Three dimensional nonlinear model of beam tests for bond of near-surface mounted FRP rods in concrete

The use of near-surface mounted FRP reinforcement in reinforced concrete structures has seen a considerable increase in recent years as a strengthening method. Beam pull-out tests for near-surface reinforcement allow obtaining the local bond–slip behavior of a bonded joint. The current paper deals with the three-dimensional modeling of this kind of test with the purpose of suitably characterizing the mechanics of the bond between FRP rods and concrete. Different alternatives to represent the FRP bar – concrete interface have been evaluated. Furthermore, to do this modeling, a PID controller has also been designed to conduct the numerical tests correctly in order to properly capture the softening branch of the load-slip behavior. The numerical FE simulations were compared with previously published experimental measurements. Load-slip predictions compare well with the corresponding experimental data. The proposed model is also able to predict the failure mode at the FRP-concrete interface. Some parametric studies have also been carried out.