Time-dependent variation distribution of fire temperature for concrete hollow thin-walled pier affected by flame fluid
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摘要: 针对火灾场气流与焰域温度空间耦合变化时的结构响应, 通过考虑气流流速及焰围空间和结构物高度的相互作用效应, 建立了焰流场环境火灾模型。采用时间增量迭代的方法计算了焰流场温度, 研究了复合边界控制方程和对流换热与流速之间的相互关系。分析了流场中结构迎流面和侧流面温度分布状态, 研究了混凝土空心薄壁墩的环境火灾场景, 建立了焰流场结构耦合模型, 揭示了焰流效应下混凝土空心薄壁墩三维空间火温时变分布规律。研究结果表明: 火延时间为120min, 流速为3m·s-1时, 近火点温度比其他流速下温度约高100℃, 流速对火源温度呈非线性影响状态; 500℃以上的高温层在混凝土空心薄壁墩迎火面分布深度仅为7cm, 在竖向荷载作用下空心薄壁墩外层迎火面混凝土易产生层剥现象; 迎流面温度远高于侧流面温度, 背火面温度无变化; 稳态低流速场中流速的变化可改变不同温度区域的分布, 并扩大迎火面高温区面积。Abstract: For the structure response of the coupled variation of air current in fire field and flame temperature space, considering the effect of air current speed as well as the interaction effect of flame space and structure height, the surrounding fire model in flame fluid field was created. The temperature of flame fluid field was calculated by using time increment iteration method. The comprehensive boundary control equation and the relation between convection heat exchange and air current speed were studied. The temperature distribution statuses of facing-fluid side and lateral-fluid side in fluid field were analyzed, the surrounding fire scene of concrete hollow thinwalled pier was studied, the coupled model of flame fluid field was proposed, the time-dependent variation distribution law of fire temperature for concrete hollow thin-walled pier affected by flame fluid was revealed. Analysis result indicates that when fire time is 120 min and air current speed is 3 m·s-1, the temperature near fire source is about 100℃ higher than that at other air current speeds, the influence of air current speed on fire source temperature is nonlinear. Thedistribution depth of high temperature layer (higher than 500℃) on facing-fire side is only 7 cm, the outer facing-fire side concrete of hollow thin-walled pier strips easily under vertical load. Temperature on facing-fluid side is much higher than temperature on lateral-fluid side, temperature on far side of fire does not change. The distribution domains of different temperatures can be changed with the variation of air current speed in steady low fluid field, and the high temperature area on facing-fire side can be enlarged.
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图 2 混凝土空心薄壁墩环境火灾场景
Figure 2. Surrounding fire scene of concrete hollow thin-walled pier
图 3 混凝土空心薄壁墩截面尺寸及钢筋构造
Figure 3. Section dimension and steel constitution of concrete hollow thin-walled pier
图 6 各测点温度时变分布
Figure 6. Temperature time-dependent variation distributions at measuring points
图 7 不同流速下温度时变分布
Figure 7. Temperature time-dependent variation distributions at different fluid speeds
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