Fragility analysis of steel moment frames with various seismic connections subjected to sudden loss of a column

In this study the progressive collapse potential of steel structures having WUFB, RBS, and WCPF connections was investigated considering the uncertainty in material properties such as yield strength, live load, and elastic modulus. The beam-end rotation was used as a member-level limit state for progressive collapse. Pushdown analyses of the model structure with three different connection types were carried out after removing one of the first-story columns. Fragility curves were obtained based on the probability of exceeding a given limit state for vertical displacement using the First-Order Second Moment (FOSM) method. The analysis results showed that the RBS connections showed the highest load resisting capacity against collapse due to their highly ductile behavior and that the loss of an exterior column turned out to be more vulnerable for progressive collapse than the loss of an interior column.