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Introduction of imperfections in the cubic mesh of the truss‐like discrete element method
Author(s) -
Iturrioz I.,
Riera J. D.,
Miguel L. F. F.
Publication year - 2014
Publication title -
fatigue and fracture of engineering materials and structures
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.887
H-Index - 84
eISSN - 1460-2695
pISSN - 8756-758X
DOI - 10.1111/ffe.12135
Subject(s) - truss , softening , tension (geology) , compression (physics) , structural engineering , materials science , nonlinear system , constitutive equation , displacement (psychology) , discrete element method , mechanics , fracture (geology) , finite element method , stress (linguistics) , composite material , engineering , physics , psychology , psychotherapist , linguistics , philosophy , quantum mechanics
ABSTRACT In the present version of the truss‐like discrete element method (DEM), masses are considered lumped at nodal points and interconnected by means of unidimensional elements with arbitrary constitutive relations. In previous studies of non‐homogeneous concrete cubic samples subjected to nominally uniaxial tension, it was verified that numerical predictions of fracture using DEM models are feasible and yield results that are consistent with the experimental evidence so far available, including the prediction of size and strain rate effects. In the DEM formulation, material failure under compression is assumed to occur by indirect tension. In previous simulations, it was verified that the response is satisfactorily modelled up to the peak load, when a sudden collapse usually occurs, characteristic of fragile behaviour. On the other hand, experimental stress versus displacement curves observed in small specimens subjected to compression typically present a softening branch, in part due to sliding with friction of the fractured parts of the specimens. A second deficiency of DEM models with a perfectly cubic mesh is that the best correlations with experimental results are obtained with material parameters that differ in tension and compression. This paper examines another cause of the excessively fragile behaviour of DEM predictions of the response of concrete elements subjected to nominally uniaxial compression, which is due to the regularity of the perfect cubic mesh, unable to capture nonlinear stability effects in the material. It is shown herein that the introduction of small perturbations of the DEM regular mesh significantly improves the predicting capability of the model and in addition allows adopting a unique set of material properties, which are independent of the nature of the loading.