| The objective of this research is to develop a computational model for dynamic progressive collapse analysis of frame structures, particularly steel frames. Of particular interest is the evaluation of the alternate load path method, which currently forms the basis of several building codes for the design of structures to resist collapse, to determine if it is capable of accurately accounting for dynamic load redistribution following the failure of a structural component. Currently, the alternate load path method relies upon static analysis procedures for assessing performance.; A computer program developed specifically for this research accounts for the change in structural properties and configurations of a damaged frame as member failures occur. The analysis tool is capable of tracing the response of a structure from the point of initial damage to the collapse limit state under the imposed loads being considered. The software includes both geometric and material nonlinearities, and it incorporates a damage index so that the strength and stiffness degradation of the members can be modeled. Following the failure of individual elements, the software accounts for the possibility of impact with other members in a frame. Rigid body impact theory is used to represent the impact conditions.; While current building codes recommend the use of a static approach for implementing the alternate load path method, analytical results from this research demonstrate that dynamic effects strongly influence load redistribution, and, therefore, should be considered. Research results also indicate that impact effects resulting from falling failed members play a major role in causing member failures to propagate away from the original component failure location. Thus, engineers must be able to account for these effects if they are to design structures that have sufficient resistance to progressive collapse. |
