火灾下钢筋混凝土梁热力学性能数值模拟分析*

为了研究火灾下钢筋混凝土（RC）简支梁的热力学性能，建立火灾高温下RC梁的数值分析模型，与火灾试验对比验证模型的有效性；分别对4根完全相同的RC梁进行不同受火试验，研究受火时间、混凝土高温爆裂及钢筋-混凝土黏结高温退化对RC梁截面温度场分布、钢筋应力与滑移量分布、残余抗弯承载力的影响规律。研究结果表明:截面温度梯度随受火时间增长而扩大，底部角筋比其他纵筋升温均快；混凝土爆裂对直接受火面10 mm厚度范围内温度影响较为显著，角筋升温速率随受火时间增长而增大；底部纵筋应力随受火时间增长而下降，中筋的应力高于角筋；钢混界面滑移量随受火时间增长而增大，底部中筋的滑移量小于角筋；残余抗弯承载力随受火时间增长而线性减小；爆裂深度对残余抗弯承载力的影响程度要高于爆裂面积，跨中1/5跨长位置爆裂对残余抗弯承载力影响最大。

Numerical simulation analysis on thermodynamic properties of reinforced concrete beams under fire

In order to study the thermodynamic properties of reinforced concrete (RC) simply supported beams under fire,a numerical analysis model of RC beams under high temperature of fire was established and compared with fire tests to verify the effectiveness of the model.Four identical RC beams were subjected to different fire tests to investigate the influence of fire duration,concrete high-temperature bursting and steel-concrete bond high-temperature degradation on the temperature field distribution,reinforcement stress and slip amount distribution,and residual flexural bearing capacity of RC beam sections.The results showed that the temperature gradient of the section increased with the increase of fire duration,and the temperature rise of bottom corner tendons was faster than those of the other longitudinal tendons.The concrete bursting had significant effect on the temperature within 10 mm thickness range of the direct fire surface,and the heating rate of corner tendons increased with the increase of fire duration.The stress of the bottom longitudinal tendons decreased with the increase of fire duration,and the stress of the middle tendons was higher than that of corner tendons.The slip amount of the steel-concrete interface increased with the increase of fire duration ,and the slip amount of the bottom middle tendons was smaller than that of the corner tendons.The residual flexural bearing capacity decreased linearly with the increase of fire duration.The influence of bursting depth on the residual flexural bearing capacity was greater than that of bursting area,and the influence of bursting on the residual flexural bearing capacity was the greatest at the mid-span 1/5 span length location.