钢筋混凝土矩形梁的当量耐火时间

T-equivalent used to assess the fire resistance of RC rectangular beam

为了正确评估钢筋混凝土矩形梁在实际火灾条件下的承载力,以一般室内火灾轰燃后的房间平均温度-时间曲线为火作用,以热传导和建筑结构耐火理论为基础,以梁在实际和标准火灾下的承载力相等为等效准则,用数值计算方法研究梁的当量耐火时间,并用最小二乘法导出其计算公式。火灾房间火灾荷载越大,开口因子越小,梁的当量耐火时间越长;反之越短。所给梁的当量耐火时间可用于建筑结构性能化耐火设计与评估:当火灾荷载密度较大,开口因子较小时加大梁的截面参数以获得安全性,反之,减小截面参数以获得经济性。

In order to evaluate the fire resistance of RC beam exposed to the fire in a compartment, the equivalent fire-resistance time of the beam is studied by numerical analysis, based on the theory of unsteady heat transfer, in terms of the principle that the RC beam exposed to the post-flashover fire of a compartment and standard fire has equal bearing capacity. The equivalent fire-resistance time regression formula is fitted. The result illustrates that higher fire load or smaller ventilation factor in a compartment would achieve longer equivalent fire-resistance time of the RC beam. The regression formula given in this paper can be applied to fire resistance design and evaluation of the RC beam： if with higher fire load or smaller ventilation factor, bigger cross-section beam should be adopted to acquire safety; otherwise, smaller cross-section beam can be adopted.