火灾下匀质防火保护钢构件温度计算(II)：实际火灾环境计算

目前各国规范给出的计算火灾下有匀质防火保护的钢构件温度的公式都是基于标准火灾环境得到。标准火灾只包含升温段而实际火灾包括升温段和降温段。考察了将现有公式用于实际火灾环境计算的有效性。通过工况分析,考察了不同火灾、不同厚度、不同截面和不同防火涂料情形下的钢材温度。通过与有限元分析的结果比较,我国规范推荐的公式给出的钢材温度与有限元结果符合最好。研究同时表明欧洲规范中使用的避免升温早期负钢材温度增量的方法,即升温段当计算得到的钢材温度为负值时取增量为0,会引起最高钢材温度和降温段钢材温度的偏高,不适用于实际火灾环境计算。综合而言,我国规范最适用于实际火灾环境计算。

Temperature calculation of uniformly insulated steel members in fire (II): use in real fires

The formulae recommended by codes in different countries are originally derived in the standard fire which only in- eludes heating phases, however, real fires have both heating and cooling phases. This paper investigates the applicability of the current formulae for calculation in real fires. Case studies are conducted to investigate the parameters for different real fires, different insulation thicknesses, different sections and different fire proofing materials. Comparing with FEM results, the for- mulae recommended in Chinese code give good predictions. The study also shows that the treatment adopted by eurocode to a- void negative steel temperature increment in early heating phase, for which if the calculated steel temperature increment is nega tive then the increment is taken as zero, is not suitable for real fires, because it will lead to over-predictions of the maximum steel temperature and steel temperatures in cooling phases. Overall, the formulae given in Chinese code are recommended for calculation in real fires.