Numerical modelling of fracture in polyolefin fibre reinforced concrete specimens under mixed-model loading (I+II)

In the last decades, many researchers have focused their work on studying the behaviour of fibre-reinforced concrete (FRC). The appearance of specific recommendations in several Standards has boosted their usage and the interest in this technology. Apart from the traditional steel fibres, new materials are now studied as fibre-type reinforcement in structural concrete. This is the case of polyolefin, a polymer that has proved to be a suitable alternative that overcomes some of the drawbacks of steel, namely those related to corrosion processes, and keeps a good ductile behaviour providing structural strength to concrete against tensile stresses. Modelling fracture of FRC elements has also proved to be successful using trilinear softening functions, not only with polyolefin fibres, but also with steel and glass fibres. Nevertheless, these numerical models have been used to contrast only notched specimens under three-point bending symmetric loading. In this contribution, trilinear softening functions are used to model fracture in specimens in which crack initiates under a combination of modes I and II. Fracture is modelled by means of an embedded crack formulation based on the strong discontinuity approach. Two sets of experimental data are compared, one with specimens of the same size with different proportions of fibres and another one where, keeping the fibre proportion constant, the specimens are scaled up in order to analyse the size effect. In both sets of experimental results, the Load-CMOD diagrams fit reasonably well using trilinear softening functions, predicting with correction the maximum load and the shape of the diagram due to the influence of the fibres.