【摘要】 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。更多还原

【Abstract】 Some limits exist when using the existing temperature rise curves(TRCs)of fire-resistance tests to simulate the fire scenarios in subway sectional tunnels.Herein,the improved RABT(IRABT)TRC model is proposed in this paper.Based on the existing TRCs of fire-resistance tests,the model considers such practical factors,as the peak temperature,the fire duration and the heating rate of the fires in subway sectional tunnels.The linear cooling segment is included in the model;the cooling time can also be set to characterize the practical fire scenario.The finite element software SAFIR,specifically for structural fire-resistance analysis,is used to numerically simulate the fire-resistance tests of a 1/3reduced scale subway tunnel segment with IRABT TRCs.The temperature variation and the sectional temperature field distribution,with five different fire scenarios,are obtained,corresponding to such IRABT models as the ones with the cooling moment 60 min and the peak temperature of 700℃and 800℃,respectively;and the ones with the cooling moments 60,45 and 30min,respectively,and the peak temperature of 900 ℃.Numerical simulation results show that the temperature of the section of 20 mm above the heating surface continues rising,and the farther the distance to the heating surface,the longer the temperature rise will last.In addition,as for the section of 90 mm above the heating surface to the top of the segment,no obvious cooling segment occurs,and temperature rise and constant remaining reveals all the same.Moreover,the temperature of the heating surface is lower than that of the adjoining sections within the segment lining;meanwhile,the peak value of the temperature field of the whole segment lining appears at the range of 40 to 60mm above the heating surface.As for the cases with the same temperature rise segment,the later the cooling moment,the higher the final temperature,near the heating surface and the top,will be.Therefore,for the practical fire scenario in subway sectional tunnels,the fire is better to be effectively controlled at the early stage,so as to avoid entering the constant-temperature heat-transfer condition,alleviating the damage degree of the segment concrete caused by heating.The analysis results may provide insight into the performance degradation of the segment linings of subway tunnels under fire.更多还原