Application of criteria for selecting fire scenarios for structures within fire safety engineering approach

This paper deals with a crucial aspect of the application of Fire Safety Engineering (FSE), which is the definition of fire scenarios and the choice of the design ones for structures. FSE requires, moreover, the choice of performance levels, fire models and, generally, advanced thermo-mechanical analyses. The number of possible fire scenarios is usually too large and the analysis of each one is not practicable. Therefore, the design fire scenarios should be chosen, in order to analyse the most severe cases for the structure. The choice of the design fire scenarios could be carried out through two possible procedures, shown in this paper: a) the Fire Risk Assessment (FRA), whereby a proper estimation of the Risk associated to each fire scenario is conducted; b) the procedure proposed in EN1991-1-2 (Annex E), whereby a single group of design fire scenarios is defined, taking into account the phenomena capable to modify the fire development, by introducing some coefficients in the calculation of the fire density load. In this paper, the main concepts of the two methodologies are shown and discussed and a comparison is proposed referring to a case study, inspired to an existing office building.