This study examines the performance of 26 concrete-filled steel tube square stub columns strengthened with square steel tube and concrete jacket, 21 steel tubes were infilled with high-performance concrete (HPC) jackets and 5 were infilled with ordinary concrete (OC). The test results of the failure modes, load–axial shortening curves, ductility index, and strain analysis revealed that no evident effect was observed on the load-bearing capacity when steel fibre-reinforced concrete (SFC) or self-stressing concrete (SSC) alone was used; however, an enhancement was achieved with the combination, i.e., steel fibre-reinforced self-stressing concrete (SFSSC). The results also indicated that SFC demonstrated a positive effect on ductility, whereas SSC decreased the deformation capacity. A finite element model was established for further analysis of retrofitted columns and comparison of the failure modes and load-shortening curves with the experimental results. The model was used to analyse the confinement of the concrete jacket and inner concrete. The curves of the load on the components indicated that the contribution of the concrete jacket to the peak load was lower than that of the outer tube owing to the uneven confinement effect, and the different types of concrete jackets only affected the load they bore. Based on the numerical database, equations for predicting the ultimate strengths of retrofitted columns with OC were proposed. A coefficient related to SSC was considered in the equations for predicting the capacities of columns with HPC. The calculated results showed good agreement between the experimental and numerical results.

本研究检验了用方钢管和混凝土护套加固的 26 根钢管混凝土方形短柱的性能，21 根钢管采用高性能混凝土 (HPC) 护套填充，5 根钢管填充普通混凝土 (OC)。破坏模式、载荷-轴向缩短曲线、延性指数和应变分析的测试结果表明，钢纤维混凝土（SFC）或自应力混凝土（SSC）对承载能力没有明显影响。单独使用；然而，通过组合实现了增强，即钢纤维增强自应力混凝土（SFSSC）。结果还表明 SFC 对延展性有积极影响，而 SSC 降低了变形能力。建立了有限元模型，以进一步分析改造后的柱子，并将破坏模式和荷载-缩短曲线与实验结果进行比较。该模型用于分析混凝土护套和内部混凝土的约束。各构件载荷曲线表明，由于不均匀的约束效应，混凝土护套对峰值载荷的贡献低于外管，不同类型的混凝土护套仅对其承受的载荷产生影响。以数值数据库为基础，提出了含OC的改造柱极限强度的预测方程。在用于预测具有 HPC 的色谱柱容量的方程中考虑了与 SSC 相关的系数。