内置箍筋约束能显著提升钢管混凝土（CFST）柱的抗火性能，且在无任何防火保护的情况下，仍可使构件满足对应耐火等级的设计要求，为结构防火设计和延长结构安全服役寿命提供了新途径。该文设计制作了3根足尺矩形CFST柱，对其进行标准火灾与荷载耦合作用下的明火试验，探究内置矩形螺旋箍筋对该类构件抗火性能的提升效果，并考察箍筋间距对其抗火性能的影响规律。基于材料现有的高温力学本构关系，建立了火灾作用下矩形螺旋箍筋约束矩形CFST柱的数值分析模型，揭示高温环境下箍筋约束核心混凝土对该类构件耐火极限的提升机理。研究结果表明：在总用钢量相同甚至略低的情况下，内置矩形螺旋箍筋可显著改善矩形CFST柱的耐火性能，耐火极限提升幅度高达104.1%；通过合理设计箍筋参数，该类轴压柱无需在钢管表面设置防火保护层，即可满足150 min的二级耐火等级要求；箍筋间距从40 mm增至80 mm时，对该类构件耐火性能的影响较小；所建数值模型可较好地预测内置矩形螺旋箍筋约束矩形CFST柱的耐火极限，但对构件不同受火时间下的变形预测精度欠佳。

Internal stirrup confinement can significantly enhance the fire resistance of concrete-filled steel tubular (CFST) columns. Even without any fire protection, this approach still enables the columns to meet the design requirements for the corresponding fire resistance rating, providing a novel method for structural fire protection design and enhancing the safe service life of structures. This paper designed and fabricated three full-scale rectangular CFST columns and conducted fire test on them under the combined effects of standard fire exposure and axial loading. The study investigated the fire performance enhancement of such members via internal rectangular spiral stirrups, and examined the influence of stirrup spacing on their fire resistance. Based on the existing mechanical constitutive models of materials at elevated temperature, this study developed a numerical model for rectangular CFST columns and revealed the mechanism by which the spiral stirrups constrain the core concrete to enhance the fire resistance. The research results indicate that, with equivalent or slightly lower total steel usage, the internal rectangular spiral stirrups can significantly improve the fire resistance of such columns, with an increase in fire resistance of up to 104.1%. By reasonably designing the stirrups parameters, this type of axially compressed column can meet the Class Ⅱ fire resistance rating requirements for 150 minutes without the need of a fire protection layer on the steel tube surface. When the stirrup spacing increases from 40 mm to 80 mm, its effect on the fire resistance of such members is relatively small. The established numerical model can effectively predict the fire resistance of rectangular CFST columns with internal rectangular spiral stirrups, but its accuracy in predicting deformation at different heating time is less satisfactory.