【摘要】 针对油罐车火灾对钢结构桥梁造成的严重威胁,选取四跨双肋钢板组合连续梁(4×35 m)作为研究对象。根据油罐车火灾燃烧特点选取最为贴近的碳氢(HC)火灾升温曲线,以实际受火特征还原了4种受火模式,采用热-力耦合计算方法,建立有限元模型,并对模型有效性进行了验证。首先分析了油罐车火灾作用下钢板组合梁的温度场,然后推导了火灾下双肋钢板组合梁塑性抗弯承载力计算方法,基于温度场分析结果计算了油罐车火灾下钢板组合梁正弯矩区域的抗弯承载能力衰退曲线,分析4种火灾作用下钢板组合梁的挠度变化过程,采用抗弯承载力和挠度破坏准则得出组合梁的耐火极限;最后对4种火灾场景下钢板组合梁的破坏形态进行了分析。研究结果表明:油罐车火灾下,钢材整体升温幅度远大于混凝土,组合梁截面沿梁高方向出现明显的温度梯度,其最大值为1 020℃,这种温度梯度导致的热拱是钢板组合梁在延火初期下挠的主要原因;截面抗弯承载力在延火初期降低缓慢,在进入高温阶段后截面抗弯承载力急剧降低,最终在30 min左右降低至荷载效应以下,组合梁破坏;在火灾作用下组合梁挠度总体呈三阶段发展,边跨受火长度对组合梁挠度变化影响较大,边跨受火长度越大,挠度增长越快;采用挠度准则判断组合梁的破坏相较于抗力准则偏于不安全,并基于抗力破坏准则对挠度准则进行了修正;边跨在火灾作用下表现为整体垮塌破坏,中跨受火表现为混凝土板的挠曲破坏和钢梁的鼓胀破坏。更多还原

【Abstract】 Aimed at the serious threat to steel bridge caused by tanker fire, a four-span double-ribbed steel-concrete composite continuous bridge girder(4×35 m) was selected as research object. According to characteristics of tanker fire, the closest HC temperature-time curve was selected, and four fire modes of tanker fire were restored according to the actual fire characteristics. The finite element model was established using thermodynamic coupling calculation method and validated by experimental results. Firstly, the temperature field of steel-concrete composite bridge girder under tanker fire was analyzed. Then, the calculation method of flexural capacity of double-ribbed steel-concrete composite bridge girder was proposed, and degradation of flexural capacity in positive moment region under tanker fire was calculated based on the results of temperature field. In addition, the deflection progression of steel-concrete composite bridge girder under different fire scenarios was analyzed, and fire resistance of steel-concrete composite bridge girder was obtained, using flexural capacity and deflection failure criterion. Finally, the failure modes of the steel-concrete composite bridge girder under different fire scenarios were studied. The results show that the temperature rise of steel is much larger than that of concrete. The steel-concrete composite bridge girder presents an obvious temperature gradient along the girder depth and its maximum value is 1 020 °C. The thermal bowing caused by temperature gradient is the main reason for deflection of steel-concrete composite bridge girder at the initial stage of fire. Flexural capacity decreases slowly at the initial stage of fire, after entering high temperature stage, flexural capacity decreases rapidly. Finally, at about 30 min, failure of the steel-concrete composite bridge girder occurs, when flexural capacity drops below the bending moment resulting from applied load. The general trend of deflection progression can be grouped into three stages, fire exposure length of side span has great influence on deflection progression of the composite girder, and the faster deflection increases with the larger fire exposure length. Using deflection criterion to judge failure of composite bridge girder is unsafe compared with flexural capacity criterion, and deflection criterion is revised based on flexural capacity criterion. Side span exposed to tanker fire presents fully collapse and mid-span presents large deflection of concrete slab and swell of steel girder. 3 tabs, 11 figs, 32 refs.更多还原