Evaluation of Concrete Cylinder Tests Using Finite Elements

Nonlinear axisymmetric finite element analyses are performed on the uniaxial compressive test of concrete cylinders. The models include thick steel loading plates, and cylinders with height-to-diameter ratios (h/d) ranging from 1–3 are treated. A simple constitutive model of the concrete is employed, which accounts for the strain hardening and softening in the pre- and postfailure regions, respectively. When h/d = 2, the failure mode is found to consist of undisturbed end cones and the occurrence of strain softening, especially in the outer region of the cylinder middle. For shorter cylinders the strain softening is more pronounced along the surface of the cylinder middle, whereas longer cylinders exhibit a more uniform distribution of strain softening. The failure modes for force and displacement controlled tests are found to be similar. If long cylinders are to provide the true uniaxial strength the use of geometrically matched loading plates seems to be advantageous. Finally, it is observed that for variations of the element size within limits otherwise required to obtain a realistic analysis, the results are insensitive to the element size.