Robustness assessment for progressive collapse of framed structures using pushdown analysis methods

The issue of robustness assessment for progressive collapse of structures has been paid much attention to in the community of civil engineering since the 9/11 event. In this paper, both deterministic indices and reliability-based indices are introduced to quantify the robustness of a structure. The conventional deterministic pushdown analysis is improved to take into account the loading scheme for simulating column loss. To consider stochastic system properties, a random pushdown analysis is proposed by an improved point estimation method based on Nataf transformation. By using the developed pushdown methods, the reserve load carrying capacity of the damaged structure is evaluated, the robustness for resisting progressive collapse of the damaged structure is quantitatively assessed and the key element to be removed which is critical to structural global performance is identified. A code-conforming reinforced concrete frame structure is taken as a case study to demonstrate the applicability of the newly developed methods.