Triaxial Stress-Strain Relationship for Concrete

A triaxial constitutive law and a failure criterion for concrete under short-term monotonic loading are derived from the analysis of available experimental data. Their representation through the octahedral normal and shear components of stresses and strains show that the deformational behavior of concrete can be described through simple analytical expressions relating the bulk and shear moduli to the first two invariants of the strain state. The values of the tangent moduli are then immediately obtained by differentiation. The ultimate strength criterion has been expressed as a relation between octahedral shear and normal stresses at failure involving also the third stress invariant. The proposed equations both for the constitutive law and the failure criterion are in a satisfactory agreement with experimental data and are suitable for use in numerical schemes for predicting the response of reinforced concrete three-dimensional structures.