Steel Buildings in Europe

Part 6: Fire Engineering 6 - 28 in Figure 4.3. The severity of a fully developed fire is governed by the ventilation condition and quantity and nature of the fuel within the compartment. Standard Fire Parametric fire 0 200 400 600 800 1000 1200 0 30 60 90 120 150 180 Time (min) Gas Temperature (°C) Figure 4.3 Model of fully developed fire 4.1.4 Nominal temperature-time curve Standard fire EN 1991-1-2, §3.2 uses the standard temperature-time curve to represent the thermal action of a fully developed fire. This ‘standard fire’ is used to classify the fire performance of the structural materials and members in standard fire furnace tests. It forms the basis on which the fire resistance time and load bearing resistance of structural members are evaluated using the simple calculation models from EN 1993-1-2 and EN 1994-1-2. It is also used in the performance-based analysis for fire design of a whole structure. 4.1.5 Natural fire model Parametric fire EN 1991-1-2, Annex A defines a parametric temperature-time curve for fire compartments up to 500 m 2 floor area. This ‘parametric fire’ consists of a heating, cooling and residual phases. The heating phase is normally represented using an exponential curve up to a maximum temperature. The cooling phase is described by a sloping straight line until it reaches the residual phase. For a parametric fire, the heating phase depends on ventilation conditions and the thermal properties of the compartment boundary. The heating duration and maximum temperature are governed by the density of the fire loads and the ventilation condition. The cooling phase is controlled by the heating duration and the maximum temperature that has been reached. To some extent, the parametric fire represents the characteristics of a natural fire. However, its accuracy for estimating the thermal response of fire depends on the accuracy of the input data, such as fire load, ventilation condition, compartment size and thermal properties of the boundary condition.