螺旋筋约束增强钢-混凝土组合方柱偏压性能及承载力计算

为研究复合约束效应对螺旋筋约束增强钢-混凝土组合方柱偏压性能的影响，设计并完成了30个螺旋筋约束增强钢-混凝土组合方柱(15个角钢试件、15个钢管试件)的偏心受压试验，观察了试件的破坏过程及模式，获取了荷载-跨中挠度曲线和荷载-应变曲线，对比分析了各变化参数对试件偏压性能指标的影响，并讨论了复合约束下2类组合柱的刚度退化规律。结果表明：组合柱偏压破坏模式分为大、小偏压破坏；内置螺旋筋可显著提升钢-混凝土柱的偏压承载力和变形性能，抗弯刚度也有所改善，但过密布置螺旋筋将导致组合柱的承载力和抗弯刚度提升程度下降；增大螺旋筋径宽比和角钢/钢管纵向配钢率能显著增大组合柱的承载力和抗弯刚度，但纵向配钢率对变形性能的影响远小于螺旋筋配箍率；螺旋筋间距减小及径宽比增大可减缓组合柱的刚度退化速率；此外，复合约束效应对角钢混凝土柱偏压性能的改善显著优于钢管混凝土柱；基于压溃理论推导的组合柱偏压承载力解析公式的计算结果与试验结果吻合较好。

ECCENTRIC COMPRESSION BEHAVIOR AND BEARING CAPACITY CALCULATION OF STEEL-CONCRETE COMPOSITE SQUARE COLUMNS CONFINED WITH SPIRAL BARS

In order to study the influence of composite restraint effect on eccentric compression behavior of steel-concrete composite square columns with spiral bars, 30 specimens of steel-concrete composite square columns confined with spiral bars, including 15 angle steel specimens and 15 steel tube specimens, were tested under eccentric compression. The failure process and pattern of the specimens were observed, the load-midspan deflection curve and load-strain curve were obtained, and the influence of various parameters on the eccentric compression behavior of the specimens was compared and analyzed. At last, the stiffness degradation law of the two types of composite columns under composite constraints was discussed. The results show that the failure patterns of composite columns are divided into large and small eccentric compression. Internal spiral bars can significantly improve the eccentric bearing capacity and deformation performance of steel-concrete columns, and can also improve the bending stiffness, but the improvement of bearing capacity and flexural stiffness of composite columns will be reduced if the spiral bars are arranged too closely. Moreover, the bearing capacity and bending stiffness of composite columns can be significantly increased by increasing the diameter width ratio of spiral bars and the longitudinal steel ratio of angle steel or steel tube, but the influence of longitudinal steel ratio on deformation performance is far less than that of spiral bars. The stiffness degradation rate of composite columns can be slowed down by decreasing the spacing of spiral bars and increasing the ratio of diameter to width. Additionally, the composite restraint effect on eccentric compression behavior of angle steel reinforced concrete columns is significantly greater than that of concrete-filled steel tubular columns. The calculated results of the analytical formula based on the collapse theory are in good agreement with the experimental results.