Relevance of displacement softening model in discrete element method to investigate structural and grain size scaling effect

Abstract

A local crack opening displacement softening model is used in the framework of discrete element method to investigate the fracture propagation and post-peak behaviour of concrete that remains a problem in the linear parallel bond model. Modelling approach is validated for mechanical behaviour by three-point bending tests on mortar and concrete. The numerical fracture propagation is compared with the damage pattern obtained using acoustic emission and digital image correlation techniques. In the three phase concrete microstructure, a comprehensive approach is used to determine the model parameters from laboratory tests and literature. The model is then applied to study the variation of aggregate size on fracture behaviour using three different concretes where only aggregate sizes were scaled. The results are compared with experiments. The model is further tested to investigate effect of specimen size and compared with experimental results. It is shown that softening model in DEM can effectively reproduce concrete behaviour and complex fracture process.