大空间火灾下铝合金构件温升计算方法

Calculation method for temperature rise of aluminum alloy structural members in large-space fires

性能化抗火设计过程中,火灾下结构构件的温升计算方法对设计结果具有重大影响。为研究大空间火灾下铝合金构件的温升计算方法及火焰辐射对构件温升的影响,对2种常见的铝合金构件截面试件进行了火灾温升试验。试验结果表明,由于火焰辐射的作用,构件温度与周围空气温度较为接近。基于铝合金构件的导热微分方程,提出了一般室内火灾和大空间火灾下铝合金构件的温升计算方法,并与试验结果进行了对比分析。结果表明:计算大空间火灾下铝合金构件温升时,忽略火焰辐射的作用会导致结果偏于不安全;所提出的基于点火源假定的火焰辐射热量计算方法较欧洲规范中的计算方法更为简单准确。此外,火焰辐射下烟气黑度值对构件温升的计算具有较大影响,并根据试验结果拟合了烟气黑度的实用计算式,计算结果与试验拟合结果吻合良好。

In the process of performance-based fire design, the calculation method for the temperature rise of structural members in fire has a significant influence on the design results. In order to study the calculation method for the temperature rise of aluminum alloy structural members in large-space fires, as well as the influence of the flame radiation on the temperature rise, two aluminum alloy specimens with commonly used sections were tested in fire. The experimental results show that the temperature of the specimens is close to that of the surrounding air due to the fire radiation. Based on the heat transfer differential equation of aluminum alloy structural members, the calculation methods for the temperature rise of aluminum alloy members under compartment fires and large-space fires were proposed and compared with the experimental results. The analysis results show that the ignorance of the effect of fire radiation on the calculation of temperature rise of aluminum alloy members in large-space fires will lead to unconservative results. The proposed method based on point fire assumption for calculating the radiative heat flux of the fire is more accurate and simpler than the method recommended by Eurocode. In addition, the emissivity of smoke under the fire radiation has great influence on the calculation of the temperature rise of members. A practical formula was fitted based on the experimental results.The results of the formula agree well with the experimental results.