Numerical Evaluation and Prediction of Bond Performance of Ribbed FRP and Steel Bars in Concrete Using Pull-out Test Simulations

Abstract

This research investigates the bond behavior between concrete and ribbed reinforcement bars through numerical simulations of pull-out tests, focusing on three types of fiber-reinforced polymer (FRP) bars—Glass (GFRP), Aramid (AFRP), and Carbon (CFRP)—alongside conventional Steel bars, all with diameters ranging from 10 to 14 mm. Steel bars are modeled using a bilinear elastic–plastic constitutive law, while FRP bars follow a linear elastic behavior. The concrete modelled using a Regularized Coupled Damage–Plasticity Drucker–Prager Microplane approach. The interaction between concrete and reinforcement is simulated using a Mohr–Coulomb-type contact interface with friction coefficients tailored to each bar material, also accounting for mechanical interlock through explicit modeling of the rib geometry. The simulation results from the pull-out tests are compared against analytical bond–slip models and predictive formulations for maximum bond stress reported in the literature. Based on these comparisons, a new adapted predictive analytical model is proposed, showing improved agreement with the simulation data. The results indicate that CFRP bars exhibit in general the highest bond stress performance, followed by AFRP, steel, and GFRP. For all bar types, both the maximum bond stress and the corresponding slip decrease with increasing diameter. Steel bars exhibit higher and less predictable slip as a result of plastic deformation, whereas FRP bars demonstrate more stable and predictable behavior owing to their linear elastic response.