不同加载速率下CFRP约束再生骨料混凝土重复轴压应力-应变关系

Cyclic stress-strain relationship of CFRP-confined recycled aggregates concrete under different loading rates

为研究碳纤维增强树脂复合材料(CFRP)约束再生骨料混凝土(RAC)在重复轴向压缩作用下的力学性能,对72根CFRP约束RAC圆柱进行了不同加载速率下的单调及重复轴压试验,分析了加载速率、再生骨料(RA)替代率和CFRP层数对CFRP约束RAC的破坏模式、极限状态、重复应力-应变关系的影响。试验结果表明:CFRP约束对100wt%RA替代率混凝土极限状态的增强效果最为显著,但其增强效果随着加载速率的增大而减小。相比于3 mm/min的加载速率,2层CFRP约束100wt%RA替代率混凝土在18 mm/min的加载速率下,其极限强度增强比降低了16.2%,极限应变增强比降低了22.6%。此外,重复轴压荷载作用下,卸载刚度和再加载刚度均与RA替代率和加载速率呈负相关,但加载速率的提升会削弱RA替代率的影响。最后,通过对试验数据的回归分析,建立了考虑加载速率与RA替代率耦合作用的CFRP约束RAC重复轴压应力-应变模型,模型预测曲线与本文的试验曲线和现有文献收集的试验曲线匹配良好。

This study experimentally investigated the mechanical behavior of carbon fiber reinforced polymer(CFRP) confined recycled aggregate concrete(RAC) under cyclic loading.In total,72 CFRP-confined circular RAC specimens were tested under monotonic and cyclic axial compression,with a focus on the various loading rates and recycled aggregate(RA) replacement ratios.Test results indicate that the reinforcing effect of CFRP confinement on the ultimate condition of the concrete with 100wt%RA replacement ratio is most pronounced.However,this enhancement diminishes as the loading rate increases.In comparison to a loading rate of 3 mm/min,for two layers of CFRP-confined concrete with 100wt%RA replacement ratio,the enhancement ratio in ultimate strength is reduced by 16.2%,and the enhancement ratio in ultimate strain is reduced by 22.6% at a loading rate of 18 mm/min.Furthermore,under cyclic axial compression loading,both the unloading stiffness and reloading stiffness exhibit a negative correlation with the RA replacement ratio and loading rate.Nevertheless,the loading rate increase weakens the RA ratio's influence.Based on a regression analysis of the experimental data,a new cyclic stress-strain model for CFRP-confined recycled aggregate concrete incorporating the coupled effects of loading rate and RA replacement ratio is proposed.The proposed model exhibits excellent agreement with the experimental curves in this paper and the collected stress-strain curves from the opening literature.