铁路钢桥抗火性能和极限承载力研究  

Research on Fire Performance and Ultimate Bearing Capacity of Railway Steel Bridges

作　　者：杨正祥 崔闯[1] 胡文哲 范传斌 徐一鸣 YANG Zhengxiang;CUI Chuang;HU Wenzhe;FAN Chuanbin;XU Yiming(School of Civil Engineering,Southwest Jiaotong University,Chengdu 610031,China;Shenzhen-Zhongshan Link Adminstration Center,Zhongshan 528400,China;Poly Changda Engineering Co.,Limited,Guangzhou 510000,China)

机构地区：[1]西南交通大学土木工程学院,四川成都610031 [2]深中通道管理中心,广东中山528400 [3]保利长大工程有限公司,广东广州510000

出　　处：《铁道学报》2023年第3期70-79,共10页Journal of the China Railway Society

基　　金：广东省重点领域研发计划(2019B111106002);国家自然科学基金(51978579,52108176);四川省交通科技项目(R110121H01048)。

摘　　要：钢桥因轻质高强、跨越能力大而广泛应用于铁路的交通枢纽和咽喉工程,但近年频发的极端事件—桥梁火灾在铁路桥梁中屡见不鲜,严重威胁结构安全,导致结构产生不可恢复的损伤甚至倒塌。探究在火灾下桥梁性能退化规律,确定火灾下的铁路桥梁极限承载能力,是保证铁路桥梁安全运营的基本前提。此处以80 m单线铁路简支钢桁梁桥为研究对象,基于大涡模拟(LES)场模型理论,采用FDS火灾模拟软件分析确定桥上与桥下火灾场景温度场及升温曲线,结合有限元软件通过热-结构耦合分析火灾作用下结构温度场和极限承载能力。研究表明:桥上火灾场景火灾温度场在水平面内分布均匀,受火30 min左右时构件温度接近火灾烟气温度,钢材性能有所弱化;活载较大时,桥门架最先发生屈曲,屈曲系数为0.939,结构可能因高温导致热屈曲失稳。桥下火灾场景影响范围在16 m左右,下弦杆及下平纵联温度最高,桥下净空为5、10 m时,结构分别在受火6.8、22.5 min左右时达到耐火极限,桥下净空为15、20 m时,结构受火灾作用的影响较小;结构临界屈曲荷载随温度升高逐渐减小,各火灾场景结构极限承载能力分别下降34.1%、14%、2.2%、1.5%左右,对距地面15 m范围内的结构杆件、桥墩等考虑抗火安全防护措施。Steel bridges are widely used in key railway transportation projects for their light weight,high strength,and large spanning capacity.In recent years,extreme fires are getting more common in railway bridges,which seriously threaten the safety of the bridge structure,resulting in irrecoverable damage or even collapse of the structure.Exploring the degradation of bridge performance under fire and determining the ultimate bearing capacity of railway bridges under fire are the basic prerequisites to ensure the safe operation of railway bridges.Based on the study of an 80 m simply supported steel truss bridge of single-track railway,and the theory of large eddy simulation(LES)field model,the FDS fire simulation software was used to analyze and determine the temperature field and temperature rise curve of the fire scenes on the bridge and under the bridge.Combined with finite element software,the temperature field and ultimate bearing capacity of structures under fire were analyzed through thermal-structure coupling.The studies show that the fire temperature field of the fire scene on the bridge is evenly distributed in the horizontal plane,and the temperature of the components is close to that of the fire smoke when the components are exposed to fire for about 30 minutes,resulting in weakened steel performance.When the live load is large,the portal frame buckling first occurs,with the buckling coefficient of 0.939,which may lead to thermal buckling instability of the structure due to high temperature.The scope of the fire scene under the bridge is roughly 16 m,with the highest temperature of the lower chord and the lower horizontal longitudinal joint.When the clearance under the bridge is 5 m and 10 m,the structure reaches the fire resistance limit when it is exposed to fire for 6.8 min and 22.5 min,respectively.When the clearance is greater than 15 m,the structure is less affected by the fire.The critical buckling load gradually decreases with the the increase of temperature,and the ultimate bearing capacity of the s

关 键 词：铁路钢桥 大涡模拟法 升温曲线 火灾温度场 耐火极限 极限承载能力 

分 类 号：U448.13[建筑科学—桥梁与隧道工程]