Estimation of Structural Fire Vulnerability Through Fragility Curves

In the international scientific framework, the use of probabilistic and semi-probabilistic approaches to evaluate the fragility or the robustness of structures and infrastructures, is getting more and more common, especially in the field of seismic engineering. While, in the field of fire engineering, this approach is still little used, although it can be considered useful for design purpose. Therefore, in this work, to obtain the fire vulnerability of steel structures, the fragility curves were constructed, based on the results of many numerical simulations carried out on seismically and non-seismically designed steel frames. Cloud Analysis method was chosen by applying a regression in the logarithmic space of structural thermo-mechanical response, varying once the fire intensity and again the protection measures. The original idea of this work is to obtain fragility curves useful both for the fire vulnerability assessment of steel structures and for the optimal design of the fire-protection materials, to improve structural fire performance. The results show that, from the deformation point of view, the seismically designed steel structures are performer than non-seismically designed one. The fragility curves could be useful both for fire designers and fire protection manufacturers because they take into account, in a simplified way, the main uncertain parameters which can affect the structural fire behaviour.