A smeared crack formulation for simulating fracture of fibre-reinforced concrete by means of a trilinear softening diagram

This study presents a smeared crack model for reproducing the fracture behaviour of FRC that is based on an embedded crack formulation used lately with this material. In both cases, a trilinear softening diagram allows reproducing the post-peak behaviour correctly. The model proposed here differs from the one on which it is inspired, since it is a smeared crack model based on the crack band concept where the material damage is isotropic and controlled by a damage factor ranging from 0 to 1, while the original model is an embedded crack model that allows fracture in three directions per element. This new formulation overcomes some limitations of the embedded crack model, that could only be used with triangular elements with an only integration point, since it can be used with triangular and quadrilateral elements with any number of integration points. Unlike previous models, developed for commercial codes, this model is developed in OOFEM, a free finite element code developed at the Czech Technical University in Prague (Czech Republic) and Chalmers University of Technology (Sweden), thus providing the general public with an advanced tool that allows reproducing fracture in structural elements made with fibre-reinforced concrete elements. This work shows that the proposed formulation provides similar results to those obtained with the model on which it is inspired under different situations: mode I fracture, size effect analysis and, finally, modes I and II mixed fracture.