Abstract The concrete-filled double-tube (CFDT) columns have been proposed in recent years. The existence of inner steel tube can not only increase the confinement on core concrete, but also increase its fire resistance and anticorrosion performance. This makes it have a great application prospect in the field of ocean structure engineering. In this paper, the axial compression performance of square CFDT short columns is comprehensively analyzed. The specimens studied consist of an external steel tube (square hollow section) and an inner steel tube (circular hollow section), in which concrete is completely filled. The fine finite element (FE) method is used to simulate the performance of this column. Two constitutive models of confined concrete for square CFDT core concrete are proposed. In order to ensure the correctness of the model, the verification analysis of the model is carried out based on the previous experimental results, and the whole process of axial compression performance of CFDT columns is analyzed in detail. The concrete strength ( f c ' ), width-thickness ratio (B/ t o ), diameter-thickness ratio (d/ t i ), diameter-width ratio (d/B) and yield strength ( f y ) of square CFDT columns are compared and analyzed. The performance of CFDT columns with the same steel content is also analyzed, it is of great significance to improve the application of CFDT columns in marine environment or high temperature environment. Finally, new formulas for calculating the ultimate bearing capacity of CFDT short columns under axial compression are proposed. The results show that the new formulas can predict the strength of CFDT short columns well.

中文翻译：

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方形双筒混凝土短柱轴压性能分析及承载力计算

摘要 近年来提出了双管混凝土（CFDT）柱。内钢管的存在，不仅可以增加对核心混凝土的约束，还可以提高其耐火防腐性能。这使其在海洋结构工程领域具有很大的应用前景。本文综合分析了方形CFDT短柱的轴压性能。所研究的试样由外部钢管（方形空心截面）和内部钢管（圆形空心截面）组成，其中混凝土完全填充。使用精细有限元 (FE) 方法来模拟该柱的性能。提出了两种用于方形CFDT核心混凝土的约束混凝土本构模型。为了保证模型的正确性，在前期试验结果的基础上对模型进行了验证分析，详细分析了CFDT柱轴压性能的全过程。比较了方形CFDT柱的混凝土强度（fc'）、宽厚比（B/to）、径厚比（d/ti）、径宽比（d/B）和屈服强度（fy）分析了。还分析了相同含钢量CFDT柱的性能，对于提高CFDT柱在海洋环境或高温环境中的应用具有重要意义。最后，提出了计算CFDT短柱轴向受压极限承载力的新公式。结果表明，新公式可以很好地预测CFDT短柱的强度。