Analysis of Orthotropic Reinforced Concrete Structures

A mathematical model is derived for stress-strain properties of reinforced concrete. The model is obtained form stress-strain relations of reinforcing steel and plain concrete, and from considering slip in bond between them. The stress-strain relations for plain concrete are based on experimental data obtained under uniaxial, biaxial and triaxial compressive stress, and biaxial tensile and compressive stress. The model stress-strain relation in each principal stress direction is affected by the other two prinicpal stresses. The form of the stress-strain relation and the manner in which it is affected by the lateral principal stresses is different in tension and compressoin. A bilinear tensile-stress-strain relation is used to represent the elastic-plastic properties of the reinforcing steel. Until cracking occurs, properties of the model depend entirely on the concrete. After cracking, a composite modulus is used which reflects the combined stiffness of steel and concrete and takes into account the extent to which bond between steel and concrete is broken.