The challenges of prescribing an appropriate design fire for the structurally safe design of contemporary architecture
Large open plan configurations typical of tall buildings are considered as a staple of contemporary architecture as the built environment continues to stray further away from the concept of traditional compartmentalisation. The provision of fire safe solutions rely upon the understanding of fire behaviour and the heat loads experienced by the structure. Structural fire designs have traditionally been based on prescribing design fires such as the Standard Fire (ISO-834), or more recently the Parametric Fires, and the Compartment Fire Framework. These design fires are the result of decades of research into under-ventilated fires in small cubic compartments. These design fires are intended to provide practitioners with a conservative quantification of thermal conditions for a fully-developed compartment fire in under-ventilated conditions. The bounds of limitations for these design fires is quite clear in the literature, however their application is in direct contradiction with the evolution of the built environment, for which well-ventilated open spaces are fast becoming the norm in modern architecture. Large-scale tests conducted since the 1980s and close inspection of large open-floor plan compartment fires have shown that large compartments may not exhibit a fully-developed fire mode, but rather they may burn locally and move across the floor plate at certain spread rates, idealised as travelling fires. Numerous approaches have been proposed to characterise these types of fires, however recent experimental work has demonstrated that fire mode behaviours in large compartments may not be mutually exclusive, and is related to the characteristics of the fuel, ventilation, and boundary conditions of a compartment. This presentation showcases recent experimental work carried out by The University of Queensland and its partners in large open-floor plan compartment fires, with the results highlighting that careful consideration of the context behind a design fire must be undertaken.