Damage from abnormal loading such as explosion, bombing, and sudden external impacts on elements of a structure can range from a loss of individual elements to total collapse. Progressive collapse has been a concern for many years, but recent acts of terrorism including the destruction of the World Trade Center and major damage to the Pentagon have renewed demand for methods to improve behavior of structures under these abnormal events. Progressive collapse can be defined as damage disproportional to the triggering mechanism. Design of structures against progressive collapse has not been an integral part of structural design. However, some codes such the GSA and UFC guideline have detailing requirements to reduce the likelihood of progressive collapse. It is difficult to predict the manner in which progressive collapse will propagate because the nature of loadings or triggering events are not well defined, and behavior of structural elements during a progressive collapse is not understood. In this study, three-dimensional nonlinear static and dynamic analyses of structures prone to progressive collapse are vii conducted using commercially available programs. The analysis is assumed to be independent of the cause of damage. The initial objective is to simulate structural behavior when load-carrying members are removed under the effects of abnormal loadings. After the critical member is removed, redistribution of the forces to other elements is investigated. In addition, the capability of resisting redistributed loads is examined to determine if adjacent elements participate in producing a progressive collapse. Dynamic effects due to removal of a critical column suggested by the GSA and UFC guidelines are compared with analytical results. The response of a robust structure is compared with the response of a structure with deficient details. When a critical column is removed, structural details related to connections, insufficient transverse reinforcement for shear in beams, and lap splices in columns are studied to demonstrate how components may be affected by removal of critical elements.