Radial elastic stiffness associated with bond between steel bars and concrete

Mechanical interaction between steel bars and concrete is sometimes idealiz ed in finite element analyses as an interfacial behavior: interface models that couple the tangent and normal responses can produce both pullout and s plitting failures. The ribs' wedging effect is represented by radial dilati on of the interface, which is composed of inelastic dilation and elastic co ntraction (representing local elastic deformations). The effective radial e lastic stiffness of the interface is related to reduced contact conditions that it accurately characterizes for a simple splitting model. A model (bas ed upon a concrete wedge on the rib face and experimental data) is presente d for estimating the contact length; it predicts the concrete wedge size an d other parameters qualitatively consistent with experimental results. Vari ation in elastic stiffness (due to differing contact conditions) is incorpo rated into an interface bond model, and the predicted radial responses of s elected bond specimens are improved by the more detailed treatment.