N. Oudni et alii, Frattura ed Integrità Strutturale, 35 (2016) 278-284; DOI: 10.3221/IGF-ESIS.35.32 278 Focussed on Crack Paths Implementation of a damage model in a finite element program for computation of structures under dynamic loading Nasserdine Oudni Department of civil engineering, faculty of technology, A. Mira University, Bejaia, Algeria Laboratory of modeling of materials and structures, University of Tizi-Ouzou, Algeria nasroudni@yahoo.fr Youcef Bouafia Laboratory of modeling of materials and structures, University of Tizi-Ouzou, Algeria youcef.bouafia2012@yahoo.com A BSTRACT . This work is a numerical simulation of nonlinear problems of the damage process and fracture of quasi-brittle materials especially concrete. In this study, we model the macroscopic behavior of concrete material, taking into account the phenomenon of damage. J. Mazars model whose principle is based on damage mechanics has been implemented in a finite element program written Fortran 90, it takes into account the dissymmetry of concrete behavior in tension and in compression, this model takes into account the cracking tensile and rupture in compression. It is a model that is commonly used for static and pseudo-static systems, but in this work, it was used in the dynamic case. K EYWORDS . Damage; Dynamic; Modeling; Displacement; Strain; Local approach; Time integration; explicit; quasi-brittle. I NTRODUCTION he numerical program is employed in analyzing Koyna gravity dam and comparing the results with available results of many researchers find in literature. The choice of Koyna concrete gravity dam is due to the fact that many studies have been done on this structure which experienced a devastating earthquake in 1967. Since Koyna dam in the 1967 Koyna earthquake [1-4] is one of the few examples of cracking in a concrete dam, it has been selected to investigate its earthquake response. The earthquake records are in the form of accelerograms with horizontal and vertical components which are used as dynamic loads. The effect of the damping coefficient is obviously taken into account. This work proposes the implementation of a damage model based on the damage mechanics as part of the isotropic formulation proposed by J. Lemaitre in a finite element program. the J. Mazars model [5] whose principle is based on damage mechanics which is a theory describing the progressive reduction of the mechanical properties of a material due to initiation, growth and coalescence of microscopic cracks. These internal changes lead to the degradation of mechanical properties of the material. The model takes into account the asymmetry of concrete behavior and it considers the cracking in tension and compression failure. The method is based on the notion of equivalence of the strains. T

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