CFRP配筋超高性能混凝土柱受压性能试验

Compression Behavior of Ultra-high-performance Concrete Columns Reinforced with Carbon-fiber-reinforced Polymer Bars

为明确碳纤维增强复合材料CFRP (Carbon Fiber-reinforced Polymer)配筋超高性能混凝土UHPC (Ultra-high-performance Concrete)柱的受力性能,对不同偏心率(e;/h;=0,0.15,0.3和0.6)下4根CFRP配筋UHPC柱试件进行受压性能试验研究,获得偏心率对其受压性能的影响规律,并提出CFRP配筋UHPC柱偏心距增大系数及承载能力计算公式。结果表明:所试验CFRP配筋UHPC柱的破坏形态均为受压破坏,UHPC压碎后会伴随受压区CFRP筋的折断而表现出脆性破坏特征;随着偏心率的增大,柱的承载能力逐渐减小,侧向变形及构件延性逐渐增大。CFRP筋较低的弹性模量和UHPC较大的极限压应变,使得柱的偏心距增大系数因二阶效应更趋明显而增大;截面受拉区UHPC的抗拉作用亦相应降低;预测受压破坏CFRP配筋UHPC柱的承载能力时,当偏心率不大于0.3时,可忽略受拉区UHPC的贡献;当偏心率大于0.3时,宜考虑截面受拉区UHPC的抗拉作用以反映UHPC较高抗拉强度的有利作用,此时受拉区UHPC的等效应力折减系数k建议取0.2。试验结果验证了所提柱偏心距增大系数及承载能力计算公式的适用性。

Four carbon-fiber-reinforced polymer(CFRP)-reinforced ultra-high-performance concrete(UHPC) columns with different eccentricities(e;/h;=0, 0.15, 0.3, and 0.6) were tested to investigate the behavior of UHPC columns reinforced with CFRP bars. The effects of the eccentricities on the behavior of the UHPC columns were analyzed, and calculation formulas of the eccentricity magnifying coefficient and bearing capacity of CFRP-reinforced UHPC columns were devised. The results show that the failure mode of the tested CFRP-reinforced UHPC columns is the crushing failure of the UHPC in the compression zone. The columns generally have brittle failure characteristics with the fracture of the CFRP bars in the compression zone after UHPC crushing. With the increase in eccentricity, the bearing capacity of the columns decreased gradually and the lateral deflection and member ductility increased gradually. The lower elastic modulus of the CFRP bars and the larger ultimate compressive strain of UHPC makes the eccentricity magnifying coefficient of the columns more evident owing to the second-order effect;moreover, the tensile effect of UHPC in the tensile zone of the section decreases correspondingly. When the bearing capacity of CFRP-reinforced UHPC columns with compression failure is predicted, if the eccentricity is not greater than 0.3, the contribution of UHPC in the tensile zone can be ignored. When the eccentricity exceeds 0.3, the tensile effect of UHPC in the tensile zone of the section should be considered to reflect the favorable effect of the higher tensile strength of the UHPC. At this time, the equivalent stress reduction coefficient k of UHPC in the tensile zone is recommended to be 0.2. The test results verify the applicability of the proposed formulas for calculating the eccentricity magnifying coefficient and bearing capacity of the CFRP-reinforced UHPC columns.