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Progressive collapse of framed structures is a complex topic going beyond the usual tools of structural mechanics. The analogy with the propagation of damage in the framework of fracture mechanics has already brought some theoretical results, especially when the energy fluxes are analyzed. Nevertheless, the difficulty to get representative experimental data avoids proposing and eventually proving the effectiveness of new theories modeling collapsing frames with equivalent homogeneous cracking continua (or foams). Therefore, reliable computer simulations based on widely accepted methods are necessary. Since traditional FEM are inapplicable when a structure looses rigidity, DEM have been used to run the simulations shown throughout this paper. The advantages, the limits and the problems of this approach are discussed and particular attention is paid to the effects of impacts between falling elements and the structural members.