1. Introduction

The law of behavior JOINT_BA describes the phenomenon of degradation and rupture of the existing bond between steel bars (smooth or ribbed) and the concrete surrounding them. A key point for the design of reinforced concrete structures, the modeling of the steel-concrete bond aims to represent and simplify this complex phenomenon of interaction between the two materials that develops at the interface and which undergoes increasing degradation when certain resistance thresholds, specific for each material, are exceeded. Structural models that do not take into account the effects of the connection are generally unable to predict the location of cracks as well as the networks created. Moreover, the deterioration of the stiffness of the bond increases the vibration period, reduces the energy dissipation capacity and leads to a significant redistribution of internal forces (according to Bertero, 1979, cf. [bib2]).

The law of behavior JOINT_BA is described in the context of the thermodynamics of irreversible processes: the writing and use of a « classical » model of material combining cracking and friction makes it possible to integrate in a robust manner fine non-linear mechanisms concomitant to the particular description of sliding kinematics. This last point allows us not to use the classical “contact” models that are often used in this context despite the numerous sources of numerical instabilities. Thus, under monotonous loading, taking into account the normal force — shear coupling makes it possible to treat cases of strong multiaxial stresses; in cyclic, the hysteretic behavior and the corresponding dispersions are expressed thanks to the coupling between the state of damage and the kinematic work hardening. The use of an implicit schema makes it possible to obtain a robust implementation.

Paragraph [§2] describes in brief form the phenomenon of the steel-concrete bond. Paragraph [§3] presents the thermodynamic writing of the law of behavior, while paragraph [§4] specifies the numerical integration step of the law. The parameters that manage the model and that can be obtained from the properties of the materials involved, are described in paragraph [§5].