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对高温下钢交错桁架结构的抗侧力性能进行弹塑性有限元分析,考虑侧向力形式、火灾温度等因素,给出结构的侧向位移、弦杆挠度、弯矩等重要参数随温度的变化规律及结构受火后的塑性发展过程,分析其破坏形式与耐火极限。结果表明:受侧向力作用时,该体系顶点侧移随温度的变化主要可分为5个阶段,这与结构受火后各构件相继由弹性阶段进入塑性阶段密切相关。同时,结构的位移、弯矩及塑性发展区域呈现明显的非对称分布,由于火灾膨胀受限使部分构件极易发生塑性变形,并导致受火层出现一系列内力重分布,直至结构破坏。侧向力的作用方式对结构的极限抗火温度影响较小,且最先发生塑性破坏的位置均出现在受火楼层上弦杆中间节间与侧向力相对的端节点处,此区域应加强防火保护等级。以上研究结果可为该结构防火保护的优化设置提供参考。
The elastic-plastic finite element analysis of the lateral resistance of the staggered truss structure at high temperature is carried out. Considering the lateral force form and the temperature of the fire, some important parameters of the structure such as lateral displacement, chord deflection and moment are given. Changes in the law and structure by the plastic after the fire development process, analysis of the form of destruction and fire resistance. The results show that the lateral displacement of the system can be mainly divided into five stages by the lateral force, which is closely related to the phase of the structure after the fire from the elastic stage into the plastic stage. At the same time, the displacement, bending moment and plasticity of the structure show obvious asymmetrical distribution. Due to the limited expansion of the fire, some members are prone to plastic deformation and lead to a series of internal force redistribution in the fire layer until the structure is destroyed. The action of lateral force has little effect on the ultimate fire resistance temperature of the structure, and the location where the first plastic damage occurs appears at the end node opposite to the lateral force of the chord upper rod in the fire floor. This area should be strengthened Fire protection level. The above results can provide reference for the optimization of fire protection structure.