大跨悬索桥主缆抗火性能及其防护

Fire resistance performance and protection of long-span suspension bridge main cable

为了分析主缆的抗火性能并提出适宜的抗火防护方案,基于实际工程,采用油罐车燃烧火灾模型计算方法,分别从油罐车火灾燃烧的形式、火灾发生的位置、火灾燃烧的状态等方面进行对比分析,确定悬索桥最不利火灾场景为无风工况+油罐火灾+顶面和近主缆侧面燃烧+跨中靠近吊索位置.采用Ansys软件分析最不利火灾场景下主缆的温度分布及耐火极限,得到主缆的耐火极限为48 min,最大失效厚度为90 mm.通过对各类防火材料分析和调研,提出高硅氧复合材料防火结构;在高温试验60 min后,试件防火结构内侧温度为484℃,压缩后的防护结构的抗火性能略有提升.基于试验结果并结合数值模拟,得到10 mm厚高硅氧复合防火结构;该结构可以满足在火灾发生后60 min主缆外表面温度不超过300℃的抗火设计目标.

In order to analyze the fire resistance performance of the main cable and to propose the appropriate fire resistance protection scheme,based on the actual project,the calculation method for tank truck fire model was adopted to make a comparative analysis from the aspects of the tank truck fire burning form,the fire location and the fire burning state.The most unfavorable fire scenario of a suspension bridge was determined as windless condition+oil tank fire+top surface and near main cable side combustion+mid-span near sling position.The Ansys software was used to analyze the temperature profile and the fire resistance limits of the main cable in the most unfavorable fire scenarios.The fire resistance limit of the main cable was 48 minutes and the maximum failure thickness was 90 mm.Through the analysis and the investigation of various fireproof materials,a fireproof structure of high-silica composite material was proposed.After 60 min of an elevated temperature test,the inner temperature of the fireproof structure of the specimen was 484℃,and the fire resistance was slightly improved after the compression of the protective structure.Based on the test results and the numerical simulation,a 10 mm thick high-silica composite material fireproof structure was obtained.The obtained structure could meet the fire resistance design goal that the outer surface temperature of the main cable should not exceed 300℃after 60 min of a fire.