圆钢管约束超高性能混凝土短柱轴压受力性能研究

为研究钢管约束超高性能混凝土（UHPC）短柱的套箍效应和轴压承载力，进行了12根钢管约束超高性能混凝土短柱的轴压试验，分析其破坏模式、变形及受力全过程。试验结果表明：钢管约束超高性能混凝土轴压短柱破坏模式与套箍系数相关，随着套箍系数的增大，轴压短柱分别出现剪切破坏、混合破坏和腰鼓破坏；套箍系数较小（0.43~0.52）的短柱，其破坏全过程中弹塑性段较短，表现出较明显的脆性破坏，当套箍系数较大（1.21~1.80）时，短柱破坏时的塑性明显增强。基于试验验证的有限元模型，参数分析表明，钢管套箍效应产生的承载力提高系数介于1.2~1.4之间；在0.43≤ξ≤1.08范围内，承载力提高系数随套箍系数增大而增大，建议径厚比的取值范围为12.0~23.0。通过对现有钢管约束混凝土承载力计算方法分析，提出了钢管约束超高性能混凝土轴压短柱承载力计算方法，其计算结果与试验结果吻合良好。

Mechanical behavior of circular steel tube confined ultra high performance concrete stub columns under axial compressive loading

To investigate the confined effect and axial compression strength of circular steel tube confined ultra high performance concrete (UHPC) stub columns, axial compression tests on 12 circular steel tube confined UHPC stub specimens were carried out, and the failure mode, deformation, and force transfer were analyzed. The test results show that the failure mode of circular steel tube confined UHPC stub specimens is related to the confinement factor. With the increase of confinement factor, the specimens show shear failure, mixed failure, and waist drum failure in order. The specimen with a smaller confinement factor (ranging from 0.43 to 0.52) has a shorter elastic-plastic stage in the whole failure process, showing a more obvious brittle failure, while the confinement factor of the specimen is large (ranging from 1.21 to 1.80), the plastic damage phenomenon would be enhanced. Based on the finite element model validated by experiments, parametric analysis was carried out, which shows that the ultimate capacity improvement coefficient varies from 1.2 to 1.4. In the range of 0.43≤ξ≤1.08, the ultimate capacity improvement coefficient increases with the increase of confinement factor, and the recommended value range of diameter-to-thickness ratio is 12.0-23.0. By comparing with the existing ultimate capacity formula, the predicting formula for the steel tube confined UHPC ultimate capacity was modified and its calculation results fit well with the experimental results.