Cohesive Zone Modelling of a Prestressed Non-Mechanical CFRP Anchorage Subjected to Freeze-Thaw Cycles

The application of prestressed carbon fiber reinforced polymers (CFRP) as an externally bonded reinforcement has attracted significant attention due to its well-known advantages both for the ultimate state as well as serviceability conditions. Initially conceptualized by Urs Meier, gradient anchorage offers an alternative to conventional mechanical anchoring techniques purely based on the bond between CFRP-epoxy-concrete. It is achieved by a segment-wise prestressing force release at the strip end after the accelerated curing of epoxy under high temperatures. The long-term behaviour is a significant factor for real-world applications due to the thermaland moisture sensitive nature of epoxy. Experimentally, it has been observed that FTC causes a reduction in the residual anchorage resistance and deformation capacity of the system. Moreover, the failure mode is switched from a concrete substrate to an epoxy-concrete interface failure. In order to accurately capture the failure mechanisms, a cohesive zone modelling (CZM) approach is herein. Zero-thickness cohesive elements are embedded between each continuum element, and subsequently constitutive traction-separation laws of the concrete substrate and epoxy-concrete interface are introduced. These laws are derived via an inverse analysis relying on experimental observations, obtained via digital image correlation. The CZM approach proves successful in accurately simulating the experimentally observed behaviour based on the provided tractionseparation curves