A new constitutive model for concrete-steel bond behavior

In the present work, the load transfer mechanisms between concrete and steel reinforcement are modeled through a four node axisymmetric finite element which represents the behavior of a layer of material of vanishing thickness. The constitutive model directly relates the interface stresses (normal and tangential) to the displacements (opening and slip) and takes into account the most important physical mechanisms, including softening, confinement, etc. Numerical simulations of pull-out tests for confined and unconfined specimens are then presented, in which the concrete is modeled by through the microplane M4 model. The results of these simulations show a good agreement with the available experimental data.