Robustness Assessment of Multi-story Steel Frames in Post-earthquake Localized Fire Scenarios

Robustness of multi-story buildings, and more globally, of any construction, is an important matter when the safety of built environment is considered. However, as seen from past natural or human-made originated accidents, an improvement of the design process allowing us to ensure an appropriate structural robustness is still required. The consequences can be aggravated in case of cascading events, e.g., seismic aftershocks, explosion or localized fire after an earthquake. The study presented in the paper investigates the robustness of multi-story steel frames following the loss of a column. The case study structures were designed for the envelope of seismic and persistent design situation demands, considering low seismicity conditions of the site. For the perimeter locations, the structures had adequate resistance to prevent the progressive collapse, due to the large overstrength resulted in beams and joints from either non-seismic or seismic design situations. For the interior spans designed for gravity loads, the solution with partial strength joints also provided the capacity required to resist the loss of a column, with maximum load multipliers, λ, larger than unity. On the contrary, if the beams (and end connections) are designed to provide only the minimum tying resistance specified in the codes, the progressive collapse initiates.