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既有耐火试验标准升温曲线用于模拟地铁区间隧道火灾场景存在局限性。提出了改进RABT(IRABT)标准升温曲线模型,该模型基于既有耐火试验标准升温曲线,同时考虑了地铁区间隧道火灾的峰值温度、受火持时与升温速率等特征,且包含线性降温段,可设置降温时点,以描述实际火灾场景。采用结构抗火有限元分析软件SAFIR,对1/3缩尺地铁隧道管片的耐火试验进行了IRABT标准升温曲线下的数值模拟,获得了5种不同火灾工况下管片温度变化及截面温度场分布,所对应的IRABT模型分别为:峰值温度700℃与800℃,降温时刻为60min;峰值温度900℃,降温时刻分别为60、45、30min。模拟结果表明,进入降温阶段后,管片受火面20mm以上区域,温升仍将持续,且距离受火面越远,温升持续时间越长;距离受火面90mm以上至管片顶部,已没有明显降温段出现,该区域始终保持升温趋稳状态。降温开始30min后,受火面温度开始低于紧邻的管片内温度;受火试验结束的180min时刻,整个管片内部温度场峰值出现在距受火面40~60mm范围内。同一升温曲线降温时点越迟,则管片近受火面及顶面区域的最终温度越高。因此,对于实际地铁区间隧道火灾,应尽量在升温初期对火势加以有效控制,避免进入恒温传热阶段,可减轻管片混凝土传热破坏程度。该分析结果可为研究地铁隧道衬砌结构受火性能退化提供参考。
Existing fire test standard temperature curve used to simulate metro tunnel fire scene limitations. This paper proposes an improved RABT (IRABT) standard temperature rising curve model. The model is based on the existing temperature rise curve of the fire resistance test, taking into account the peak temperature, the fire holding time and the heating rate of the subway tunnel fire zone, including the linear cooling zone, You can set the cooling point to describe the actual fire scene. The structural fire resistance finite element analysis software SAFIR was used to simulate the fire resistance test of 1/3-scale subway tunnel segment under the IRABT standard temperature rise curve. The temperature change and cross-sectional temperature of the segment under 5 different fire conditions Field distribution, the corresponding IRABT models are: the peak temperature of 700 ℃ and 800 ℃, the cooling time is 60min; the peak temperature of 900 ℃, the cooling time were 60,45,30 min. The simulation results show that, after entering the cooling stage, the segment will continue to heat up more than 20mm, and the longer the distance from the fire face, the longer the duration of temperature rise. The distance from the fire face to 90mm above the top of the segment, No obvious cooling section has appeared, the region has maintained a steady warming state. 30 min after the start of cooling, the temperature of the fire surface started to be lower than the temperature of the adjacent pipe; at 180 minutes after the end of the fire test, the peak of the temperature field in the entire pipe appeared within 40-60 mm from the fire surface. The later the time when the same temperature curve is lowered, the final temperature of the segment near the fire and top surface will be higher. Therefore, for the actual subway tunnel fire, it should try its best to control the fire in the early stage of temperature rise to avoid entering the stage of constant temperature heat transfer and reduce the extent of heat transfer and destruction of the concrete. The results of the analysis can provide a reference for studying the degradation of fire performance of subway tunnel lining structure.