火灾下矩形钢筋混凝土梁柱温度场的CA模拟

Cellular Automata Simulation of Temperature Field of Reinforced Concrete Beam and Column Under Fire

建筑物遭受火灾高温作用时构件的承载力、耐久性会受到不同程度的损伤,使整个建筑结构的安全性降低。确定火灾下混凝土结构的温度场分布是进行火灾下力学性能分析的前提,而混凝土结构温度场一般不受其内力和变形状态影响,因此温度场分析可以先于结构分析独立进行。本文基于元胞自动机(Cellular Automata,CA)原理建立了火灾下钢筋混凝土热扩散的CA模型,并通过CA模型复原了传热过程。使用CA模型计算分析了失火混凝土梁柱试件三面受火的情况下横截面内温度分布场,并和现有试验结果进行了比较,两者吻合度较好,证实了CA模型在火灾下钢筋混凝土中温度场分析的可行性和有效性。运用CA模型对不同受火方式下的矩形钢筋混凝土梁柱温度场进行分析,得到钢筋混凝土梁柱截面内的温度损伤与受火方式及受火时间密切相关。四面受火时,温度损伤最为严重,且靠受火面越近升温速度越快。

When a building is subjected to fire and high temperature, the bearing capacity and durability of its components will be damaged in different degrees,decreasing the reliability of the whole building structure.Determining the temperature field in concrete structures under fire is a prerequisite for analyzing their mechanical properties.Since the temperature field in concrete structures has nothing with their internal force and deformation state, the temperature field analysis could be performed prior to mechanical analysis.According the Cellular Automata（CA） method,a CA model for thermal diffusion of reinforced concrete under fire was established.The heat transfer process was reproduced by the CA model.Furthermore, the proposed CA model was used to study the distribution of temperature field in the crosssection of concrete beam specimen whose three sides were heated under fire.Comparison of the CA numerical solutions with the existing experimental results shows that they agree very well, implying that the present CA model is feasible and effective in analyzing the temperature field in reinforced concrete structures under fire.Finally, the proposed CA model was further employed to examine the temperature field of rectangular concrete beam and column under different fire exposure. Results show that the cross sectional temperature damage of the beam and column associates with the fire exposure mode and time.When the concrete beam and column is surrounded by fire, its cross sectional temperature damage is the most serious.The closer the beam side is from fire, the faster the temperature rises.