Study On The Influence Of Layer Thickness On The Interfacial Properties Of CFRP-concrete

In recent years,with the development of the national economy,people's requirements on the service conditions of buildings have been further improved.Some existing buildings can no longer meet the safety requirements and must be reinforced.At present,the commonly used methods for reinforcing concrete structures are steel encased method,enlarged section method,prestressed reinforcement method,additional fulcrum strengthening method and fiber reinforced composite(FRP)reinforcement method.With the maturity of CFRP production technology,CFRP reinforcement method is widely used.The bonding properties of CFRPconcrete interface plays an important role in the effect of CFRP reinforced concrete.At present,the research on the bonding properties of CFRP-concrete interface needs to be further strengthened.So,the influence of the adhesive layer thickness on the bonding performance of CFRP-concrete interface was studied in the paper,and force calculation model and interface constitutive model were modified.The specific research contents were listed as follows:(1)Single Shear Test: In the paper,32 single-shear test specimens were used to investigate the interaction influences on CFRP-concrete interfacial adhesion between adhesive layer thickness and bonding length,concrete strength,CFRP plate width and thickness separately.(2)Model Fitting: Based on the existing researches,the ultimate bearing capacity and interface constitutive model considering the adhesive layer thickness were proposed combined with the experimental data in the paper.(3)Finite element simulation: The finite element simulation of the ultimate bearing capacity and strain distribution of the specimen is carried out by introducing a special interface element between the CFRP plate element and the concrete element,and the results are compared with the experimental results.It is shown that the ultimate bearing capacity of the interface is increased with the thickness of the adhesive layer increasing.However,when the thickness of the CFRP plate researches to a certain value,the thickness of the adhesive layer has little effect on the ultimate bearing capacity of the interface.The ultimate bearing capacity of the interface increases with the thickness of CFRP plate increasing.With different layer thicknesses,the change of the CFRP plate thickness has different effects on the ultimate bearing capacity of specimens.In the width direction of the CFRP plate,there is a stress transition zone in the edge area where the CFRP plate is adhered to the concrete.In this transitional zone,the interfacial bonding stress is less than its central region.The width of this region is related to the thickness and elastic modulus of CFRP plate,the compressive strength of concrete,the thickness of adhesive layer and the property of concrete.With the concrete strength increasing,the ultimate bearing capacity of the interface is increased.With the concrete strength increasing,the failure mode of specimen is changed from the cracking of concrete to the destruction of plastic layer.It is shown that the modeling method can accurately simulate the structure performance of CFRP-concrete specimens.