Risk-based robustness assessment of steel frame structures to unforeseen events

A risk-based robustness assessment approach of a steel frame structure affected by unforeseen events is developed. The approach quantifies both the failure consequence index and failure probability index and assesses the structural robustness of real steel frame structures. The separateness is used as the failure consequence index and determined by identifying the key components and possible collapse modes of the damage structure via a structural vulnerability analysis. The failure probability index is determined based on a hazard collapse potential, which is used to create the collapse probability-hazard collapse potential (P-H) fragility function. Then, the collapse probability of the damage structure is obtained by substituting the most disadvantageous hazard collapse potential into the P-H fragility function. The proposed approach is used to assess the structural robustness of a 4-story steel frame structure subjected to unforeseen events. The results show that the separateness quantifies the transformational relationship of the failure consequence index in the failure process, and the collapse mode of the damage structure with the largest hazard collapse potential is most likely to occur. The robustness results produced from the proposed approach are consistent with the conceptual results of structural mechanics, thus the validity of the approach is demonstrated.