不同升温条件TN梁火灾行为的有限元分析

采用有限元法对H型简支钢梁在火灾下的热、结构响应进行模拟，得到了瞬态温度场分布，挠度、轴向变形随温度变化的曲线，构件的耐火时间和耐火温度以及屈曲破坏形态，并与试验结果进行了比较；分析了不同升温条件下钢梁的温度场分布和变形规律；研究了升温速率对钢梁火灾性能的影响。结果表明：火灾升温速率不同时，梁截面呈现出不同的非线性温度梯度；升温速率小，截面温度梯度小，耐火时间长，梁变形主要为热膨胀；升温速率大，环境温度高，截面温差大，耐火温度高，屈曲破坏时能承受的挠度也大，但耐火时间短，梁变形为热膨胀和热弯曲的组合。

Finite Element Analysis of Fire Behavior of Steel Beam under Different Elevated Temperature Conditions

The finite element method is applied to simulate thermal and structural coupling responses of H section simple supported steel beam in fire. The transient temperature distribution, the curves of deflection and axial deformation with temperature, fire resistant duration and temperature, buckling damage mode are obtained. The results by numerical simulation are compared with those from experiment. The temperature distributions and deformation regulations under different elevated temperature conditions are analyzed. The effect of temperature rise rate on fire behaviors of beam is studied. It is found that the cross section of the beam shows different non-linear temperature gradients when with different temperature rise rates in fire. With lower temperature rise rate, the beam has a small section temperature gradient and longer fire-resistant duration. The deformation of beam primarily results from thermal expansion. On the other hand, when temperature rise rate and ambient temperature are higher, the beam has a larger temperature difference, higher fire-resistant temperature and shorter fire-resistant duration. The beam can undergo a large deflection before buckling damaged. The deformation results from combination of thermal expansion and bowing.