火灾下匀质防火保护钢构件温度计算(Ⅰ):理论与公式

Temperature calculation of uniformly insulated steel members in fire(Ⅰ): theory and formulae

介绍了火灾下有匀质防火层保护的钢构件温度计算的一维传热模型。给出了求解该模型的相关边界条件和假定,并给出求解该一维传热模型在不同边界条件下的解。通过分析三种典型防火材料保护下、截面系数不同的三种截面的升温,比较了由我国规范CECS200、欧洲规范、欧钢协标准、美国规范及其他学者推荐的方法得到的结果,并对照有限元结果,考察了不同计算方法的有效性。结果表明,CECS200与国外规范给出的结果符合良好且略微偏高。通过计算典型截面在不同耐火极限要求下的最小保护层厚度,比较了各国规范的设计结果。结果显示,由不同规范推荐的公式计算得到的最小保护层厚度相差不大。CECS200计算的最小保护层厚度与国外规范一致,与欧洲规范得到的结果基本相同。研究表明,在标准火灾环境中我国规范给出的方法合理有效且形式简单便于工程运用。

One-dimensional heat transfer model for calculating the temperature of uniformly insulated steel members in fire is in- troduced. The solutions of the model by different approaches with different boundary conditions and assumptions are giverL The temperatures of three steel sections insulated by three typical fire proofing materials are investigated. The results of steel temperatures calculated by different formulae given in different codes which include Chinese code CECS200, Eurocode, Europe- an Steel Committee, American code and others, are compared with the numerical results predicted by FEM. Comparing with other codes, CECS200 gives consistent and slightly conservative results. The minimum fire proteclion thickness of three type steel sections under different fire resistance ratings are determined by different codes. Different codes give consistent results. Results given by CECS200 agree well with those by other codes, and fit perfectly well with resul：s given by Eurocode. The study shows that the formula given by Chinese code can give acceptable results in standard fire calculations, and the formula is given in a simple form which is convenient for practical usage.