早龄期钢管混凝土短柱轴压性能试验与理论分析

为研究早龄期钢管混凝土的轴压性能,对同批次浇筑的钢管混凝土短柱进行不同混凝土龄期下的轴压试验研究,得到不同混凝土龄期下试件荷载-变形曲线和破坏形态.分析了不同龄期下试件的破坏形态、荷载-应变曲线以及极限承载力随龄期的变化规律;在已有混凝土龄期应力-应变关系基础上,将国标GB 50010中成熟期混凝土的本构关系扩展到可以适用早龄期混凝土的情况.结合上述试验建立了早龄期钢管混凝土短柱的轴压有限元模型,并对早龄期圆形和方形钢管混凝土的轴压性能进行分析,结果表明:早龄期钢管混凝土的套箍效应随着龄期的增长而增大,且圆形截面的套箍作用和受力性能明显高于方形截面;在成熟期钢管混凝土短柱轴压承载力计算公式的基础上,通过引入龄期套箍修正系数建立了早龄期钢管混凝土短柱的强度承载力计算公式,并采用均匀设计方法对不同龄期圆形和方形钢管混凝土短柱的轴压承载力进行了模拟,从而验证了公式的适用性,而且具有较高的准确性.该研究将为钢管混凝土结构的安全施工提供参考.

Experimental and theoretical analysis on axial compression behavior of concrete-filled steel tube stub columns at early-age

To study the axial compression behavior of concrete-filled steel tube (CFST) at early-age, axial compressive tests of CFST stub columns at different concrete ages were carried out. The bearing capacity and load-strain curve at different ages were obtained. The failure modes, load-strain curves, and the development rules of bearing capacity with age were analyzed. Based on the existing stress-strain relationship of early-age concrete, the constitutive relationship of mature concrete in the GB 50010 was extended to include the case of concrete at early-age. Combined with the above mentioned tests, the finite element model for early-age CFST was established and the axial compression behavior of circular and square CFST at early-age was analyzed. The results show that the confinement effect increases with the growth of age and the confinement effect and load properties of the circular section aresignificantly higher than those of the square section. Based on the bearing capacity of CFST in the mature period, the strength capacity of CFST stub columns at the early age was established by introducing the coefficient of confinement effect due to concrete age. Uniform design method was used to simulate the age-bearing capacity of circular and square CFST stub columns to verify the applicability and high accuracy of the formula. This study provides references for the safe construction of CFST.