Local plastic surfaces for cracking and crushing in concrete

Abstract

The experimental failure envelope for concrete has the form of a curved Coulomb failure surface, which can reasonably be assumed to be related to a principal plane of shearing. This assumption is used in the development of a multiple surface plasticity model for concrete, in which the same local yield function is used to simulate directional fracture and isotropic compressive behaviour. A function is derived from experimental data that provides the transition from directional cracking behaviour to isotropic compressive behaviour. The local responses from all active plastic surfaces are coupled in a multisurface plasticity formulation, which provides the interaction between compressive and tensile behaviour in a natural way. The model is validated against experimental data from uniaxial and multiaxial compressive tests as well as tensile fracture tests. The model has been implemented in the finite element (FE) program LUSAS, and a summary of the implementation algorithm is provided. A number of stress path examples are considered, and the results from two FE analyses are presented.