方钢管螺旋筋复合约束混凝土柱偏压性能试验及承载力计算

为研究方钢管螺旋筋复合约束混凝土柱的偏心受压性能，完成了18个试件(其中17个方钢管螺旋筋复合约束混凝土试件和1个普通方钢管混凝土对比试件)的偏心受压加载试验。考虑了螺旋筋间距、径宽比、长细比、偏心率、纵筋配筋率以及钢管壁厚6个变化参数，通过试验，观察了试件的受力破坏过程及形态，获取了荷载 挠度曲线和荷载-应变曲线，分析了各变化参数对其偏压性能的影响规律。结果表明：方钢管螺旋筋复合约束混凝土的承载性能和破坏形态与普通方钢管混凝土的相似；螺旋筋主要在弹塑性和下降段发挥作用，并可提高试件的承载力和延性，延缓钢管壁的局部鼓曲，且材料强度能够充分发挥，其间距越密试件的变形性能越好；偏心率和钢管壁厚对承载力影响显著，其他参数的影响相对较小。最后提出了基于偏心率折减系数和内力相关关系的偏压承载力计算式，计算值与试验值均吻合较好。

Experimental investigation on mechanical performance and bearing capacity calculation of spiral stirrup-reinforced concrete-filled square steel tubular columns under eccentric compression

In order to investigate the mechanical performance of square steel tubular and spiral stirrup confined concrete columns under eccentric loading, eighteen specimens were prepared for eccentric loading test, including seventeen square steel tubular and spiral stirrup confined concrete columns and one conventional concrete-filled square steel tubular column. Six parameters were considered including the spacing of spiral stirrup, radius of spiral stirrup to side length of square steel tubular ratio, slenderness ratio, eccentricity ratio, longitudinal steel ratio and thickness of steel tube. The failure process and modes were observed and the load deformation and load strain curves were obtained, on the basis of which the influence of various parameters on the performance of specimens was discussed. The results show that square steel tubular and spiral stirrup confined concrete columns exhibit similar failure mode with conventional concrete-filled steel tubular columns. Spiral stirrups play an important role mainly in the elasto-plastic and descending stages, which can also improve the bearing capacity and ductility of the specimens, as well as delay the local buckling of steel tube. Meanwhile, the strengths of different materials can be fully utilized, and the deformation properties of the specimen decreases with the spacing of spiral stirrup. The eccentricity ratio and the thickness of steel tube have a significant effect on the bearing capacity, while the influence of other parameters is relatively small. Finally, two calculation formulas of the bearing capacity under eccentric loading were proposed, which both agreed well with the test results.