fire safety engineering SWEDEN Possibility to reduce structural fire resistance with a sprinkler system by applying a reduced fire load (qfd) of 60% of the original value.
UNITED STATES The structural fire resistance remains unchanged and must comply with the national codes even if sprinkler systems are mandatory.
UNITED KINGDOM Possibility to reduce the class of fire resistance if sprinklers are present and only in buildings lower than 30m; ITALY
Possibility to reduce the class of fire resistance if sprinklers are present together with openings for smoke and heat clearance purposes. SWITZERLAND
Possibility to analyse the structural fire resistance with a performance-based approach with a simplified empirical HRR curve with a lowered peak when in presence of a sprinkler system.
Possibility to halve the class of structural fire resistance if sprinklers are present; FRANCE The structural fire resistance remains unchanged and aligned with the national codes even when the building is provided with a sprinkler system.
applied to the structures as well as the overall amount of smoke produced by the fire, therefore impacting the correct sizing of additional active protection systems. At the same time, it should be noted that this approach is profoundly different from that adopted by other European countries. One clear example is shown within the Eurocodes. Within the Eurocode 1 part 1-2, the additional specific information paragraph specifies that a full analytical procedure for structural fire design would take into account the behaviour of the structural system at elevated temperatures, the potential heat exposure and the beneficial effects of active and passive fire protection systems, together with all the uncertainties associated this process. Hence, the procedure also includes an analysis of the uncertainties and the possible consequential effects on structures (e.g. potential structural failure). A correct analysis also requires the designer to consider the case in which one or more of the passive and / or active protection measures may fail, such as an inactive sprinkler system or a fire door stuck in the open position. This worst-case scenario is totally neglected by the Italian Code. This study compares the approaches of other countries and highlights the importance of the “uncertainties” when totally neglected. According to the building code ruling in Switzerland (AICAA 2015), sprinkler systems can be taken into consideration for the determination of the fire resistance of the load-bearing structures, such as the walls and slabs, as well as increasing the maximum size of the allowed fire compartment. At the same time, the mere presence of a fire control system allows the fire engineer to halve the class of the fire resistance of the designed structure. Additionally, within the Swiss legislation, the designer can address the structural fire design through a performance-based approach. In this instance, the designer is required to define and agree with the relevant authorities the fire scenarios that will be used in the evaluation of the structural response in case of fire. The study must also consider the unavailability of one of the active protection systems, if applicable, and therefore evaluate all the possible consequences.
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outlook
Possibility to analyse the structural fire resistance with a performance-based approach with an empirical HRR curve without the activation of sprinklers.
Two fire codes used in the United Kingdom (BS9991 and BS9999) allow the designer to reduce structural fire resistance in buildings lower than 30 m if a sprinkler system is installed to EN12845. In residential buildings, BS9991 gives the opportunity to assess the resistance of structural elements based on the number of openings towards the exterior within the analysed compartment. This method takes into account the heat generated by the fire and exhausted towards the outside of the building. The Swedish fire prevention code (BFS 2018:4) allows the fire engineer to reduce the fire load to 60% of its original value when the building is fitted with a sprinkler system. However, unavailability of the system is not considered. In France, the presence of an active fire protection system does not permit any relaxation in the fire resistance of structural members, which must comply with the requirements and methods imposed by the national code (ERP R-123 and EN 13501-2). Similarly, in the USA (IBC: 2018), the presence of a fire protection system does not allow any downgrade in the fire resistance of structural elements.
Figure 1 - HRR curve with and without sprinkler activation
