In the past decades structural robustness has become an important issue among civil engineering studies, in the light of what has happened in terms of accidental events like the World Trade Center terrorist attack (New York, 11th September 2001). Normally, buildings are designed to withstand to normal actions, whose types and intensities are defined according to the building’s importance. Nevertheless, when an action is unlike to occur, or when it occurs whit a larger intensity than in normal scenarios, the building cannot resist to this event and a collapse can occur. When the facility is able to avoid disproportionate collapse, if a local damage occurs after an accidental event, the structure is judged robust from a structural point of view.