Experimental study on the axial compressive behaviour of steel reinforced concrete composite columns with stay-in-place ECC jacket

Steel Reinforced Concrete (SRC) column made with high strength materials features excellent load-carrying capacity and energy dissipation capacity, but the compromised ductility issue hinders the widespread application in seismic-prone areas. To overcome this weakness, this paper proposes a novel type of steel-concrete composite column by employing Engineered Cementitious Composites (ECC) as the permanent formwork of conventional SRC column. An experimental program was conducted by subjecting seven stub columns to monotonic axial compressive loading. The test variables in this study include the presence of ECC jacket, the presence of embedded structural steel, stirrup spacing and stirrup configuration. The axial performance were carefully analyzed in terms of load-carrying capacity, initial stiffness, post-peak ductility, damage pattern, as well as the full range load-deformation response. The physical tests confirm the potential of ECC jacket to be used as the permanent formwork of SRC columns as to improve both the construction efficiency and structural performance, and the comparison between the test results and analytical predictions demonstrates the applicability of design equation in EN 1994-11 and JGJ 138-2016 to predict the axial capacity of ECC-SRC columns.