The Post-fire Assessment of Steel Structures, a Reliability-Based Semi-probabilistic Approach

For the post-fire safety evaluation of metal structures or parts thereof, we still rely too often on experiential and non-scientific methods, as there exists today no transparent approach allowing to perform this using reliability-based approaches. Nevertheless, hundreds of tests have been carried out in the past on carbon and stainless steels samples that have been subjected to a heating and subsequent cooling procedure. Unfortunately, up to now, these data were not processed in a statistical way and there exists no elaborate method allowing designers to assess structural safety after a fire has occurred in an existing structure. In this research, we have solved this issue by analysing the variation in material properties of metals over time, as a function of the maximum reached temperature, and by proposing a modified reliability factor adapted to the study of existing buildings. The method is explained in detail and provided with the necessary practical information so that it is straightforwardly usable by all those involved in a post-fire evaluation. In the end, a practical example is used to illustrate the differences between carbon and stainless steels, the post-fire behaviour of which were analysed.