FRP-混凝土界面粘结行为的参数影响研究

FRP-混凝土界面的粘结性能对FRP加固混凝土结构力学行为和破坏模式有着重要影响。本文对表征FRP-混凝土界面粘结性能的三个重要参数(界面初始刚度、最大剪应力、界面破坏能)开展研究,通过13个单剪试件的试验考察了混凝土强度、胶层厚度和粘结长度等因素对界面粘结行为的影响,根据试验结果拟合了界面破坏能、最大剪切应力与胶层剪切刚度、混凝土强度之间的函数关系。在试验研究基础上,构建了外贴FRP-混凝土界面粘结的有限元模型。通过有限元分析考察了界面破坏能等三个参数不变的前提下,不同的局部粘结滑移本构关系对界面粘结行为的影响;进而研究了其中一个参数变化时引起的界面粘结性能改变。研究结果表明:界面粘结承载力随着胶层厚度增加而逐渐提高;胶层厚度与界面破坏能成正比,与峰值剪应力成反比;当界面破坏能等三个参数保持不变时,局部粘结滑移本构关系对FRP-混凝土界面粘结性能的影响较小;三个参数中的一个增大时将延缓界面破坏的过程。

On the Influence of Parameters on Bonding Behavior of FRP-Concrete Interface

Bonding properties of FRP-concrete interface have an important impact on structural mechanics behavior and failure mode of FRP reinforced concrete. Study of three important parameters (the interface initial stiffness, the maximum shear stress, and the interface fracture energy) which characterize FRP-concrete interface bonding properties was carried out. A total of 13 specimens were manufactured, and single shear pulling tests were conducted to investigate the influence of concrete strength, adhesive layer thickness and bond length on the interfacial bonding behavior. Based on experimental results, functions relating the interface fracture energy, the maximum shear stress with the shear stiffness of adhesive layer and the concrete strength were fitted. Based on experimental study, a finite element model was established for externally bonded FRP-concrete bonding interface. Through FE analysis, the influence of different local bond-slip constitutive relation on bond performance was studied, when above-mentioned three parameters remain constant. Furthermore, the variation of interface bonding property induced by only one of the above parameter was also studied. Results show that the bond capacity increases gradually with the adhesive thickness increase; adhesive layer thickness is proportional to interface fracture energy and is inversely proportional to the shear stress peak. There is no significant influence of bond-slip constitutive relationship on interface bonding behavior, when above-mentioned three parameters keep unchanged. The increase of one of above three parameters will delay interface failure process.