Mesoscale numerical study of size effect on concrete fracture characteristics based on FDEM

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Fracture characteristics of concrete remains a focal point of current research. Traditional experimental approaches and finite element simulations face limitations in the study of concrete's fracture behavior. The novel combined finite-discrete element method (FDEM) offers pronounced advantages for investigating concrete fracture at the mesoscopic scale. In this paper, utilizing the FDEM approach, a mesoscale concrete model encompassing aggregates, mortar, and the interfacial transition zone was constructed. Three-point bending simulations on concrete beams with precast cracks revealed the mesoscopic fracture processes and characteristics. Results showed that as beam height increases, the fracture energy of the specimens first increases then decreases, and the ductility index decreases. Additionally, as the crack height ratio increases, the beam's fracture energy gradually lowers, while the ductility index initially rises then falls. This study provides insights into beam fracture mechanisms and properties, contributing to the failure analysis of concrete structures at the engineering scale.