冻融循环与持续荷载共同作用下FRP片材-混凝土界面黏结性能的退化行为

为研究冻融循环影响下纤维增强复合材料(FRP)外贴加固混凝土结构的界面性能,通过双面剪切试验研究冻融循环与持续荷载共同作用下FRP片材-混凝土界面黏结性能的退化行为。在经历最大200次冻融循环作用后,对试件进行静态加载,并采用数字图像相关法量测试件表面的全场位移,进而计算界面黏结滑移关系。试验结果表明:冻融循环作用对FRP片材-混凝土界面的极限承载力、极限滑移、FRP最大应变、最大剪应力、界面断裂能等均有明显的削弱作用,界面黏结滑移曲线退化显著;预加荷载的存在加剧了冻融循环作用后界面黏结性能的退化;冻融循环作用前后界面的破坏模式也发生了显著改变。

Bond performance degradation behavior of FRP laminate-to-concrete interface under combined effects of freeze-thaw cycling and sustained loading

To study interfacial behavior of concrete structures strengthened with fiber reinforced polymer(FRP)subjected to the freeze-thaw cycling, this study presents experimental investigations on the degradation behavior of FRP laminate-to-concrete interfacial bond performance under combined effects of freeze-thaw cycling and sustained loading with double-lap shear tests. After being exposed up to 200 freeze-thaw cycles, the specimens were tested to failure monotonously. Digital image correlation method was employed to capture the full-field displacement of the specimen during loading. Interfacial bond stress-slip relationship was determined based on the analysis of full-field data. Test parameters included the freeze-thaw cycles, sustained loading and concrete types. Test results show that the freeze-thaw cycling leads to significant decreases in all interfacial parameters. The bond stress-slip relationship is also degenerated with freeze-thaw cycles seriously. When considering the sustained loading, additional interfacial degradations were observed after freeze-thaw cycling. Apparent changes of interfacial failure modes were also observed during tests.