大跨悬索桥吊索抗火性能与新防护结构研究  

Research on Fire Resistance Performance and New Structure Idea for Long-span Suspension Bridge Slings

作　　者：刘伟庆[1] 宋佳润 李雪红[1] LIU Wei-qing;SONG Jia-run;LI Xue-hong(School of Civil Engineering,Nanjing University of Technology,Nanjing 210094,Jiangsu,China)

机构地区：[1]南京工业大学土木工程学院,江苏南京210094

出　　处：《中国公路学报》2022年第1期222-237,共16页China Journal of Highway and Transport

基　　金：国家重点研发计划项目(2017FYC070723405);国家自然科学基金项目(51876088)。

摘　　要：为了使造型优美的大跨悬索桥能更好地保持原始设计性能,以获得更长久的安全使用状态,梳理分析了构成索桥吊索危害的最不利火灾工况,构建计算仿真模型,分析吊索极限断裂情况,提出了防护和承重载荷兼顾的新型吊索结构。在分析此方面研究成果的基础上,按照背景可通行的危害标的物选择油罐车火灾燃烧模型,依据试验数据和引用参考确定吊索材料热力学性能函数和火灾源燃烧模型;使用FDS软件建立火灾源火焰燃烧模型,分析不同风速火灾源的温度分布规律,得出风速为14 m·s^(-1)火灾源热释放率300 MW为最不利火灾工况。然后采用STAR-CCM+软件建立吊索热力耦合数值模型,获得吊索火灾高温断面应力随火灾源温度及力载荷的变化关系;构建无层析的复合层材料吊索热力结构耦合模型,分析相同热力条件下单层防护和不同复合层结构厚度吊索力学性能;应用ANSYS软件分析索桥整体结构热力学性能,获得最不利火灾条件下跨中吊索极限断裂条件,以及相邻吊索力学特征,发现跨中相邻吊索断裂根数大于3根,会引起吊索连续断裂并可能引起索桥坍塌的力学状态。最后依据吊索承载与防护相结合的新思想,设计了一种无层析的多效复合层吊索抗火新结构,分析了不同防护层厚度吊索的力学特征变化,指出了吊索芯材料与多效复合层材料的基本结构参数匹配量变关系。To maintain the performance of the original design and achieve long-term safe use of a beautiful long-span suspension bridge, the most unfavorable fire conditions that contribute to the damage of suspension cables were recorded and analyzed. Computational simulation models were built, the ultimate fracture of the slings was analyzed, and a new structural sling was developed considering protection and load-bearing load. First, previous research results were analyzed. Based on the analysis, a fire model of a large oil tanker was selected, and the performances of the sling and fire source combustion model were evaluated according to the test data and references. By using Fire Dynamics Simulator software, a flame combustion model of the fire source was established, and the temperature distribution law of fire sources with different wind speeds was analyzed. The heat release rate of a 300 MW fire source with a wind speed of 14 m·s^(-1)is the most unfavorable working condition of fire. Second, STAR-CCM+ software was used to establish a thermal-mechanical coupling numerical model of the slings. In addition, the relationship between the high-temperature cross-section stress of the slings and temperature of the fire source and force load was obtained. By constructing a thermal structure coupling model of a composite layer sling without chromatography, the mechanical properties of the slings with single-layer protection and composite-layer structures with different thicknesses under the same thermal conditions were analyzed. ANSYS software was used to analyze the thermodynamic performance of the entire structure of the cable bridge, and the limit fracture conditions of the middle-span hangers and the mechanical characteristics of the adjacent hangers were obtained under the most unfavorable fire conditions. Thus, when the fracture number of adjacent slings is more than three, the suspension cable breaks continuously, even after the collapse of the suspension bridge. Finally, based on the new idea of combining cable protec

关 键 词：桥梁工程 大跨悬索桥 抗火性能 连续断裂 吊索新结构 安全防护 

分 类 号：U448.25[建筑科学—桥梁与隧道工程]