方中空不锈钢管混凝土短柱轴压承载力性能

为促进方中空不锈钢管混凝土构件在土木工程中的应用,以不锈钢外管厚度和混凝土强度为变量的6组试件为研究对象,首先,进行轴压试验,得到了不同试件在轴压荷载作用下的破坏模式、荷载-位移曲线、荷载-应变曲线,并进一步分析了不锈钢方管宽厚比、核心混凝土强度以及不锈钢方管约束效应系数对方中空不锈钢管混凝土短柱极限承载力的影响;然后,初步讨论了倒角对强度和延性的影响,提出了避免内管先于外管屈曲的最小厚度计算方法;最后,基于试验结果以及已有文献数据,采用拟合方法推导了方中空不锈钢管混凝土短柱的抗压承载力计算式,并与已有文献的简化模型及国外主要规范的计算结果进行对比.研究结果表明：试件宽厚比由34.9降至20.9,极限承载力的提升率平均为98.5%,核心混凝土强度由C40提升至C60时,试件极限承载力的提升率平均为7.3%;短柱的轴压极限承载力随约束效应系数近似呈线性增加,约束效应系数ξ越大,短柱的承载力越高;本文得到的计算式可以较好地预测方中空不锈钢管混凝土短柱的轴压承载力.

Bearing Capacity of Concrete-Filled Double Skin Stub Columns with Square outer Stainless Steel tube Under Axial Compression

In order to promote the application of square concrete-filled double skin tube (SCFDST) columns with outer stainless steel tube in civil engineering, six groups of specimens with different outer tube thicknesses and different core concrete strength were tested under axial compression, and the failure modes, load–displacement curves, and load–strain curves were obtained. The influences of the width-to-thickness ratio of the stainless steel square tube, the strength of core concrete, and the restraint effect coefficient of stainless steel square tube on the ultimate bearing capacity of SCFDST short columns were further analyzed. Meanwhile, the influence of chamfer on the strength and ductility of specimens was discussed preliminarily, and the minimum thickness calculation method to avoid the inner tube buckling before the outer tube buckling was proposed. Finally, based on the test results and the data in the existing literature, a fitted formula for calculating the compressive capacity of SCFDST short columns was derived; the calculated results by the proposed method were compared with those by the simplified model in the literature and the main foreign specifications, to verify its effectiveness. The results show that with the width-to-thickness ratio decreasing from 34.9 to 20.9, the ultimate bearing capacity was increased by 98.5% on average. When the core concrete strength was increased from C40 to C60, the ultimate bearing capacity of the specimen was increased by 7.3% on average. Besides, the axial ultimate bearing capacity of SCFDST short columns increases linearly with the constraint effect coefficient. Compared with the simplified model in the literature, the formula obtained in this study can predict the bearing capacity of SCFDST short columns.