Dissipation due to damage for an anisotropic 3D delay-damage model Application to reinforced concrete structures under impact loadings
Résumé
The problem of degradation of civil engineering structures under impact loading is a complex topic largely studied due to high industrial demand. Our approach consists in developing a robust Finite Elements model and the efficient algorithms associated so as to carry out 3D simulations on reinforced concrete structures. The model is an anisotropic damage model, written in the thermodynamical background, where the damage variable is a second order tensor [1,2]. One can this way reproduce the dissymetry observed for concrete between tension and compression, and reproduce crack patterns for quasistatic and slow dynamics loadings. To extend the model to dynamics loadings it is necessary to consider the strain rate effect which introduce a relation between strain rate in tension and the maximal strength. A delaydamage [3] (viscosity) law now governs damage evolution. The effect of delaydamage on regularization in dynamics will be shown. Experiments on a dropweight tower have been carried out to validate the results obtained numerically. Impact tests on two different reinforced concrete beams enable to show two different failure modes (bending and shear cone). Brazilian tests on plain concrete specimens have also been performed In both cases, numerical simulations and experimental results are compared. Image correlation is also used to interpret images recorded with an high speed numerical video camera. So as to better understand the phenomenons observed, we also propose a way to estimate dissipation due to damage [4]. This can be done thanks to the thermodynamical background that ensure than dissipation remain positive all the time [5]. Dissipation maps can be drawn and evolution curves plotted.
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