大跨悬索桥吊索抗火性能与新防护结构研究

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...

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

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 protection and load-bearing load, a new structure based on nonlayer analysis for fire resistance of multieffect composite layer slings is presented by analyzing the mechanical characteristics of slings with different protective layer thicknesses. Finally, the relationship between the basic structural parameters of the sling core material and multi-effect composite layer material is discussed.