Abstract
A combined finite/discrete element method is proposed for the prediction of reinforced concrete structure response under severe dynamic lo ads as impacts due to natural or anthropic hazards. A bridging subdomain is used, the Hamiltonian is chos en as a linear combination of discrete and continuu m Hamiltonians. Discrete Element displacements and rotations are linking to Finite Element displacements by means of Lagrange multipliers. The discontinuiti es of discretization introduce spurious reflection ; numerical methods are proposed to attenuate it. The modeling of the whole structure under such impacts needs on one hand a model able to describe the occurrence of severe damage (fragmentation, spa lling, tunneling) in the zone of impact, and on another hand a model able to capture the global res ponse of the structure. The study aims at showing how the proposed combined finite/discrete element method satisfies both conditions. Locally, the discrete element model deals with nonlinear phenomena, far from impacted zone the finite element method allows the reduction of both times of modeli ng and computation. Using the combined method allows the prediction of projectile penetration, st ructural damage and global displacements. The efficiency of DEM to study rocks, plain concret e and reinforced concrete has already been shown in 2D, Camborde (1), Potyondy (2) and in 3D, Hentz (3). The applications of DEM to large scale structures were limited due to computing costs; the number of elements increase reduces drastically computational efficiency. To improve that point, th e region without any assumed damage is modeled by means of the FEM. The same media is model with two different methods; the discretization size at the interface is discontinuous. In the vicinity of impact the DE discretization is fine, whereas FE s ize is adapted to the structural scale and is larger th an DE. Discretization discontinuity induces spuriou s reflections.
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