火灾高温下耐火保护钢梁设计荷载的分析

研究了火灾高温环境下耐火保护钢梁温度和结构的变化,运用有限元软件ANSYS模拟不同涂料厚度的耐火保护钢梁在标准温升模型、慢速和快速温升BFD模型3种温升曲线下,荷载作用不同时的最大挠度值,并与Robertson-Ryan准则中的最大挠度值比较,确定耐火保护钢梁的设计荷载值。结果表明,采用标准火灾模型代替自然火灾模型确定的设计荷载是不安全的;钢梁最高温度越高,设计荷载越低;随着涂料增厚,温升速率的改变对设计荷载值的影响逐渐明显。

Analysis of design load of fire-resistant steel beams under high temperature fire

Changes of temperature and deflection of steel beam covered with fire protective layer under fire were studied.The element software ANSYS was used to simulate the maximum deflection of steel beam with differently thick fire protective layer under different loads and 3 different temperature rise curves,such as standard heating modals,slow and fast BFD curve,and were compared with the maximum deflection of Robertson-Ryan criterion,to decide the design load of steel beam.Results showed that,using standard fire modal instead of nature fire model to decide the design load is unsafe;the design load gets lower while the maximum temperature of the steel beam getting higher;when the fire protective layer getting thicker,the change of temperature rise rate influences the design load bigger.