Punching shear strength of reinforced concrete flat slabs subjected to fire on their tension sides
Punching shear strength of reinforced concrete flat slabs subjected to fire on their tension sides
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DOI：
10.1016/j.hbrcj.2011.10.001
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发表时间：
2012-04
期刊：
影响因子：
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通讯作者：
H. Salem;Heba M. Issa;H. Gheith;A. Farahat
中科院分区：
文献类型：
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作者：
H. Salem;Heba M. Issa;H. Gheith;A. Farahat
通过实验研究了火灾对平板冲切强度的影响。进行了一项实验计划，其中包括十四个三分之一比例的样本，其张力侧预先暴露在火中，并在同心冲孔下进行测试。主要研究参数是暴露在火中的持续时间、混凝土保护层和冷却方法。样本分别受到直接火焰 1.0、2.0 和 3.0 小时。 25 毫米和 10 毫米的混凝土盖用于测试样本。采用两种冷却方式；在空气中逐渐冷却，然后直接向板坯的加热表面喷水进行突然冷却。结果发现，板坯暴露在火中后，开裂载荷和极限冲切载荷分别降低了 18.3% 和 43%。事实证明，混凝土保护层对受拉钢筋的温度水平有显着影响。与暴露在火中 1 小时的样本相比，暴露在火中 3 小时的样本的冲切强度降低了 14%。研究发现，与逐渐冷却的样品相比，突然冷却会使冲裁强度降低 25%。提出了一种计算火灾对冲孔能力影响的简化力学模型，并发现与实验结果非常吻合。
The effect of fire on punching strength of flat slabs is experimentally investigated. An experimental program, consisting of fourteen one-third scale specimens pre-exposed to fire on their tension side and tested under concentric punching, is carried out. The main investigated parameters are the duration of exposure to fire, the concrete cover and the cooling method. Specimens are subjected to direct flame for 1.0, 2.0 and 3.0 h, respectively. Concrete covers of 25 mm and 10 mm are used for test specimens. Two cooling methods are employed; gradual cooling in air and sudden cooling with water applied directly to the heated surface of the slabs. It was found that exposure of slabs to fire resulted in a reduction of up to 18.3% and 43% in cracking loads and ultimate punching loads, respectively. Concrete cover was proven to have a significant effect on level of temperature in tension reinforcement. A reduction in punching strength of up to 14% was observed for specimens with 3 h exposure to fire compared to those with one hour exposure. Sudden cooling was found to reduce punching strength by 25% compared to specimens gradually cooled. A simplified mechanical model for calculating fire effect on punching capacity is proposed and found to be in good agreement with the experimental results.