中文摘要：

在合理考虑混凝土热工参数的基础上，根据三面受火下带保护层钢筋混凝土梁离散体积单元的热平衡原理建立有限差分平衡方程，采用有限差分法导出了任一体积单元的温度计算公式，编制了截面温度场非线性有限差分程序，通过算例分析，验证了程序的正确性，对带保护层钢筋混凝土梁的温度场分析表明，采用保护层能有效的提高钢筋混凝土梁的耐火极限。这为进一步深入研究火灾下带保护层钢筋混凝土梁的力学性能和耐火极限创造了条件。

英文摘要：

Considering the thermal properties of concrete, the finite difference equation was built and formula for the temperature field of each element was deduced by using elemental heat energy balance of reinforced concrete beam with safeguard under three side exposing to fire. The program was developed for the nonlinear finite difference analysis of the temperature field within reinforced concrete beam with three side exposing to fire, an example of calculation was conducted and the program was validated by the experimental results from references, the analysis of reinforced concrete with safeguard indicates that it will enhance the limit of reinforced concrete against fire with safeguard. It is possible for further researches on the behaviors and fire resistance of reinforced concrete beam with safeguard.