波形钢腹板-钢底板组合箱梁抗火性能研究

Research on Fire Resistant Performance of Composite Box Girder with Corrugated Steel Web and Steel Bottom Plate

为研究波形钢腹板-钢底板组合箱梁的抗火性能,以某简支波形钢腹板-钢底板组合箱梁为研究对象,采用ANSYS软件建立组合梁的热-力耦合有限元模型,分析组合梁的温度分布、挠度变化、抗弯承载力衰退规律,并进行参数敏感性分析。结果表明:火灾作用下波形钢腹板-钢底板组合箱梁截面沿高度方向产生较大的温度梯度;组合梁挠度在火灾暴露初期、中期和后期三阶段分别呈现缓慢增长、快速增长和极速增长的特征;组合梁抗弯承载力衰退速率随受火时间的增加呈现先增大后减小的趋势;组合梁耐火时间随着荷载比的增大而减小,改变钢腹板型号和腹板加劲肋数量对组合梁耐火时间影响较小,增设底板加劲肋可有效延缓组合梁的挠度发展进入火灾暴露后期,从而增加其耐火时间。

An existing simply-supported box girder with corrugated steel webs and steel bottom plates is applied as a case to study the fire resistant performance of the bridge of similar type.A finite element model reflecting the thermal-force coupling was built up in ANSYS to analyze the temperature distribution,deflection variation and flexural strength attenuation and carry out parametric analysis.The results indicate that there exists significant thermal gradients along the depth of the composite box girder with corrugated steel webs and steel bottom plates.The deflection of the composite box girder increases slowly in the initial stage of a fire disaster,then rapidly and dreadfully increases in the middle and late stages,respectively.The flexural strength attenuation rate of the composite box girder increases for a time,but decreases afterwards as the fire exposure time lasts longer.The fire enduring time of the composite girder is reduced as the load ratio increases,changing the specs of webs and the number of stiffening ribs of the webs has minimal influence on the fire enduring time of the composite girder.Adding stiffening ribs to bottom plates can delay the deflection of the composite girder developing into the late stage of fire exposure,thereby making the composite girder more fire resistant.