嵌入式FRP与混凝土粘结界面基于塑性损伤理论的数值模拟及试验研究

The near-surface-mounted (NSM) FRP method is superior to externally bonded (EB) FRP method in terms of bonding performance, high FRP utilization efficiency, durability and fire-resistance, because the NSM FRP, which is embedded in concrete, usually has larger interfacial bonded area than its EB FRP counterpart. As a result, the past a few years have witnessed increasing interests both from engineers and researchers around the world. However, the bond strength and failure mechanism of the NSM FRP-concrete bonded interface needs further research due to the variation in failure mode and large number of affecting elements. Against the above background, this research project will investigate the bond behavior of the NSM FRP-concrete interface subject to monotonic loading. Different testing methods and accurate 3-D meso-scale FE model will be deployed to investigate the effects of various factors on the bond behavior. Based on experimental and numerical results, effects of a number of significant factors, including FRP section type and dimension, FRP material properties, FRP surface condition, bond length, the groove size and shape, the adhesive material properties and concrete strength, will be clarified. A bond-slip model capable of catering for different failure modes will be developed which will be used in the analyses and designs of RC structures strengthened with NSM FRP. The research project is of great research significance and application merit.

由于截面粘结面积大及FRP受混凝土包裹，嵌入式FRP与外贴式FRP相比具有较好的粘结性能、材料利用率、耐久性及防火性能，正逐渐受到工程技术人员与研究人员的重视。但由于嵌入式FRP与混凝土界面破坏模态，影响参数多，其粘结强度和破坏机理有待进一步研究。本项目将研究静荷载下嵌入式FRP -混凝土界面的粘结性能。采用嵌入式FRP-混凝土搭接接头单剪试验进行针对性试验研究，建立能考虑多种破坏模态的精细有限元模型并进行参数分析，澄清FRP截面形状、FRP表面情况、FRP材料性能、粘结长度、开槽尺寸、粘结剂性能和混凝土强度等对嵌入式FRP与混凝土界面粘结性能的影响，提出静载下FRP-混凝土界面粘结-滑移模型。预期成果将用于嵌入式FRP加固混凝土构件分析及指导实际加固设计，具有重要的科学性和工程应用价值。

由于嵌入式FRP与混凝土界面破坏模态，影响参数多，其粘结强度和破坏机理有待进一步研究。本项目通过单剪搭接头拉拔试验研究了静荷载下磷酸镁粘结剂嵌入式FRP -混凝土界面的粘结性能，发现硅灰和碳酸钙晶须能改善界面粘结性能，但受到掺量的限制，并采用SEM等微观技术对硅灰和碳酸钙晶须的作用机理进行分析。为澄清试件失效过程中，界面层应力、应变的变化情况，建立了能考虑多种破坏模态的3D精细有限元模型。其中，采用塑性损伤理论考虑混凝土非线性行为；采用界面粘结元模拟胶层破坏；采用Tie链接联结胶层与FRP层和混凝土层；采用动力数值分析方法进行计算分析。最后，基于建立的数据库，对既有粘结-滑移模型的不确定性系数进行了相关性分析，通过多元回归分析建立了不确定性系数函数模型，基于此对既有粘结-滑移模型进行修正，去除不确定性影响，提出具有统一可靠度的FRP-混凝土界面粘结-滑移模型。