闭口楼承板的耐火设计
闭口楼承板的耐火设计，本文只针对闭口楼承板的防火述说，其他板型（开口楼承板，燕尾式楼承板）的防火将在以后更新；
文章关键词：楼承板耐火|组合楼板耐火|闭口楼承板|楼承板防火
防火的主要目的在于保生户生命安全同时将财产及经济损失降至最低, 这些目的基本上可以由以下的方式达到:
The aims of fire precautions are to safeguard life and to minimize fire damage to property and financial loss. These aims are principally achieved by:
(1 )将引火的风险降至最低。
(1) minimizing the risk of ignition:
(2) 提供大众安全的逃生通路及出口。
(2) providing a safe exit for occupants;
(3)限制火势的重延。
(3) restricting the spread of fire;
(4)将结构体受火燃烧后可能1明塌的风险降至最低。
(4) minimizing the risk of structural collapse.
在这里, 我们所要说明的组合楼板的耐火设计. 就是为了上述第(3)及第(4)项:
This section is concerned with items(3) and(4).
由于闭口楼承板完全密合的闭口肋断面设计,其组合楼板提供一个均匀混凝土厚度的隔火屏障,当板底遭火延烧时，除了波谷平板部分因为直接曝火. 将被视为无效用钢以外, 其余被混凝土完全裏覆的板肋，它们的温度变化就如同现浇混凝土楼板里的钢筋在不同保护层厚度下的温度变化相似, 依然是相当称职的抵抗正弯矩钢筋, 因此闭口楼承板组合楼板的面1t火设计性能(无论是隔热性、完整性以及结构性)很明显地不是其它种板型 (开口型或缩口型) 组合楼板所能媲美 。
Due to the closed rib design, the BARD composite slab provides an uniform thermal insulation. Except the flat soffit, all the ribs are covered by the concrete and are not exposed to the fire, the final temperature of the ribs will be the same result as the re-bars placed at the same depth into the concrete slab, and still acting as a competent positive reinforcement. it is obvious that BARD is much superior to any other kinds of trapezoidal and/or re-entrant profiled steel sheets in the fire resistance.
无防火披护组合楼板设计
Unprotected composite slab design
规则一:楼板最小厚度
Rule1: Minimum slab thickness
根据英国国家标准BS 5950 Part8: Section8.9对于压型钢板组合楼板在板底没有防火材料保护状况下, 楼板所必须具备的隔热最小厚度有很明确的界定, 详下表:
In accordance with BS 5950 Part8:Section8.9, the minimum slab depth of unprotected composite slabs with profiled steel sheeting for thermal insulation is clearly limited, see the following figures:
开口型(Trapezoidal Profiled)
| 耐火时效 Firerating(minutes) |
60 |
90 |
120 |
|
最少覆盖厚度(mm)
Min. cover thickness |
70 |
80 |
90 |
缩口型(Re-entrant Profiled)
| 耐火时效 Firerating(minutes) |
60 |
90 |
120 |
最少楼板总厚(mm)
Min. total slab thickness |
90 |
110 |
125 |
根据温度探测试验以及在有荷载条件下的耐火试验结果,显示闭口组合楼板的隔热性都显著优于缩口板型.因此在各种耐火极限条件下选择闭口组合楼板所需最小楼板厚度时,参考缩口型板组合楼板的有关规定即绰绰有余。
in accordance with the test result of Temperature Survey and Fire Endurance, it shows that the thermal insulating performance of BARDE composite slabs are far better than any kind of re entrant profiled deck slabs, therefore ,it is certainly sufficient to decide zhe minimum zhickness of BARD composite slabs in accordance with the guidance established for the re-entrant profiled deck slabs.
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