The events of September 11, 2001, along with the previous bombing of the World Trade Center, and the bombing in Oklahoma City, show the need for the US to be prepared for man-made disaster events and to be able to recover quickly in the event of an attack. These events are very similar to natural disasters in that there is limited prediction and potential large economic impact and loss of life. Computational mechanics and non-linear, dynamic, 3-D computer codes are used in research to develop reliable assessment tools for progressive collapse of structures. It occurs when a structure experiences a localized damage, which initiates a chain reaction resulting in unexpected changes of the loading pattern. As a result, other structural elements are loaded beyond their capacity and fail. One of the examples of the progressive damage is the collapse of the World Trade Center Towers in New York on September 11, 2001. It is clear that the global collapse of the towers was initiated by local damage due to aircraft impact and fire. High explosive material can be virtually detonated either outside of the structure or within the structure resulting in its progressive collapse.