Comparative experimental study on factors affecting fire spread in enclosed buildings
To observe the fire spread spatiotemporal evolution within enclosed buildings and explore the fire spread process,a two-storey 2x2 moment-resisting steel framed structure was constructed.Four rooms were arranged on the first floor,and wood cribs were employed as the fire load.Four distinct scenarios were considered based on fire load,compartment elements and opening size.During the experiment,the fire spread process was observed by the camera,the gas-phase temperature field was recorded by thermocouples,and the heat release rate was measured based on oxygen-consumption method.The experiment reveals that the pre-flashover stage during the fire process has a significantly prolonged duration,accounting for 70％-85％of the total fire spread time.The fire rapidly intensifies in the post-flashover stage and propagates to adjacent rooms within a short timeframe.The heat release rate at fire spread stage is approximately 1.5 to 4 times that at the flashover stage.The findings indicates that the spread of fire in confined space buildings manifests itself as a transition from an uneven temperature field to a uniform temperature field in space,and as a gradual increase in the fire spread rate in time.Before the fire spreads,the temperature field of the target compartment is reduced to a certain extent compared to the temperature field of the fire room.Local fire load density and total fire load exhibit positive influences on enclosed fire spread.Opening size influences smoke propagation between compartments,and compartment elements barriers hinder smoke flow and flame propagation,which significantly affects the fire spread process.
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