Dynamic fracture modeling of concrete composites based on nonlocal multiscale damage model and scaled boundary finite element methods

Dynamic fracture is a critical concern in the design and reliability assessment of concrete structures. This study presents a numerical prediction of dynamic fractures in concrete composites using a nonlocal multiscale damage model and the scaled boundary finite element method (SBFEM). The nonlocal multiscale damage model accurately captures the damage behavior of concrete materials by considering the nonlocal effects and predicting fractures under dynamic loading conditions. The SBFEM combined with quadtree meshes, efficiently models and discretizes concrete composites, enhancing computational efficiency, and capturing local details. The concrete mesostructure consists of aggregates, mortar matrix, and interface transition zone. The random aggregates are generated using the popular Monte Carlo simulation and take-and-place methods. By slightly offsetting the boundaries of the generated aggregates, a virtual thickness interface is obtained to approximately characterize the weakest regions. This study extensively investigates the effects of loading rate, aggregate content and shape, and interface thickness on fracture properties. The loading rate significantly influences crack morphology, with low rates suppressing crack branching, and higher rates resulting in crack branching. Moreover, an increased aggregate content in the concrete results in greater maximum reaction force. Additionally, the range of the maximum reaction force is higher when polygonal aggregates are used as compared to circular aggregates. This study examines the impact of the interface thickness on the fracture characteristics. Increasing the interface thickness makes the interface region more fragile, resulting in additional minimally damaged areas alongside the completely damaged cracked sections. This behavior can be attributed to the energy degradation functions employed in the model, thereby decreasing the load-bearing capacity of these regions. These findings contribute to a better understanding of the dynamic fracture phenomena and aid in optimizing the design and improving the reliability of concrete structures.