大尺寸CFRP约束混凝土方柱的轴心抗压试验研究

试件的尺寸对于碳纤维增强塑料(CFRP)约束混凝土柱的性能具有重要影响,但目前在CFRP约束混凝土尺寸效应方面的研究基本上还处于空白.基于对7种不同倒角半径的大尺寸CFRP约束混凝土方柱的轴心抗压试验,获取了各组试件的破坏模式、抗压强度、应力-应变曲线、外包CFRP应变分布等基本力学性能,并与已有小尺寸试件的试验结果进行比较和分析.研究结果表明,试件的抗压强度随倒角半径比的增大而增大,外包CFRP对直角试件几乎无增强作用;所有试件的破坏都是由外包CFRP的拉断所导致,断裂位置均位于倒角范围内,应力集中的现象明显;约束效应比MCR可以较好地反映尺寸效应对抗压强度影响,试件尺寸的增大显著降低CFRP的约束效应;外包CFRP的极限应变低于其材性试验结果35%以上,明显大于对应的小试件试验结果;已有模型的计算结果与本试验的实测结果存在显著差异,故有必要考虑尺寸效应的影响.

Experimental Research on Large-scale Square Columns Confined with Wrapped CFRP under Axial Compressive Load

Although the size of specimens presents significant effect on the mechanical performance of CFRP confined concrete columns, the size effect is a blank area of study until now. Based on a series of tests on seven groups of Carbon Fibre Reinforced Plastics (CFRP) confined large-scale square concrete columns with different corner radius, the basic mechanical properties were obtained, such as the failure modes, compressive strengths, stress-strain relationships, and the ultimate strain distribution of CFRP jacket. Moreover, their comparison with the experimental results of the smaller-scale specimens has been investigated and published. It is demonstrated that the confined strength increases with the increase of the corner radius except for the specimens with sharp corner. All of the specimens fail due to CFRP rupture, and the fracture location occurs in the chamfer zone. Meanwhile, the phenomenon of the stress concentration is obvious. The confinement ratio, i.e., MCR, shows a certain correlation with the size of specimen on the compressive strength of CFRP confined specimens. The ultimate strains measured on the CFRP jackets are about 35% less than that tested by the coupon specimens, while it is more serious than that for the smaller-scale specimens. It is found that the discrepancies between the predicted results of the existing strength models of CFRP confined square column and the experimental results in this work are obvious. It suggests that the size effect on the FRP confined square columns cannot be ignored,which needs to be further researched.