“…The first method is to generate aggregates by randomly throwing the geometries [11,12,13,14], and the other method is to regenerate the original structure based on the tomography of concrete [15,16,17]. The second issue is to calculate the built up model, and many methods have been adopted, such as traditional finite element method [18,19], the lattice model [20,21,22], the homogeneous model (such as meso-element equivalent method) [23,24,25], the extended finite element method [26,27], and the scaled boundary finite element method [28,29,30]. The discrete element methods are also considered, such as the particle flow method [31,32,33] and the rigid-body-spring method [34,35].…”