Comparison of Various Procedures for Progressive Collapse Analysis

We compare four methods for progressive collapse analysis by analyzing a nine-story steel moment-resistant frame building, employing increasingly complex analytical procedures: linear-elastic static, nonlinear static, linear-elastic dynamic, and nonlinear dynamic methodologies. Each procedure is thoroughly investigated and common shortcomings are identified, along with advantages and disadvantages, using side-by-side comparison, including approximate time spent on modeling and computation. The evaluation uses current General Services Administration progressive collapse guidelines. Our objective is to provide clear conceptual step-by-step descriptions of various procedures for progressive collapse analysis by performing example analyses using commercially available structural analysis software, such as SAP2000, with the aim that the explanations in this paper will be clear enough that they will be readily understandable and will be used by practicing engineers. We demonstrate that dynamic analysis procedures not only yield more accurate results, but are also easy to perform for progressive collapse determination. Additionally, we show that current GSA performance limits for linear analysis procedures are unconservative, meaning that a structure designed with acceptable linear evaluation criteria may exceed allowable ductility and rotation limits when nonlinear dynamic analysis is performed on the same structure. Finally, our recommendations for the analysis procedures take into account accuracy as well as ease of use.