughout the entire process was performed.•The various strengthening designs were compared in terms of load-bearing capacity and ductility.•The calculated capacities of retrofitted columns under eccentric load based on the EC4, GB50936, and AISC 360 codes were compared.