This study presents an innovative composite column system featuring exceptional ductility and versatility, suitable for replacing traditional concrete columns or UHPC composite columns. The composite column, comprised of concrete-filled aligned steel fiber ultra-high performance concrete (UHPC) tubes (ASFUTs), offers superior mechanical properties. Apart from its function as a formwork, the ASFUT provides exceptional rigidity and lateral confinement capabilities, enabling it to withstand substantial axial forces directly. Initially, steel fibers were aligned using an electromagnetic field. Computed Tomography (CT) imaging elucidated an average inclination angle of 16.36° between the fibers and the circumference of ASFUT sections. Compared to conventional UHPC, aligned steel fiber UHPC demonstrates an average 9.1 % increase in compressive strength and an average 129.67 % increase in maximum equivalent tensile. This enhancement can be attributed to the improved fiber bridging effect resulting from the orientation of fibers. Then, the mechanical properties of the concrete-filled ASFUT columns were evaluated by axial compression testing of eight specimens with different fiber contents, shapes, and orientations. The findings indicate that the ASFUTs outperform conventional concrete-filled UHPC tubes, exhibiting notable enhancements across various performance metrics. Specifically, at a fiber volume fraction of 1 %, the concrete-filled ASFUT exhibits a compressive strength, elastic modulus, ductility, and energy dissipation capacity that are 1.12 times, 1.03 times, 1.25 times, and 1.54 times respectively, in comparison to conventional concrete-filled UHPC tubes. Finally, an advanced predictive model for estimating the axial bearing capacity of ASFUT concrete columns was proposed, offering valuable insights for structural design optimization and widespread implementation.

中文翻译：

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预制定向钢纤维UHPC混凝土管轴压性能

这项研究提出了一种创新的复合柱系统，具有卓越的延展性和多功能性，适合取代传统混凝土柱或 UHPC 复合柱。该复合柱由填充混凝土的对齐钢纤维超高性能混凝土 (UHPC) 管 (ASFUT) 组成，具有卓越的机械性能。除了作为模板的功能外，ASFUT 还提供卓越的刚性和横向限制能力，使其能够直接承受巨大的轴向力。最初，钢纤维使用电磁场排列。计算机断层扫描 (CT) 成像显示纤维与 ASFUT 切片圆周之间的平均倾斜角为 16.36°。与传统UHPC相比，定向钢纤维UHPC的抗压强度平均提高9.1%，最大等效拉伸强度平均提高129.67%。这种增强可归因于纤维取向所产生的纤维桥接效应的改善。然后，通过对八个不同纤维含量、形状和方向的试件进行轴压试验来评估 ASFUT 混凝土柱的力学性能。研究结果表明，ASFUT 的性能优于传统的混凝土填充 UHPC 管，在各种性能指标上都表现出显着的增强。具体而言，在纤维体积分数为1%时，混凝土填充ASFUT的抗压强度、弹性模量、延性和耗能能力分别是传统混凝土的1.12倍、1.03倍、1.25倍和1.54倍。混凝土填充 UHPC 管。最后，提出了一种用于估计 ASFUT 混凝土柱轴向承载力的先进预测模型，为结构设计优化和广泛实施提供了宝贵的见解。