Creep model for the long-term behaviour of combined cohesive-bridging model of FRP–concrete interface debonding under axial loading

Numerical Modelling of the Nonlinear Shear Creep Behavior of FRP-Concrete Bonded Joints

“…In EB-FRP applications, service loads are transferred from the concrete structure to the FRP reinforcement through the adhesive joint, which deforms mainly under shear stress. Due to its inherent viscoelastic nature, the polymer adhesive layer may exhibit substantial creep deformation when subjected to sustained shear load, hence affecting the stress transfer process between the host structure and the FRP material [ 13 , 14 , 15 , 16 ]. This creep effect is possibly emphasized by the evolution of the adhesive properties (loss of stiffness) due to environmental ageing under service conditions [ 17 , 18 ].…”

“…The viscoelastic response of bulk polymer materials has been widely investigated in the literature, through both experimental studies and theoretical approaches. Experimental works rely most often on tensile tests at constant load levels [ 16 , 21 , 22 , 23 ] although few authors have developed specific setups to investigate the creep behavior of bulk polymers subjected to sustained shear loading [ 24 ]. Differently, the creep behavior of the adhesive joints in FRP-concrete assemblies is less documented.…”

“…Finally, this behavior law was successfully implemented in a FE model to predict the creep response of FRP-concrete bonded assemblies. Besides, Houachine et al [ 16 ] proposed an analytical model to describe the long-term load-bearing capacity of concrete beams strengthened with EB-FRPs, which includes the creep contributions of all component materials (i.e., concrete, adhesive and FRP). A combined cohesive-bridging zone model was then proposed to model both the crack-processing zone near the interface (cohesive zone model) and the particle-interlocking region (bridging zone model).…”

“…Hadjazi et al [ 30 ] also studied the long-term behavior of RC beams strengthened by EB-FRPs, but with a particular focus on the time evolution of shear stresses induced by flexural cracks along the adhesive joint. In continuity with previous works [ 16 , 31 ], these authors considered the creep behaviors of all the component materials of the retrofitted beam to develop an original viscoelastic model, in which the influence of environmental conditions are introduced through adjusted creep factors depending on the relative humidity. It is noteworthy that Eurocode 2 [ 32 ] suggests the construction of a creep function based on the creep behavior laws of all component materials of the bonded assembly (concrete, adhesive and FRP).…”

Flexural stiffness analysis of concrete elements with composite reinforcement under repeated load and elevated temperature

“…The incomplete epoxy hardening under ambient conditions renders EBR vulnerable to specific deterioration mechanisms, substantially reducing the modulus of elasticity, strength, and glass transition temperature (Blackburn et al, 2015). These effects are environment-and time-dependent, complicating the composite behavior (Houachine et al, 2022;Korkmaz, Gültekin, 2022;Faysal et al, 2023). From the macroscopic consideration point, a transition (interphase) region can be separated from the contact (interface) zone between the epoxy and concrete bulk substrates (Tatar et al, 2018(Tatar et al, , 2019.…”