GFRP植筋与混凝土界面粘结性能试验研究

Experimental Study on Interfacial Bond Behavior Between Embedded Through-Section GFRP Bars and Concrete

摘要:

基于纤维增强复合材料(FRP)植筋(ETS)加固技术,考虑3种混凝土强度等级(C30、C40和C50)和3种玻璃纤维增强复合材料(GFRP)筋直径(8、12和16 mm),制作了18个拉拔试件,采用中心拉拔试验研究筋材直径与混凝土强度等级对GFRP植筋与混凝土界面粘结性能的影响。结果表明,筋材直径与混凝土强度对界面粘结破坏形态、荷载-滑移曲线和界面粘结强度均具有显著影响。当界面脱粘时,粘结-滑移关系曲线呈现完整的上升、下降和平稳3个阶段;若发生混凝土劈裂破坏或GFRP筋断裂,粘结-滑移关系曲线仅有上升段。当混凝土强度等级从C30增加到C50时,GFRP筋直径为8 mm和16 mm的试件粘结强度分别提高了37.35%和13.23%,但当筋材直径为12 mm时,随着混凝土强度的增加,试件的破坏模式由GFRP筋断裂转变为混凝土劈裂,混凝土约束能力不足导致界面粘结强度显著降低。筋材直径由8 mm增加至16 mm时,粘结长度的增加导致界面粘结应力分布不均匀性增强,C30、C40和C50混凝土试件的粘结强度分别降低了40.76%、47.82%和51.16%。

Abstract:

Considering three concrete strength grades (C30, C40 and C50) and three GFRP bar dia-meters (8, 12 and 16 mm), 18 GFRP anchors with pre-drilled holes and concrete pull-out specimens were fabricated based on the Embedded Through-Section (ETS) strengthening technique for Fibre Reinforced Plastic (FRP). The central pull-out test was used to study the influence of bar diameter and concrete strength grade on the interface bonding performance of GFRP anchor rods and concrete. Compared with the traditional drilling anchor rod method, this method is easier to operate and avoids the local damage to the concrete caused by drilling. The results show that the bar diameter and concrete strength have significant effects on the bond failure mode, load-slip curve and bond strength. When the interface is debonded, the bond slip curve presents three stages: rising, falling and stable. In case of concrete splitting failure or FRP bar fracture, the bond-slip curve has only an ascending segment. As the concrete strength grade increased from C30 to C50, the bond strength of specimens with diameters of 8 mm and 16 mm is increased by 37.35% and 13.23%, respectively. However, when the bar diameter is 12 mm, with the increase of concrete strength, the failure mode of the specimen changes from GFRP bar fracture to concrete splitting, and the lack of the concrete confinement leads to a significant decrease in the bond strength. With the increase of bar diameter from 8 mm to 16 mm, the increase of bond length leads to the enhancement of the non-uniform distribution of interfacial bond stresses, and the bond strength of C30, C40 and C50 concrete specimens decreases by 40.76%, 47.82% and 51.16%, respectively.