SUMMARYDiscretizing a domain of interest into a set of particles for discrete element simulation is the first step to generate a specimen. An improved algorithm, the Seed Expansion Method (SEM), is proposed in this work. A seed is first generated inside a given domain. Then, the domain is filled by the seed expansion based on a local Delaunay tessellation and a distance function. An optional operation, refilling, is suggested to further improve the packing density after the completion of SEM. Polydisperse dense packing can be generated by the proposed method for an arbitrarily shaped domain in both 2D and 3D. A specimen can be obtained that approximately conforms to a specified size distribution and packing density. Multiple subdomains of a domain can be filled by packings with different densities and size distributions. A specimen with higher density can be obtained by comparing it with the existing methods. Mathematically, the features of the method include both simplicity and high efficiency.

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In the field of disaster prevention mitigation and protection engineering, it is important to identify the mechanical behaviors of reinforced concrete (RC) under explosive load by simulation. A three dimensional beam-particle model (BPM), which is suitable to simulate the fracture process of RC under explosive load, has been developed in the frame of discrete element method (DEM). In this model, only the elastic deformations of beams between concrete particles were considered. The matrix displacement method (MDM) was employed to describe the relationship between the deformation and forces of the beam. A fracture criterion expressed by stress was suggested to identify the state of the beam. A BPM for steel bar, which can simulate the deformation of steel bar under high loading rate, was also developed based on the Cowper-Symonds theory. A program has been coded using C++ language. Experiments of RC slab under explosive load were carried out using the program. Good agreement was achieved between the experimental and simulated results. It is indicated that the proposed theoretical model can well simulate the fracture characteristics of RC slab under explosive load such as blasting pit formation, cracks extension, spallation formation, etc. explosive load, reinforced concrete slab, beam-particle model, steel bar, high loading rate, fracture Citation:Liu J, Zhao C B, Yun B. Numerical study on explosion-induced fractures of reinforced concrete structure by beam-particle model.

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