火灾作用下钢结构外伸式端板连接节点的热应力

Thermal stress of overhang type end plate connection nodes of steel structure in fire

为了研究钢结构在火灾中形成的热应力对节点受力性能的影响,以及热应力与总应力的比重关系,采用有限元软件ABAQUS对外伸式端板连接节点有限元模型进行温度场和热-力耦合模拟,得出热应力变形图和热-力耦合Mises应力云图,分析得出火灾中热应力占总应力的比重,以及火灾中钢节点跨中挠度的变化关系。结果表明:火灾作用下外伸式端板钢节点处热应力占总应力比重高达0.92以上,极大地削弱了结构在高温下的受力性能,此时钢节点破坏主因是热应力过大。火灾中框架的跨中挠度急剧增大,且在火灾持续到80 min时由于挠度过大而失效;常温模拟中钢梁却未发生失效,说明高温对钢结构受力极为不利。

This paper is an effort to investigate the effect on the node force performance by the thermal stress found in steel structure exposed to the fire disaster,together with the proportion between thermal stress and total stress. The study consists of simulating the temperature field and thermal-mechanical coupling of overhang type end plate connection nodes using the finite element software ABAQUS; working out the thermal stress deformation figure and the thermal-mechanical coupling Mises stress nephogram;analyzing the thermal stress accounted for the proportion of total stress in the fire; and changing the relationship between the deflection of steel nodes in the fire,The results show that the thermal stress of overhanging end plate steel node in the fire accounts for more than 0. 92 of total stress,greatly weakening the mechanical properties of the structure in high temperatures,in which case the main contributor to the steel node failure is excessive thermal stress. The midspan deflection in framework increases sharply in the fire until it fails due to the excessive deflection resulting from 80 min fire. But no failure occurs at normal temperature,showing that high temperature is extremely bad for steel structure.