Axial compressive performance of high-strength spiral-confined high-strength concrete-filled high-strength square-steel-tube long columns

High-strength spiral-confined high-strength concrete-filled high-strength square steel tube (HSS-CHCFHSST) columns are a novel type of composite column. Embedding high-strength spirals (HSS) can improve the ductility of high-strength concrete-filled high-strength square steel tube (HCFHSST) columns. This study aims to evaluate the fundamental performance of HSS-CHCFHSST long columns under axial compression. A series of tests were conducted on axially compressed HSS-CHCFHSST long columns. The strength of the concrete (fc') was 90 MPa. The maximum yield strengths of the steel tubes and spirals were 818 MPa and 1561 MPa, respectively. The finite element model of HSS-CHCFHSST long columns was also established. The results indicate that after reaching peak load, HSS-CHCFHSST long columns with a slenderness ratio of less than 27.71 exhibit deformation and ultimately fail during testing. As the slenderness ratio increases from 13.86 to 55.43, there is a corresponding decrease in axial compressive capacity by 28.74 %. When the slenderness ratio exceeds 40, the beneficial effect of HSS on enhancing ductility in HCFHSST long columns becomes minimal. Regression analysis was used to propose equations predicting the stability capacity of HSS-CHCFHSST axial compression columns, and their applicability was validated by comparison with experimental data and finite element analysis.