方钢管混凝土短柱的轴压承载力简化计算方法研究

Research on simplified calculation method of axial compressive bearing capacity of concrete-filled square steel tubular short column

为提高方钢管混凝土短柱轴压承载力的计算精度和效率,收集了国内外167个方钢管混凝土短柱的轴压试验资料;探讨了方钢管混凝土短柱在两种不同加载方式下的破坏机理,阐明了方钢管混凝土短柱轴压极限承载力不受加载方式影响的原因;引入“约束效应”系数,分析了混凝土强度、钢管强度、钢管宽厚比(B/t)对“约束效应”的影响;以极限平衡理论为基础,从方钢管混凝土短柱的理想轴压极限状态出发,推导了轴压承载力计算公式;考虑了方钢管对核心混凝土约束的不均匀问题,从而修正了方钢管混凝土短柱的轴压承载力计算公式。计算结果表明:该计算方法能够准确计算出方钢管混凝土短柱的轴压承载力。将该计算方法与中、美两国规范计算方法对比后发现,该方法计算结果比中国规范略微保守,较美国规范经济。该公式可以应用于B/t≥20的方钢管混凝土短柱轴压承载力计算。

To improve the calculation accuracy and efficiency of axial compressive bearing capacity of concrete-filled square steel tubular(CFST) short columns, the axial compressive test data of 167 specimens of CFST short columns were collected. The failure mechanism of CFST short columns was discussed under two different loading modes, and the reason was clarified why the axial compression ultimate bearing capacity of CFST short column was not affected by loading modes. The influence of concrete strength, steel tubular strength and steel tubular width thickness ratio(B/t) on restraint effect was analyzed by introducing restraint effect coefficient. Based on limit equilibrium theory, the formula for calculating the axial compressive bearing capacity was deduced from the ideal axial compression limit state of the CFST short column. The problem of confinement non-uniformity was considered with square steel tube to core concrete, and the formula for calculating the axial compressive bearing capacity of CFST short column was modified. The calculation results show that the method can accurately calculate the axial compressive bearing capacity of CFST short columns. Compared with the calculation method of Chinese and America standard, it was found that the calculation result of the method is more conservative than that of China and more economical than that of America. The formula could be used to calculate the axial compressive bearing capacity of CFST short columns of B/t≥20.