ABSTRACT
Abstract The non linear behaviour of concrete-like materials in tension is characterised by strain-softening. Phenomena involving the localisation of strains caused by strainsoftening can be analysed accurately through the so-called "cohesive crack model" which uses the length of the fictitious crack as a control variable. In this approach, the length of the process zone is not fixed and the ratio between this length and the length of the specimen decreases with increasing size-scale. This phenomenon is evident even for small changes in size. It can explain why the softening branch becomes steeper with increasing size-scale so that a critical size exists beyond which a cusp catastrophe occurs (snap-back), in both Mode I and Mixed-Mode problems. In other words, it can be stated that scale effects observed in the structural response depend on scale effects in the process zone.
