Complete Triaxial Stress-Strain Curves of High-Strength Concrete

The axial-stress–axial-strain and axial-stress–lateral-strain behavior of concrete under active lateral confinement is presented. The uniaxial strengths investigated are 41.9 MPa, 60.6 MPa, 73.1 MPa, and 103.3 MPa. The confining pressures (σ3) used are 4 MPa, 8 MPa, and 12 MPa. Details of an economical lateral-strain-measuring device used in this investigation to produce accurate and repeatable measurements are presented. For low levels of confinement, the constant in the Mohr-Coulomb failure criterion (k) is shown to be closer to five than the traditional value of four. The axial strain at peak stress is shown to have a strong linear relationship with the level of confinement. Parameter values are suggested for Ottosen's constitutive model based on nonlinear elasticity. It was discovered that descending portion of the nonlinearity index (β) versus the secant value of Poisson's ratio (νa) was independent of the uniaxial strength and the level of confinement. A simple model is proposed for the descending portion of the β versus νa curves.