Radial elastic stiffness associated with bond between steel bars and concrete

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