Study On Bond Strength Of FRP Concrete Interface Based On Finite Fracture Mechanics

As a new type of building material,fiber reinforced composite has been widely concerned in the field of architectural engineering because of its high strength to weight ratio and stiffness to weight ratio,good durability and convenient construction.According to the failure mode of FRP reinforced structure,the interfacial debonding between FRP and reinforcement is a common failure mode,and the effect of FRP is closely related to the interfacial bond behavior.Therefore,in the study of FRP-concrete structure,the interfacial bonding property between FRP and coagulation has become an important research topic.In this paper,the various factors that affect the bond properties of FRP concrete interface are studied and compared by experiments,and analyzed through a new mechanical model,in order to achieve the goal of fully exploiting the superior performance of FRP without increasing the cost of materials and the difficulty of construction.24 single shear specimens with external FRP were designed,the bonding interface between CFRP plate and concrete is taken as the research object.The effects of concrete strength grade,bond length,thickness of plate,adhesive thickness and type on the bond performance were investigated,provides an experimental basis for the research and design of FRP reinforced concrete,the main research work is as follows:1)Using a set of independent research and development of a single shear test device,the ultimate load,the average bond stress and the failure mode of the specimen under different control parameters are studied.The common effect especially for the thickness and types of adhesive strength of concrete,the three distribution of interfacial strain of FRP-concrete interfacial stress transfer,the evolution law of interface slip and interfacial bond slip mechanism were conducted in-depth discussion and analysis.2)The preparation of experimental materials in this part of the breakthrough using the VARI process(vacuum assisted resin perfusion)to produce CFRP sheet,in the early stages of the production process to sum up the experience of some of the processes and processes to improve measures,regardless of appearance or mechanical properties of the CFRP sheet are fully in line with the requirements.3)A new failure criterion is introduced,which is based on the finite fracture mechanics framework to characterize the failure of quasi brittle materials,the finite distance assumption of crack propagation is assumed to be a structural parameter rather than a material parameter,The value is determined by the matching condition of energy and stress(strain).Based on this criterion in the finite fracture mechanics model of FRP-concrete interface is established,effective bond length are calculated by MATLAB to obtain the model test of finite length and interface theory of ultimate load value,the crack propagation,and the experimental value compared to verify the finite fracture mechanics model is effective for accurate prediction of FRP-concrete interface bond strength.