冷弯薄壁槽钢-混凝土组合梁抗火性能参数分析

基于ANSYS热分析结果，建立冷弯薄壁槽钢-混凝土组合梁在标准火灾作用下的热-结构耦合有限元计算模型，对荷载水平、混凝土强度、槽钢截面几何尺寸、防火涂层厚度、加载位置和加载方式等不同影响因素下的组合梁抗火性能进行有限元分析。结果表明：防火涂层厚度和荷载水平对组合梁抗火性能的影响显著，槽钢截面腹板高度和腹板厚度次之，混凝土强度、加载位置、加载方式和槽钢翼缘厚度等因素对组合梁的抗火性能影响很小，可以忽略不计；防火涂层厚度一定时，组合梁的耐火极限随荷载水平的提高而降低；荷载水平一定时，组合梁的耐火极限随防火涂层厚度的增加而呈非线性提高；填充混凝土可有效降低钢梁截面的温度，产生温升延时效应，在升温前期，冷弯薄壁槽钢-混凝土组合梁的温度低于未填充混凝土的型钢梁，降幅可达15％~60％。在ISO-834标准火灾作用下，组合梁跨中挠度 δ=l/25 可作为其达到耐火极限的判别标准。

Parametric analysis of fire-resistant behavior of cold-formed thin-walled channel steel concrete beam

Based on the thermal ANSYS analysis,a numerical model for fire-structure coupling analysis of the cold-formed thin-walled channel steel concrete beam under the standard fire is established.The fire-resistant behavior of the composite beam in different influence factors,including the static loading level,the concrete strength,the channel steel section geometry,the fire protection coating thickness,the loading location and the loading pattern,were numerically simulated and analyzed.The numerical results show that the effects of the fire protection coating thickness and the loading level on the fire-resistant of composite beam are significant.The influence of the height and the thickness of channel steel web also should be considered.The concrete strength,the loading location and the loading pattern have little effect on the fire-resistance of the composite beam and can be neglected.The results also show that the fire-resistance of the composite beam will be reduced with the loading level increases for a certain fire protection coating thickness and it will nonlinearly increase with the fire protection coating thickness increases for a certain loading level.The filled concrete can effectively reduce the temperature of the steel beam section and result in temperature elevation delay effect.In the early stage of temperature elevation,the temperatures of the cold-formed thin-walled channel steel concrete beam are lower than those of unfilled channel steel beam,and the temperature reduction may reach 15%~60%.In the ISO-834 fire the mid-span deflection δ=l/25 can be used as the criterion to determine the fire resistance of the composite beam.