Disturbed stress field model for reinforced concrete: Formulation

A conceptual model is presented for describing the behavior of cracked reinforced concrete elements, representing a hybrid formulation between a fully rotating crack model and a fixed crack model. The formulation described builds on the concepts of the modified compression field theory, treating cracked concrete as an orthotropic material with unique stress-strain relationships in compression and tension. Advancements in the formulation, relative to the modified compression held theory, include a new approach to the reorientation of concrete stress and strain fields, removing the restriction that they be coincident, and an improved treatment of sheer stresses on crack surfaces. New sets of equilibrium, compatibility, and constitutive relations are formulated accordingly, and alternative crack slip models are discussed. The proposed theory is shown to yield improved simulations of response in specific situations where the previous formulation was found to produce inaccuracies. This paper describes the formulation of the theory at the fundamental level.