The rectangular concrete‐filled steel tube (RCFST) has been widely applied into many engineering fields like buildings and bridges. However, the shear mechanisms and the universal design methods under lateral shear forces still remain to be fully understood. In this paper, the composite action of RCFST columns under lateral shear forces was systematically investigated with improved 3‐dimensional finite element simulations. The models adopted the improved material constitutive models and detailed contact interactions between the encased steel tube and core concrete. On the basis of available test data and numerical results of parametric studies, the critical shear span ratio and its variation range were determined. The composite effect and interactions between the encased steel tube and core concrete under different configurational dimensions and loading conditions were investigated. Calculation formulas of the shear stiffness and capacity were proposed based on identified features. The cooperative working mechanism and the constraining effect of steel tube were considered. The proposed calculations were then compared to available design regulations in different countries, and yielded more accurate predictions than the others.

中文翻译：

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矩形钢管混凝土柱在侧向剪力作用下的复合作用

矩形混凝土钢管（RCFST）已广泛应用于建筑和桥梁等许多工程领域。但是，在横向剪切力作用下的剪切机理和通用设计方法仍有待充分理解。本文利用改进的三维有限元模拟系统研究了RCFST柱在侧向剪力作用下的复合作用。这些模型采用了改进的材料本构模型，并采用了封闭钢管与芯混凝土之间的详细接触相互作用。根据可用的测试数据和参数研究的数值结果，确定了临界剪切跨度比及其变化范围。研究了在不同结构尺寸和载荷条件下，钢管与芯混凝土之间的复合作用和相互作用。根据确定的特征，提出了剪切刚度和承载力的计算公式。考虑了钢管的协同工作机理和约束效果。然后将提议的计算与不同国家/地区的可用设计法规进行比较，并得出比其他国家更准确的预测。