火灾时围护结构非稳态温度场的动态特性

为了研究火灾时建筑物围护结构的温度,运用BFD模化模型,模拟计算了室内建筑火灾烟气温度与时间的变化关系,并讨论了长宽比、有效通风口高度等对室内火灾过程的影响.在上述火灾模拟的基础上,根据烟气与围护结构之间的换热情况,建立了围护结构非稳态传热模型.采用分界面衔接条件,并结合有限差分方法,提出了一种建筑构件中心点温度场的计算方法.随后,取时间步长为1 s,计算时间为50min,分别计算了两种围护结构内部温度场随时间和位置的变化规律.计算时,火灾增长时间tg为150 s,衰减时间td为600 s,所选取的火灾为经历了生长阶段、轰然阶段、充分发展阶段和衰减阶段的全过程燃烧.模拟得到的加气混凝土和钢筋混凝土构件内部温度场变化规律与实验结果基本符合.

Dynamic Characteristics of Unsteady Temperature Field of Frame Structure Exposed to Fire

In order to investigate the temperature of the frame structure exposed to fire,the variation of smoke temperature in the compartment with time is simulated via the Cardington large scale modeling experimental model(BFD),and the effects of the height/width ratio and the effective opening width on the fire process are analyzed.Based on the simulated results,a model describing the unsteady heat transfer of frame structure is then established according to the heat transfer between the smoke and the frame structure.Moreover,a method to calculate the temperature field in the building component center is proposed by means of the finite differential method as well as by considering the interface joining condition.Finally,the temperature field variations of two kinds of frame structures with the height and the time are calculated,in which the time step,the full calculation time,the fire growth coefficient tg and the fire decay coefficient td are selected respectively as 1 s,50 min,150 s and 600 s,and the fire experiences all the fire period including the growth,the flashover,the full development and the decay stages.The simulated temperature fields of the reinforced concrete and air-entrained concrete components basically accord with the experimental ones.