Formed carbon reinforcement - Influences on the load-bearing behavior

In this paper, the bond behavior and load-bearing capacity of formedcarbon fiber reinforced polymer (CFRP) reinforcement in concrete is investigated,focusing on the influence of bending diameter and pre-anchorage length onstructural performance. A three-zone model was developed to describe the bondof formed reinforcement and critical knowledge gaps regarding the mechanicalbehavior of geometrically formed CFRP reinforcement were addressed.Methods: A mathematical three-zone model was developed that divides thebond of formed reinforcement into pre-anchorage, formed region, and postanchoragesections. Systematic yarn pull-out tests (YPO) were conducted onCFRP textile reinforcement with bending diameters ranging from 0 to 50mm ata constant deformation angle of 90. Two test series examined the effects of bendingdiameter (with 10mm pre-anchorage) and pre-anchorage length variation (0and 10mm) at 30mm bending diameter.Results: The results indicate that decreasing bending radius significantlyreduces load-bearing capacity due to increased transverse loading of anisotropiccarbon fibers. Pre-anchorage length appears to be a critical parameter, with specimenshaving 10mm pre-anchorage achieving approximately 2500N compared to1300N for specimens without pre-anchorage at 30mm bending diameter. Theexperimental findings suggest complex interactions between the three bond zonesthat extend beyond simple additive consideration.Conclusion: Based on the results, it is assumed that the different sections of thebond zone mutually influence each other, which necessitates revision of the developedthree-zone model. The identified parameters enable derivation of reduction factors for design of formed reinforcement areas and provide fundamental understandingfor safe and economical dimensioning of concrete structures with CFRPform reinforcement.