Study On The Mechanism Of FRP-Concrete Interfacial Debonding Under Impact

In practice,due to design errors,construction defects or environmental erosion and improper use during the service period,concrete structures are damaged or aged,leading to a series of issues,such as cracking,large deformation,lack of bearing capacity,which seriously affects the safety and reliability of the structure.Thus,structural reinforcement is required for further use.In recent years,fiber reinforced polymer(FRP)is widely used for structural reinforcement because of its lightweight,high strength,corrosion resistance and many other advantages.FRP and concrete collaborate by pasting FRP on the surface of concrete components,to improve the bearing capacity of structural components,reduce the structural deformation and limit the width of cracks.However,interfacial debonding is a common phenomenon due to low interfacial strength,and the strength of FRP cannot be fully used.Therefore,the research on the interfacial bonding performance and failure mechanism has become a hotspot in the field of FRP reinforced concrete structures.In this thesis,based on linear elastic theory,a bond-slip model of the interface between FRP and concrete is established in which the strain-rate-effect is considered.The interfacial bonding performance between FRP and concrete under quasi-static load and low speed impact load is studied in detail through single-face shear test and tension test.The experimental results are verified by the finite element simulation.The following four points are covered:(1)Based on the concrete dynamic constitutive model considering the strainrate-effect,proposed by Kulkarni and Shah,the theoretical model of FRP-concrete interfacial fracture energy,distribution of shear stress and interfacial bond-slip model is deduced.(2)Tensile bond failure tests were conducted to 55 FRP-concrete specimens,and the modes of tensile bond failure were obtained.The effects of parameters,such as the strength of concrete,type of FRP,type of binder and loading rate,on the interfacial bond strength between FRP and concrete were discussed.(3)The single-face shear tests were conducted to 75 FRP-concrete specimens,and the typical failure modes of shear debonding were obtained.The effects ofparameters,such as the strength of concrete,type of FRP,type of binder and loading rate,on the interfacial fracture energy,strain distribution of FRP,development of interfacial shear stress,effective bond length of FRP and interfacial bond-slip relationship,were discussed.Strain distribution of FRP,development of interfacial shear stress and interfacial bond-slip curves are fitted by using the theoretical model to verify the reliability of the bond-slip model.(4)Based on the commercial software ABAQUS,the FRP-concrete interface was simulated by cohesive element.The single-face shear tests were simulated under static and dynamic loads respectively.The numerical results,including strain distribution of FRP,distribution of interfacial shear stress,the bond-slip curves,are compared with the experimental results to verify the accuracy of the bond-slip model proposed in this thesis.