Concrete-encased concrete-filled steel tubes (CFST) has extensive applications in the world. According to previous researches, if the CFST is placed in the compression zone, the confinement increases, and the compressive capacity of the concrete is completely used. The prestressed strands also increase the core concrete confinement and eliminate tension cracks. Therefore, in this paper, to achieve the benefits of CFST and prestressed strand, for the first time, a novel concept called prestressed concrete-encased CFST (PCE-CFST) beams were introduced. The main objective of the combination of steel tube and pre-stressed strands is to increase the core concrete compressive strength and control the concrete crack in the tension zone. Six beams were constructed using self-compacting concrete to investigate the influence of variations in the pre-stressing force level of the pre-stressed strands, the pre-stressed strands eccentricity, and the steel tubes diameter-to-thickness ratio on the structural performance of these members. The specimens were tested under four-point loading. The results showed that the pre-stressed strands increased the confinement effect on the core concrete and improved the bearing capacity, ductility, and bending stiffness. The steel tubes improved the bearing capacity, ductility, and energy absorption, while they did not significantly affect the bending stiffness. Finally, it was shown that the pre-stressed strands increased the bearing capacity, energy absorption, and bending stiffness in reinforced concrete beams.

中文翻译：

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预应力自密实钢管混凝土梁的结构性能

混凝土包裹的钢管混凝土（CFST）在世界范围内有着广泛的应用。根据以往的研究，如果将CFST置于受压区，则约束增加，混凝土的抗压能力得到充分利用。预应力钢绞线还增加了核心混凝土的约束并消除了张力裂缝。因此，在本文中，为了实现 CFST 和预应力钢绞线的优势，首次引入了一种称为预应力混凝土包裹 CFST (PCE-CFST) 梁的新概念。钢管与预应力钢绞线组合的主要目的是提高核心混凝土抗压强度，控制受拉区混凝土裂缝。使用自密实混凝土建造六根梁，研究预应力钢绞线的预应力水平、预应力钢绞线偏心距和钢管径厚比变化对结构性能的影响这些成员中。试样在四点加载下进行测试。结果表明，预应力钢绞线增加了对核心混凝土的约束作用，提高了承载力、延性和弯曲刚度。钢管提高了承载能力、延展性和能量吸收，而它们对弯曲刚度没有显着影响。最后，结果表明，预应力钢绞线增加了钢筋混凝土梁的承载能力、能量吸收和弯曲刚度。