To explore the structural performance of axially loaded high-strength concrete-filled square steel tubular (HCFSST) long columns, a total of nine HCFSST specimens with various slenderness ratio (λ) values were experimentally tested and the working mechanism of the column was numerically revealed in this work. Parametric studies were also conducted to explore the column stability behavior, material strength matching relationship, and internal load distribution of each material. Combined with test results, various buckling curves (a₀, a, b, c, and d) specified in code EC3 were reviewed to confirm an appropriate design curve for HCFSST columns. Furthermore, the predictions of the stability reduction factors and peak-loads of columns based on current design codes were compared and discussed. The results indicated that the failure modes of the columns were significantly affected by the λ values. To efficiently improve the load bearing performance of the column, the recommended value of f_y/f_cu ratio is within 6.57–7.00 as λ = 14–37 and is within 5.75–6.57 as λ > 37. The new design models of the axially loaded columns proposed in this work are applicable to the HCFSST columns and hence are recommended. This study will provide guidance for the engineering practice of HCFSST columns.

为探究轴载高强方钢管混凝土（HCFSST）长柱的结构性能，对9个不同长细比（λ ）值的HCFSST试件进行了试验测试，数值揭示了柱的工作机理。在这项工作中。还进行了参数研究，以探索每种材料的柱稳定性行为、材料强度匹配关系和内部载荷分布。结合试验结果，各种屈曲曲线（a ₀、a、b、c 和 d) 代码 EC3 中指定的内容经过审查，以确认 HCFSST 柱的适当设计曲线。此外，对基于现行设计规范的柱稳定性降低因子和峰值载荷的预测进行了比较和讨论。结果表明，柱的失效模式受λ值的显着影响。为有效提高立柱的承载性能，f _y / f _cu比的推荐值在 6.57-7.00 之间（λ  = 14-37）和 5.75-6.57 内（λ ） > 37. 本文提出的轴向荷载柱的新设计模型适用于 HCFSST 柱，因此被推荐。本研究将为HCFSST柱的工程实践提供指导。