基于现场实测的大跨钢桁悬索桥疲劳可靠度分析  

Analysis on Fatigue Reliability of Long-span Steel-turss Suspension Bridge Based on Field Measurement

作　　者：韩艳 李凯 孙一婵 蔡春声[2] HAN Yan;LI Kai;SUN Yi-chan;CAI Chun-sheng(School of Civil Engineering,Changsha University of Science and Technology,Changsha Hunan 410114,China;Department of Civil and Environmental Engineering,Louisiana State University,Baton Rouge LA 70803,USA)

机构地区：[1]长沙理工大学土木工程学院,湖南长沙410114 [2]路易斯安那州立大学土木与环境工程系,美国路易斯安那州,巴吞鲁日70803

出　　处：《公路交通科技》2020年第4期72-80,共9页Journal of Highway and Transportation Research and Development

基　　金：国家自然科学基金项目(51822803,51678079,51778073);湖南省杰出青年基金项目(2018JJ1027);湖南省教育厅优秀青年基金项目(16B011)。

摘　　要：为了研究大跨度钢桁架悬索桥桁架杆件在随机车流荷载作用下的疲劳可靠度,首先以某大跨钢桁悬索桥为工程背景,建立梁-壳混合单元空间桁架主梁有限元模型,确定钢桁加劲主梁应力的关键位置。然后,针对主桁梁应力关键点对该桥进行测点布置并进行了短期的动态应变监测。随后,采用核密度估计方法建立基于小样本的日等效应力幅和日循环次数的概率分布模型。最后,基于Palmgren-Miner线性累积损伤准则及欧洲钢结构设计规范Eurocode 3的疲劳强度S-N曲线建立了关键构件的疲劳损伤极限状态方程,采用Monte-Carlo方法计算分析了不同交通增长系数下所测关键构件的时变疲劳可靠度。研究结果表明:该大跨钢桁悬索桥钢桁架主梁结构在车辆荷载下处于低应力状态,但是应力循环次数较高;车辆荷载对主横桁架外侧斜腹杆产生的疲劳荷载效应大于其他杆件,即斜腹杆更容易发生疲劳破坏,需引起高度关注;在短期监测情况下,采用核密度方法建立基于小样本的概率模型进行大桥疲劳可靠度分析是可行有效的;交通量的增长对疲劳可靠度指标的影响很大,车辆荷载引起的疲劳问题不容忽视;但总体来说所测关键构件的疲劳可靠度水平较高,在设计基准期内,发生疲劳破坏的可能性极小。In order to investigate the fatigue reliability of the truss members of long-span steel truss suspension bridges under random traffic flow load, first, on the background of a long-span steel truss suspension bridge, the spatial FE model of the truss girder with beam-shell hybrid elements is established, and the critical locations of the stresses of the steel truss stiffening girder are determined. Subsequently, the measuring points on the bridge corresponding to the key stress points of the main truss girder are arranged, and the short-term strains are monitored. Then, the probability distribution model of daily equivalent stress range and daily cycle number based on small samples is established by using kernel density estimation method. Finally, based on the Palmgren-Miner linear cumulative damage rule and the fatigue strength S-N curve in Eurocode 3, the fatigue damage limit state equation of the critical members is established, and the time-dependent fatigue reliability of the measured key components under different traffic volume growth factors is analyzed by using Monte-Carlo method. The result shows that(1) the steel truss girder of the bridge is in a low stress state under vehicle load, but the stress cycling number is high;(2) The fatigue load effect of vehicle load on the outside oblique web members of main transverse truss is greater than other members, that is, the oblique web member is more prone to fatigue failure, which should be paid more attention to;(3) in the case of short-term monitoring, it is feasible and effective to establish a probability model based on small samples by using nuclear density method for bridge fatigue reliability analysis;(4) the increase of traffic volume has a great influence on the fatigue reliability, and the fatigue problem caused by vehicle load cannot be ignored;(5) however, the fatigue reliability level of the measured key components possesses a high level, and the possibility of fatigue failure is very unlikely during the design reference period.

关 键 词：桥梁工程 疲劳可靠度 现场实测 大跨钢桁悬索桥 核密度估计 

分 类 号：U448.25[建筑科学—桥梁与隧道工程]