Aim: The aim of this paper is to show that fire development in a large-space steel commercial building may have a different intensity depending on the location in which the fire originated. Buildings of this type are usually characterised by a large area with a relatively low height, which makes air circulation and fire-gas evacuation difficult. The low value of the opening factor in this case is an additional constraint preventing fire from developing freely. All this makes a localised fire which has not reached a flashover and for which the fire-plume-gas temperature has not become uniform throughout the fire compartment a representative pattern which should be considered to assess the fire safety of such buildings.

Project and methods: This paper investigates the development of a localised fire which originates in three alternative locations differing in the position of the fire source and in the distance to the gate openings which ventilate the fire compartment. The FDS software is used for numerical fire modelling, specifying the time-varying spatial maps of the fire-plume-gas temperature on the basis of the equations taken from the fluid dynamics methodology with thermodynamic and aerodynamic variables.

Results: The presented results, obtained hitherto, involve a steel commercial building which has no smoke vents, which are legally required, and sprinkler systems or any other active fire protection solutions. The plan for future works is to include additional formal components for modelling purposes to explore the impact of these safety measures on fire development. The fire-plume-gas temperature profiles associated with the individual fire locations investigated are linked for comparative purposes to the corresponding results yielded by the analytical models recommended by the professional literature.

Conclusions: The obtained results seem to support the assertion that the modelling of a localised fire only on the basis of the existing analytical models does not necessarily lead to sufficiently reliable evaluations of the projected safety, particularly when this development depends on the factors which have not been accounted for in such models. An example of such a situation is the case investigated in this article, when the intensity of the anticipated fire depends on the location of the fire source, which involves varying oxygen availability necessary to sustain combustion.

Keywords: steel commercial building, localised fire, fire development, ventilation conditions, fire-plume-gas temperature, fire-source location

Type of article: original scientific article