ECCM 2010 IV European Conference on Computational Mechanics Palais des Congrès, Paris, France, May 16-21, 2010 Discrete Element Modeling of the RC Structures under Severe Impact S. Potapov 1 , J. Rousseau 2 , P. Marin 3 , L. Daudeville 3 1 LaMSID UMR EDF/CNRS, France, serguei.potapov@edf.fr 2 EDF R&D, Clamart, France, jessica.haelewyn@edf.fr 3 3S-R (Soils, Solids, Structures – Risks),UJF/INPG/CNRS, France, laurent.daudeville@ujf.fr, philippe.marin2@hmg.inpg.fr To assess the mechanical consequences of impact loads on reinforced concrete (RC) structures, EDF R&D develops numerical methodologies allowing a multi-level analysis within the computational framework of the EUROPLEXUS fast dynamics software [1]. Through an appropriate space-time coupling of different numerical methods and formulations (see [2], [3]), it is possible to take into account both locally discontinuous behavior (fractures, fragmentation) of the impacted structure and the globally elastic response of the whole reinforced concrete building. To represent a highly nonlinear local behavior of the structure in the impact zone and to obtain a detailed description of the fracture and fragmentation mechanisms we use a Discrete Element Method (DEM) [4]. DEM is appropriate to model discontinuities because it does not rely on any assumption regarding where and how a crack or several cracks occur and propagate. Both media – concrete and steel – are considered as discontinuous with inter-element interaction defined either through constitutive laws (before breaking) or through contact relations (after breaking). Concrete is represented by a compact assembly of discrete (spherical) elements of different sizes. This assembly must be polydisperse with a given size distribution, be dense enough, and isotropic. The reinforcement bars (longitudinal and transversal) are modeled by means of aligned single “steel” discrete elements whose diameters correspond to those of the real reinforcement. The local behavior of steel is considered as elastic, perfectly plastic, whereas the interaction law for concrete is chosen to obtain a quasi-brittle macroscopic behavior. A special interaction law is introduced to model concrete- steel bond. To evaluate the capability of the DEM model developed, we simulate the test n° 5 of the MEPPEN test campaign dealing with impact of soft missiles on RC slabs [5]. The slab of 6.5 m by 6 m and 70 cm thickness is impacted by a tube-like missile (6 m length, 60 cm diameter) at 235 m/s. The DE model of the slab we use contains about 193.000 “concrete” and 63.000 “steel” elements (Figure 1). In the present simulation the projectile is represented by a Riera-type force applied through a flexible disc at the centre of the slab. Figure 1: DE model of the MEPPEN slab: concrete and loading disc (left), reinforcement (right). 1