Stress-Strain Relationship for Concrete Confined by Rectilinear Reinforcement: A Stiffness Degradation Approach

Square tied concrete prisms were tested under uniaxial concentric compressive load. Test variables were the tie spacing and diameter (3 levels each). Based on the observed degradation of the prism’s longitudinal stiffness, a simplified analytical stress-strain relationship was derived. The proposed model takes into account the effect of the tie spacing and diameter on the prism’s tangent stiffness, as well as the maximum stress and corresponding strain. Comparison of the analytical and experimental stress-strain diagrams indicated a very good correlation.