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Fire performance of steel portal frame buildings
Published in Peter J. Moss, Rajesh P. Dhakal, Progress in Mechanics of Structures and Materials, 2020
M.W. Bong, A.H. Buchanan, R.P. Dhakal, P.J. Moss
The fire curve used in most of the analyses in this study was the ISO 834 Standard Fire [ISO 1975]. However, the ISO fire is intended to represent fires in small compartments. The behaviour of a fire in a large compartment, such as warehouses or industrial buildings, is not the same as a small enclosure fire. These buildings usually have very high ceilings and large open spaces. The fire plume will have entrained a large amount of cold air when it impinges on the ceiling. The hot gases will continue to spread across the ceiling and similarly, cold air will be entrained into the ceiling jet. Therefore, the radiant heat flux from the upper hot layer may not be high enough to cause flashover. For this reason, the Eurocode External fire [EC1, 1994] (Figure 4) was used for some analyses [Bong 2005],
Ignition
Published in James G. Quintiere, Principles of FIRE BEHAVIOR, 2016
when the incident heat flux is greater than the CHF. Example 4.1Let us consider a typical material that might represent a drapery or a thin fabric on an insulating substrate, similar to a cushion or upholstered product. Representative properties for a cotton-like material are ρ = 0.57 g/cm3, c = 0.34 cal/g-K, and l = 1 mm. For Tig = 300°C, ignition times range from 5 to 25 seconds for a range of radiant heat fluxes between 40 and 10 kW/m2, respectively. For Tig = 400°C, these times only increase by about 25%. For this reason, these objects can ignite very quickly regardless of their precise ignition temperature. The heat capacity factor, ρcl, controls the process.Flashover conditions are sometimes designated with a heat flux to the floor of 20 kW/m2 (indicative of room smoke layer temperature of 500°C–600°C). So, we see that most thin materials will rapidly ignite under this condition, consistent with our concept of flashover causing the fire to suddenly grow.
Performance-based design and risk assessment
Published in Andrew Buchanan, Birgit Östman, Fire Safe Use of Wood in Buildings, 2023
Paul England, David Barber, Daniel Brandon, Christian Dagenais, Gianluca De Sanctis, Michael Klippel, Dennis Pau, Colleen Wade
Figure 11.4 shows a generic graph of enclosure temperatures versus time for a small fire enclosure, together with potential fire behaviour and interventions that may modify the fire. The top (solid) line in this graph shows a fire scenario where the fire reaches flashover and passes through a decay phase. The dotted line shows a cooling phase assuming no re-growth, secondary flashover or extended periods of smouldering combustion occurring. The dashed lines show various interventions that can reduce the severity of a fire.
Fight or flight? Behaviour and experiences of laypersons in the face of an incipient fire
Published in Ergonomics, 2021
Meinald T. Thielsch, Julia Kirsch, Hannah Thölking, Lena Tangelder, Christoph Lamers
In the flashover, an incipient fire can suddenly develop into a full fire and thus endanger additional, previously uninvolved persons as well as rescue teams and can immensely increase material damage. Depending on the fire load and ventilation, the time of the flashover is often between 2 and 12 minutes (Kunkelmann and Brein 2010). In modern apartments, flashovers and lethal concentrations of fire gases can occur in under 3–5 minutes (Kerber 2012; Kunkelmann 2003). Since a flashover will most likely happen before the fire brigade arrives, it is all the more important that the person who discovers the fire reacts quickly and prevents the fire from spreading. Clearly, the time span between the emergence of the fire and the arrival of the fire brigade is enormously relevant for the lives and health of the people affected and the rescue teams.