BFRP约束损伤混凝土圆柱体长细比效应

Slenderness ratio effect of BFRP-confined damaged concrete cylinders

为研究长细比效应对BFRP(玄武岩纤维增强复合材料)约束完好及损伤混凝土轴压力学性能的影响规律,首先对3组不同长细比的素混凝土圆柱体试件进行轴压预加载,考虑了3种不同程度初始损伤,随后采用3种BFRP层数包裹加固并再次进行轴压试验。结果表明,损伤混凝土经BFRP约束后其抗压强度和变形能力仍能得到有效改善,但损伤等级对BFRP约束混凝土的强度、初始弹性模量等力学性能具明显不利的影响。通过直观分析与多因素析因分析,发现BFRP约束完好及损伤混凝土的极限强度具有长细比效应,随着长细比的增加,极限强度逐渐下降,而极限应变则无明显规律。值得注意的是,随着约束层数的增多,长细比效应对强度的影响可能有所下降,而随着损伤等级的加重,长细比效应对强度的影响反而可能会增加。考虑约束层数与损伤等级对长细比的交互效应,建立了考虑长细比效应的极限强度模型,模型预测结果与试验结果吻合良好。

To investigate the slenderness ratio effect on the axial compression mechanical behavior of BFRP-confined undamaged concrete and damaged concrete, three groups of plain concrete cylinders with different slenderness ratios were pre-loaded under axial compression loading. Three damaged levels were considered. The damaged concrete cylinders were wrapped with three kinds of BFRP layers and subjected to axial compression loading again. The test results show that the compression strength and deformation capacities of the damaged concrete can be effectively improved after BFRP confinement. However, the damaged levels had a noticeable adverse effect on the mechanical properties of BFRP-confined concrete(e.g. strength and initial elastic modulus). Through intuitive analysis and multifactorial analysis, it is found that the ultimate strength of BFRP-confined concrete had slenderness ratio effect. With the increase of slenderness ratio, the ultimate strength decreased, while the ultimate strain had no obvious trend. It should be noted that the effect of slenderness ratio on strength may decrease with the increase of confinement layers, while increase with the increase of damaged levels. An ultimate strength model was proposed for BFRP-confined damaged concrete with considering the interaction effect between the confinement layers and damaged levels on slenderness ratio. The proposed model showed a good agreement with the experimental results.