This paper presents an extensive experimental investigation of the circular recycled aggregate concrete filled steel tubes (RACFST) stub columns under to axial compression to assess their cross-section behaviour. Recycled aggregate concrete is a sustainable concrete produced with recycled coarse aggregate (RAC) from demolition wastes generally used to fabricate non-structural elements. When compared with natural coarse aggregate (NCA), the recycled coarse aggregate presents lower mechanical properties due to physical and chemical changes that occurred during the recycling process, and thus the resulting RAC possess lower strength than the conventional natural aggregate concrete. However, the confinement provided by the circular steel tube can increase the strength and ductility of RAC in recycled aggregate concrete filled steel tubes (RACFST) columns. The test programme presented in this paper comprised twenty-three composite columns with replacement ratios (the mass percentages of the NCA replaced by RCA in concrete) corresponding to 0% (nature coarse aggregate), 30 and 50% (recycled aggregate concrete), plus four steel columns used for comparison. The experiments have shown that, as anticipated, the concrete core enhances the composite section load-carrying capacity. However, the control over the contents of this concrete core influences the composite section's ductility. If the fill material presents a brittle behaviour, stress redistributions occur in both steel and concrete to compensate for this effect. Since the behaviour of natural aggregate concrete filled steel tubes (NACFST) and RACFST columns are similar, the present paper starts from a study based on a comparative assessment of the recommendations presented in ABNT NBR 8800, ABNT NBR 16239, AISC 360–16, Eurocode 4 and Australian/New Zealand AS/NZS 2327 design standards. These design recommendations proved to be consistent and in line with the performed experiments. Additionally, the results indicated that the cross-section slenderness ratio (D/t) and the confinement ratio directly influence the composite section response.

本文对圆形再生骨料混凝土填充钢管 (RACFST) 短柱在轴压下进行了广泛的实验研究，以评估其横截面行为。再生骨料混凝土是一种可持续混凝土，由回收粗骨料 (RAC) 制成，这些粗骨料来自通常用于制造非结构元件的拆除废物。与天然粗骨料（NCA）相比，再生粗骨料由于再生过程中发生的物理和化学变化而表现出较低的力学性能，因此所得RAC的强度低于常规天然骨料混凝土。然而，圆形钢管提供的约束可以增加再生骨料混凝土填充钢管 (RACFST) 柱中 RAC 的强度和延展性。本文提出的测试程序包括 23 个复合柱，其替代率（NCA 在混凝土中被 RCA 替代的质量百分比）对应于 0%（天然粗骨料）、30% 和 50%（再生骨料混凝土），加上四个钢柱用于比较。实验表明，正如预期的那样，混凝土芯增强了复合截面的承载能力。然而，对该混凝土核心内容物的控制会影响复合截面的延展性。如果填充材料表现出脆性，钢和混凝土中都会发生应力重新分布以补偿这种影响。由于天然骨料混凝土填充钢管 (NACFST) 和 RACFST 柱的行为相似，因此本文从一项基于对 ABNT NBR 8800、ABNT NBR 16239、AISC 360–16、欧洲规范中提出的建议进行比较评估的研究开始4 和澳大利亚/新西兰 AS/NZS 2327 设计标准。这些设计建议被证明是一致的，并且符合所进行的实验。此外，结果表明，截面长细比 (D/t) 和约束比直接影响复合截面响应。欧洲规范 4 和澳大利亚/新西兰 AS/NZS 2327 设计标准。这些设计建议被证明是一致的，并且符合所进行的实验。此外，结果表明，截面长细比 (D/t) 和约束比直接影响复合截面响应。欧洲规范 4 和澳大利亚/新西兰 AS/NZS 2327 设计标准。这些设计建议被证明是一致的，并且符合所进行的实验。此外，结果表明，截面长细比 (D/t) 和约束比直接影响复合截面响应。