基于升降温全曲线的钢筋混凝土梁温度场分析

摘要

文章基于 ISO834标准升降温全曲线，运用 ABAQUS 非线性有限元分析软件，以钢筋混凝土矩形截面梁为例，进行了单面、三面及四面受火工况下的梁截面温度场分析，得出了梁截面不同观测点的温度随标准升降温全曲线的变化规律。结果表明：由于混凝土的热惰性，越靠近受火面温度变化梯度越显著，除直接受火的截面边界之外，截面内部的升温出现不同程度的滞后现象，离受火面距离越远，滞后时间越长；钢筋混凝土梁经历升降温全过程后，梁截面各点经历的升温峰值温度不同，达到升温温度峰值的时间也不同，越远离受火面越滞后；在受火面停止升温进入降温阶段时，截面内部可能还处在升温阶段，形成了钢筋混凝土梁在受火面升温时其外部受火面温度高于截面内部温度，而在受火面停止升温进入降温段时，截面内部温度存在高于外部温度的情况，此现象在分析受火灾作用钢筋混凝土梁的承载性能时应加以考虑。%The paper studies the change rule of temperature field of reinforced concrete structures in the process of rise and cooling temperature under high temperature which is of great significance to understand its when subjected to fire resistance. In this paper,based on standard ISO834 heating and cooling curve,using the nonlinear finite element analysis software ABAQUS,with reinforced concrete rectangular section beam as an example,the beam cross section temperature field analysis on single side,three sides and four sides fire conditions has been carried out,and the whole temperature to time curve of the different observation points in beam section is obtained. The analysis results show that due to the thermal inertia of concrete,more close to the fire side of beam section,the temperature gradient is more significant. In addition to direct fire section boundary,the cross section of internal temperature appears different degree of hysteresis,the farther from the fire surface distance,the longer the time lag. After Heating and cooling process,in the beam section,the peak temperature of warming experience are different at various observation points and the time to reach the peak temperature are different too,and the more far away from the fire surface,the more lagging. When beam surface stopping heating and into the cooling stage,Cross section internal observation point may still in the phase of heating,so when beam external surface warming the internal temperature of the surface is higher than the external surface,and when beam surface stopping heating and into the cooling stage,the temperature of the internal cross section are higher than that of beam surface.