  The aim of this paper is to propose a novel methodology to deal with
micro-structural boundary conditions for the analysis of granular materials.
The response of the granular assembly is modelled through the discrete element
method (DEM), consistent with a micro-macro homogenization scheme formulated in
the transition from a continuous to a discrete setting. The three classical
types of boundary conditions (displacement, periodic and displacement) are
implemented with a servo-control method. Two types of algorithms are developed,
which consider or not an initial prediction for the displacement field of the
particles. Additionally, to simulate in a more realistic manner the effect of
macroscopic deformation on the micro-structure, a mixed type of boundary
conditions is introduced, i.e. a combination of classical boundary conditions.
The effectiveness of the algorithms is tested on a series of DEM simulations.
The influence of the micro-structural morphology and of the size of the
micro-structure on the overall response is finally investigated.
