Experimental study on axial compression behavior of RAC-encased RACFSST composite columns with high-strength concrete

Abstract

The purpose of this work is to investigate the axial compression behavior of recycled aggregate concrete-encased recycled aggregate concrete-filled square steel tube (RAC-encased RACFSST) composite columns made using high-strength concrete. Therefore, a total of five specimens were made for conducting an axial compression test until failure. The experimental parameters included the coarse aggregate type, stirrup spacing, wall thickness of steel tube, and the existence of cross-tie bars in the square steel tube. The failure mode, load-displacement curves, load-strain curves, and ductility of the composite columns were obtained. An analysis was conducted on the impact of various parameters on the mechanical performance of RAC-encased RACFSST composite columns. The results show that the failure modes of composite columns are comparable. The inclusion of RAC enhances the load-bearing capacity ability of the composite column, but it negatively affects its ductility and deformation capacity. Increasing the wall thickness of a steel tube and reducing stirrup spacing significantly improves the axial compressive mechanical performance of composite columns, which are mainly reflected in axial compressive capacity and ductility respectively. Placing the cross-tie bars inside a square steel tube can improve the load-bearing capacity and deformation capacity. The axial bearing capacity of the composite columns in this study and other research is determined by using existing codes. The computed results are highly consistent with the experimental data.