Finite Element Analysis of Concrete Fracture Specimens

Abstract

The effects of the descending branch of the tensile stress-strain curve, fracture energy, grid refinement, and load-step size on the response of finite element models of notched concrete beams are studied. The width of the process zone and constraint of crack angles are investigated. Nonlinearity is 1 imited to cracking of the concrete. A limiting tensile stress criterion governs crack initiation. Concrete is represented as linear elastic prior to cracking. Cracks are modeled using a smeared representaion. The post-cracking behavior is controlled by the shape of the descending branch, fracture energy, crack angle, and element size. Unloading occurs at a slope equal to the i nitia 1 modulus of the material. load deflection curves and cracking patterns are used to evaluate the beam's response. Comparisons of the process zone size are made. All analyses are performed on a 200 x 200 x GOO mm concrete beam, with an initial notch length of 80 mm. The fracture energy, tensile strength, and shape of the descending branch interact to determine the stiffness and general behavior of the specimen. The width of the process zone has a negligible influence on the beam's response. The importance of proper crack orientation is demonstrated. The model is demonstrated to be objective with respect to grid refinement and load-step size.