负载下碳纤维布约束混凝土方柱轴压应力-应变关系的试验研究与分析

Test and analysis of the axial stress-strain relationship of square-section concrete columns confined by CFRP under preload

通过16个碳纤维布约束混凝土方柱的轴压试验,研究了方柱在不同的负载水平和碳纤维包裹层数下的破坏特征和力学性能,并对负载导致约束混凝土峰值点应力和应变下降的原因进行了分析。试验结果表明,负载水平的大小对于碳纤维布的约束效果是有明显影响的。随着负载水平的提高,第二阶段刚度、峰值点应力和应变均逐渐下降;而碳纤维包裹层数的增加,则放大了这种效应。本文在已有未负荷状态下碳纤维布约束混凝土的相关研究成果的基础上,根据本文的试验结果,首次提出了考虑负载影响的第二阶段刚度、峰值点应力和应变的计算公式,并提出了考虑负载影响的碳纤维布约束混凝土方柱的应力-应变关系计算模型。

A total of 16 square-section concrete columns confined by CFRP sheet were tested under uniaxial compression with different preload ratios and CFRP plies. The failure characteristics and mechanical behavior of confined concrete columns were presented, and the decreases of the peak stress and strain of the confined concrete due to preload were analyzed. The experimental results indicated that the confinement effect of CFRP was evidently influenced by preload ratio. The second stiffness, the peak stress and strain declined with increasing preload ratio and the extent enhanced with increasing number of CFRP plies. Based on existing study of unconfined concrete and test data, the formulas of the second stiffness, the peak stress and strain of confined concrete with preload are determined, and a model for calculating the axial stress-strain curve of square-section concrete columns confined by CFRP under preload was presented.