High-strength concrete-encased-steel filled CFRP (carbon fiber reinforced polymer) tube (HCSFC) takes advantages of high strength of concrete, steel and confinement of FRP, resulting in enhanced structural load carrying capacity and deformability. In this study, expansive high-strength concrete is filled between CFRP tube and sectional steel to study the mechanical properties of high-strength expansive concrete-encased-steel filled CFRP tube (HECSFC) under monotonic and cyclic axial compression. Twenty-four specimens were fabricated in this study. The variables included the number of CFRP layers (0, 1, 2 layers), cross-sectional shape (circular and square), self-stress level (with or without self-stress) and loading mode (monotonic and cyclic). Test results show that the peak load of HCSFC specimen is greater than their nominal load-carrying capacity, which indicates that CFRP plays a confinement role on the internal core concrete-encased-steel. As the number of layers increases, both the normalized peak load and the ultimate axial strain increase. For specimens under the same number of layers, cross sectional shape and loading mode, the ultimate axial strain and strain reduction factor of self-stressing specimens are higher than those of nonprestressed specimens. At the same time, it is found that the confinement efficiency of CFRP on circular specimen is higher than that of square specimen. Analytical results show that the modified existing stress-strain models of CFRP confined concrete predict well with the experimental results.

中文翻译：

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轴向单调循环载荷作用下高强度膨胀混凝土包钢碳纤维增强聚合物管

高强度混凝土包钢CFRP（碳纤维增强聚合物）管（HCSFC）利用混凝土、钢材的高强度和玻璃钢的约束，增强了结构的承载能力和变形能力。本研究在CFRP管与型钢之间填充高强膨胀混凝土，研究高强膨胀混凝土包钢CFRP管（HECSFC）在单调循环轴压下的力学性能。在这项研究中制作了 24 个样品。变量包括 CFRP 层数（0、1、2 层）、横截面形状（圆形和方形）、自应力水平（有或没有自应力）和加载模式（单调和循环）。试验结果表明，HCSFC 试件的峰值载荷大于其标称承载能力，说明 CFRP 对内芯钢筋混凝土起约束作用。随着层数的增加，归一化峰值载荷和极限轴向应变都增加。对于相同层数、截面形状和加载方式的试件，自应力试件的极限轴向应变和应变折减系数均高于非预应力试件。同时发现CFRP对圆形试件的约束效率高于方形试件。分析结果表明，改进后的CFRP约束混凝土现有应力-应变模型与试验结果预测良好。这表明 CFRP 对内部核心混凝土包钢起约束作用。随着层数的增加，归一化峰值载荷和极限轴向应变都增加。对于相同层数、截面形状和加载方式的试件，自应力试件的极限轴向应变和应变折减系数均高于非预应力试件。同时发现CFRP对圆形试件的约束效率高于方形试件。分析结果表明，改进后的CFRP约束混凝土现有应力-应变模型与试验结果预测良好。这表明 CFRP 对内部核心混凝土包钢起约束作用。随着层数的增加，归一化峰值载荷和极限轴向应变都增加。对于相同层数、截面形状和加载方式的试件，自应力试件的极限轴向应变和应变折减系数均高于非预应力试件。同时发现CFRP对圆形试件的约束效率高于方形试件。分析结果表明，改进后的CFRP约束混凝土现有应力-应变模型与试验结果预测良好。对于相同层数、截面形状和加载方式的试件，自应力试件的极限轴向应变和应变折减系数均高于非预应力试件。同时发现CFRP对圆形试件的约束效率高于方形试件。分析结果表明，改进后的CFRP约束混凝土现有应力-应变模型与试验结果预测良好。对于相同层数、截面形状和加载方式的试件，自应力试件的极限轴向应变和应变折减系数均高于非预应力试件。同时发现CFRP对圆形试件的约束效率高于方形试件。分析结果表明，改进后的CFRP约束混凝土现有应力-应变模型与试验结果预测良好。