Study Of The Bond Performance Between CFRP Strips And Concrete In NSM Reinforcement

As a very promising strengthening technique, NSM FRP technology has beenwidely arousing the attention of engineering field.As an innovation to the EBRtechnique to mitigate the risk of premature debonding failure, domestic and foreignscholars made considerable research characterizing the use of FRP as NSMreinforcement .The same as the EBR technique,the key problem is the bondperformance between FRP and concrete,however NSM FRP technology has moreinfluence factors on it ,also unlike EBR system，fewer design indications arecurrently available.This thesis conducted bond test focused on the influence factorsin the FRP-concrete interfacial bond performance , and established the theoreticalmodel analysis, aimed at fully exploiting the FRP superior properties.33 single shear tests were carried out on concrete prisms with NSM systems ,examined the influence facors including concrete strength ,groove size, grooveedge effect, the bond length and filling material, and analyzed the correspondingstrain data .The results of the study show that, with the increase of the concretestrength, specimens have a certain growth on bearing capacity, and found thathigher strength presented a certain inhibition to the debonding of the FRP-resininterface;Along with the increase of the groove width, the bearing capacity wasslowly increasing , specimen with wider groove effectively reduced the length ofthe debonding;The distance from groove edge to the prism edge beyond 40 mm andthe impact on bond performance can be ignored;Along with the growth of the bondlength, the resistance stress of FRP-concrete interface increases ,after debondingfailure the residual friction is also increasing,found there is a development lengthin the NSM FRP strips system;Compared to structure adhesive glue,Sika30 had asuperior properties.The theoretical analysis was using the trilinear model, and the bondmechanism of CFRP strips-concrete interface is divided into three stages, namelyelastic stage, softening and debonding stage, completely debonding stage.Theoryanalysis worked out the differential equation of the trips-concrete interfacial,through the mathematical deduction for each phase, slip distribution function, thebond shear stress distribution function,and axial stress distribution function withinthe scope of the bond length,and gained for the bearing capacity calculationformula.The results showes that the theoretical value has a good agreement with the experimental value.