A direct discrete formulation suitable for the nonlinear analysis of masonr
y structures is presented. The numerical approach requires st pair of dual
meshes, one for describing displacement fields, one for imposing equilibriu
m. Forces and displacements are directly used (instead of having to resort
to a model derived from a set of differential equations). Associated and no
nassociated flow laws are dealt with within a complementarity framework. Th
e main features of the method and of the relevant computer code are discuss
ed. Numerical examples are presented, showing that the numerical approach i
s able to describe plastic strains, damage effects and crack patterns in ma
sonry structures.