Finite Element Analysis On Bonding Properties Of CFRP-concrete Interface

For several years,the CFRP-reinforced concrete technology has received extensive attention in the field of structural reinforcement with its good reinforcement effect.The bonding performance of CFRP-concrete interface directly determines the reinforcement effect,and the bonding performance of CFRP-concrete interface is affected by factors such as material itself and environment.In addition,the CFRP-reinforced concrete has a problem of premature peeling of the interface,which seriously affects the reinforcement effect.Therefore,it is of great significance to comprehensively study the bonding properties of CFRP-concrete interface under various conditions.Based on the existing experimental research,this paper conducts finite element analysis and research on the bonding performance of CFRP-concrete interface.The main research contents and results are as follows:(1)Finite element analysis of CFRP-concrete interface bonding performance.The double-sided shear test piece used in the test of this research group is the research object.Based on the cohesion model,the CFRP-concrete interface peeling failure process was accurately simulated.By analyzing the end load-slip curve obtained by finite element simulation,the interface peeling failure process can be divided into elastic stage,instability stage and stripping stage.Through the analysis of CFRP tensile stress,interface shear stress and concrete stress distribution at each development stage,the interface damage process is divided into four stages: the elastic stage,the softening-elastic stage,the peel-softening-elastic stage,and the peel-softening stage.And from the theoretical point of view,the theoretical analysis of the evolution of CFRP stress and interface shear stress in the above four stages is carried out,and the results can better reflect the peeling failure process of CFRP-concrete interface.(2)Study on the bonding properties of CFRP-concrete interface under environmental erosion.Through the further analysis and derivation of the test data of CFRP-concrete double-shear specimens in the sulfate attack environment of this research group,the relationship between CFRP-concrete interface parameters and sulfate corrosion time was studied.On this basis,the finite element analysis of CFRP-concrete interface with different corrosion time is carried out.Studies have shown that the sulfate corrosion makes the CFRP-concrete interface "soft",the effective bond length determined by the CFRP stress distribution curve increases with the corrosion time,Based on this,a prediction formula for effective bond length of CFRP-concrete interface considering sulfate corrosion is established.Based on the analysis of the interface ultimate bearing capacity of different corrosion time,the prediction formula of CFRP-concrete interface ultimate bearing capacity considering the sulfate attack was established,and the accuracy of the formula prediction was verified by comparison with the experimental results and finite element results.(3)The effect of applying pressure bar anchoring on the bond performance of CFRP-concrete interface.Considering the anisotropic properties of the fiber bead,the finite element study on the bond properties of CFRP-concrete anchored by the bead anchor is carried out.The results show that the load-slip curve of the CFRP-concrete interface end with anchoring can be divided into four stages: elastic stage,instability stage,stripping stage and anchoring strengthening stage.Through the stress analysis of CFRP brace and bead in each stage of loading,the stress transfer law and failure mechanism in the anchorage zone are studied.When the load approaches the initial peeling load,the anchoring bead begins to function,When the stress reaches the anchorage zone,a large stress concentration occurs on the bead on both sides of the bead and the thickness of the brace,which is also the starting position of the bead-concrete interface failure.Finally,the parameters of the anchorage length and width of the bead are analyzed.The results show that the change of anchorage length and width of the bead has a small increase in the initial peeling load of the interface;Under the same bead anchorage width(length),the ultimate bearing capacity of the interface increases with the anchorage length(width)of the bead.Compared with the anchorage length of the bead,the ultimate bearing capacity of the bead is more sensitive to the increase of the anchorage width of the bead;There is an optimum briquetting anchor length value related to the anchoring width of the bead.When the bead anchoring length is further increased,the ultimate bearing capacity is no longer increased.