To research the flexural performance of ultra-high performance concrete (UHPC) filled high-strength steel tube (UHPCFST) and UHPC filled double skin high-strength steel tube (UHPCFDST) under bending load, an experimental investigation was presented. In this paper, four UHPCFST specimens, one UHPCFDST with square tube inner specimen and three UHPCFDST with circular tube inner specimens were designed to evaluate the influence of steel ratio, steel yield strength, and cross-section combination form on the flexural performance of the specimens. Experimental results indicated that the composite action between UHPC and high-strength steel tube was efficient, all specimens showed ductile failure under pure bending load. As the steel ratio and steel yield strength increased, the ultimate flexural capacity of specimens significantly increased, but the changes of flexural stiffness were not obvious. The results also demonstrated that when the hollow section ratio was 0.535 to 0.567, the UHPCFDST with circular tube inner specimens had higher ultimate flexural capacity and ductility than the UHPCFST specimens. Compared with square inner tube, when the steel ratio was the same, circular inner tube was recommended for UHPCFDST specimens. An analytical model of ultimate flexural capacity for UHPCFST and UHPCFDST specimens was proposed. Compared with the three current codes, the accuracy of the model was proved.

中文翻译：

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超高性能混凝土填充高强钢管抗弯性能

为研究超高性能混凝土（UHPC）填充高强度钢管（UHPCFST）和UHPC填充双皮高强度钢管（UHPCFDST）在弯曲载荷下的弯曲性能，进行了试验研究。本文设计了4个UHPCFST试件、1个方管内试件UHPCFDST和3个圆管内试件UHPCFDST，评价钢比、钢材屈服强度、截面组合形式对试件抗弯性能的影响。 . 实验结果表明，UHPC与高强钢管的复合作用是有效的，所有试件在纯弯曲载荷下均表现出延性破坏。随着钢比和钢屈服强度的增加，试件的极限抗弯承载力显着增加，但抗弯刚度变化不明显。结果还表明，当空心截面比为 0.535 至 0.567 时，带有圆管内试件的 UHPCFDST 具有比 UHPCFST 试件更高的极限抗弯能力和延展性。与方形内管相比，在钢比相同的情况下，UHPCFDST 试件推荐使用圆形内管。提出了UHPCFST和UHPCFDST试件的极限抗弯承载力分析模型。与现有的三个代码进行对比，证明了模型的准确性。与方形内管相比，在钢比相同的情况下，UHPCFDST 试件推荐使用圆形内管。提出了UHPCFST和UHPCFDST试件的极限抗弯承载力分析模型。与现有的三个代码进行对比，证明了模型的准确性。与方形内管相比，在钢比相同的情况下，UHPCFDST 试件推荐使用圆形内管。提出了UHPCFST和UHPCFDST试件的极限抗弯承载力分析模型。与现有的三个代码进行对比，证明了模型的准确性。