Strain-gradient finite elasticity solutions to rigid bar pull-out test

The pull-out test is one of the common experiments to determine the bond strength. When the problem is modeled in the context of linear elasticity for a cylindrical reinforced concrete block, the resulting simplified 1-D model yields so-called pull-out paradox Rezaei et al. (Mech Res Commun 126:104015, 2022) due to extreme concentration of energy near the bar. Since the standard linear elasticity is not able to consider this high values of energy, the problem was investigated by strain-gradient elasticity solution in the work of Rezaei et al. (Mech Res Commun 126:104015, 2022). In this study, to resolve the paradoxical solution, classical finite (i.e., St.-Venant–Kirchhoff model) and strain-gradient finite elasticity solutions are presented. Each mathematical model, assuming that the material is isotropic, is derived with the principle of minimum potential energy introducing appropriate strain energy. The numerical simulations are performed by the finite element method, and it is showed that numerical solution of each model converges well.