【作者】 王伟；

【导师】 康俊涛；

【作者基本信息】 武汉理工大学 ， 土木工程， 2020， 硕士

【摘要】 近年来,我国交通基础设施建设得到了高速发展,桥梁工程建设同样也取得了非凡成就,然而桥梁火灾事故却时有发生,对人民的生命财产造成了重大损失。相对于房屋建筑的火灾研究,我国在桥梁抗火研究方面存在诸多不足,尤其是对于大跨度钢结构桥梁的火灾研究成果甚少。随着桥梁建设的发展以及桥梁运输总量的提高,汽车火灾下桥梁结构的安全分析将会愈发重要。襄阳市苏岭山大桥是一座跨径布置为70 m+240 m+70 m的大跨度下承式钢桁架拱桥,为连接襄州区与东津新区的重要交通要道。本文以该桥为研究对象,基于结构性能化抗火设计的理念来完成汽车火灾下大跨度钢桁架拱桥结构性能分析以及抗火设计研究。本文的主要研究工作及结论如下:(1)对高温下钢材性能的典型研究成果进行了总结归纳,确定出合适的钢材热工参数与热力学参数,同时对各类典型的汽车火灾热释放率模型进行归纳分析,确定出用于苏岭山大桥火灾研究的汽车火灾热释放率模型。(2)分析了大跨度钢桁架拱桥的荷载传递特点,利用桥梁结构分析有限元程序Midas/civil计算出苏岭山大桥在正常运营阶段的各构件受力情况,并结合火灾对结构性能的影响规律,确定出苏岭山大桥在遭受汽车火灾时的最不利火灾发生场景。研究表明:苏岭山大桥在下弦杆拱脚位置以及主跨的跨中位置发生油罐车火灾时为最不利的火灾发生场景。(3)利用火灾动力学模拟软件FDS建立苏岭山大桥在下弦杆拱脚处以及主跨的跨中处发生油罐车火灾的热分析模型,得到大跨度钢桁架拱桥在汽车火灾下的三维瞬态温度场分布规律。研究表明:桥梁火灾温度场的空间差异性明显,不同空间位置的构件温度场差异很大,而火灾下钢构件沿截面厚度方向的温差相对较小,油罐车火灾作用下钢桁架拱肋构件的最高温度可达893.7℃。(4)利用有限元软件ABAQUS建立了全桥热-结构耦合分析模型,将汽车火灾下构件的三维瞬态温度场作为热荷载施加到热-结构耦合模型中,得出大跨度钢桁架拱桥在两种最不利火灾场景下的结构性能变化规律。研究表明:在油罐车火灾作用下,钢桁架拱肋构件存在屈服破坏的风险,火源附近的吊索承载力几乎完全丧失,全桥最大竖向位移变化可达-419.4mm。(5)分别对苏岭山大桥的钢桁架拱肋和吊索进行了防火设计研究,确定出钢桁架拱肋以及吊索的防火保护高度和防火涂料的填涂厚度。研究表明:桥梁设置防火保护措施后,能够有效的延缓和减弱汽车火灾对钢桁架拱桥结构性能的影响。更多还原

【Abstract】 In recent years,China’s transportation infrastructure construction has developed rapidly,and bridge engineering has also made extraordinary achievements.However,bridge fire accidents have occurred from time to time,causing significant losses to people’s lives and property.Compared with the field of housing construction,there are many deficiencies in the research of bridge fire resistance in China,especially for the fire research of long-span steel bridges.With the development of bridge construction and the increase in the total amount of bridge transportation,the safety analysis of bridge structures under automobile fires will become increasingly important.The Sulingshan Bridge in Xiangyang is a large-span down-through steel truss arch bridge with a span of 70 m + 240 m + 70 m.It is an important traffic link connecting Xiangzhou District and Dongjin New District.Taking this bridge as the research object,the structural performance analysis and fire resistance design research of large-span steel truss arch bridge under automobile fire were completed based on the concept of structural performance-based fire resistance design.The main research work and conclusions of this article are as follows:(1)The typical research results of steel properties at high temperature are summarized,and appropriate thermal and thermodynamic parameters of steel are determined.Summarize various typical models of heat release rate of automobile fire,Determine the model of heat release rate of automobile fire used for fire research of Sulingshan Bridge.(2)The load transfer characteristics of long-span steel truss arch bridges were analyzed.The bridge structure analysis finite element program Midas / civil was used to calculate the stress conditions of various components of the Sulingshan Bridge during normal operation,and combined with the impact of fire on structural performance The law determined the most unfavorable fire scene of Sulingshan Bridge when it suffered a car fire.Studies have shown that the Sulingshan Bridge is the most unfavorable fire scenario when a tank truck fire occurs at the lower chord arch foot position and the mid-span position of the main span.(3)Use the fire dynamics simulation software FDS to establish a thermal analysis model of a tank truck fire at the foot of the lower chord arch and the mid-span of the main span of the Sulingshan Bridge.Distribution of transient temperature field.The research shows that the spatial difference of the bridge fire temperature field is obvious,and the temperature of the members in different space locations is very different,while the temperature difference of the steel member along the thickness direction of the section under fire is relatively small,and the steel truss arch rib member under the action of a tank truck fire The maximum temperature can reach 893.7 ℃.(4)The finite element software ABAQUS is used to establish a full-bridge thermal-structure coupling analysis model.The three-dimensional transient temperature field of a component under a car fire is applied as a thermal load to the thermal-structure coupling model,and the large-span steel truss arch bridge is obtained.Changes in structural performance under the two most unfavourable fire scenarios.Studies have shown that under the action of a tank truck fire,the steel truss arch rib members are at risk of yield failure,the load capacity of the sling is almost completely lost,and the maximum vertical displacement change of the full bridge under the action of fire can reach-419.4mm.(5)The fire protection design of the steel truss arch ribs and slings of the Sulingshan Bridge was carried out to determine the fire protection height of the steel truss arch ribs and slings and the thickness of the fire-resistant coating.Studies have shown that setting fire protection measures can effectively delay and reduce the impact of fire on the structural performance of steel truss arch bridges.更多还原