南京长江大桥铁路层车致振动对公路层维修改造的影响分析

南京长江大桥于1968年建成通车，经过近50年的铁路（约400列次·d^-1）、公路（高峰期约10万veh·d^-1）运营，公路正桥桥面系破损严重、屡修屡坏，亟需进行全方位性能提升。其中，列车频繁通过所致高频强扰动带来的结构安全是该维修改造的关键技术难题；通过车-桥耦合振动分析得到南京长江大桥维修改造前、中、后各阶段列车动载作用下的结构响应，从振动分析角度评估其维修改造时的结构动力安全。首先，建立不同改造阶段南京长江大桥精细化有限元模型，并验证其动力模拟的准确性；进而基于车-桥耦合空间振动理论，借助MATLAB与ANSYS平台编制南京长江大桥维修改造车致振动分析程序，同时基于既有文献算例完成其分析准确性验证；最后利用该程序得到公路层不同改造阶段列车驶过铁路层时主梁结构振动位移、加速度与应力时程，并计算关键节点的疲劳损伤与剩余寿命。研究结果表明：南京长江大桥改造中，列车过桥结构动载响应与改造前后振动响应规律相同，但改造后其位移量降低，新安装正交异性钢桥面板的轻质高强特性会改善全桥动力行为；旧桥面系拆除与新桥面系安装过程中，列车通行并不会影响其维修改造的结构安全；改造后其动载下疲劳损伤值不大，理论剩余寿命很长，均远超其服役年限。

Influence on Highway Bridge Deck System Reconstruction by Train-passing-railway Induced Vibration of the Nanjing Yangtze River Bridge

The Nanjing Yangtze River Bridge has been open to the public since 1968, with daily traffic of 400 railway trains and 100 000 highway vehicles. After a 50-year service period, the highway bridge deck system has been damaged several times and requires immediate maintenance and mechanical improvement. Based on the train-bridge coupling analysis, the behaviors of the Nanjing Yangtze River Bridge under the passing train were investigated for different stages-before, during, and after the reconstruction. The reconstruction safety of the structure was evaluated from the viewpoint of vibration. First, a finite element model was established to simulate different reconstruction stages. The accuracy of the dynamic modeling was verified using the vibration test data. Then, using the theory of train-bridge coupling vibration, an analysis platform was programmed using MATLAB and ANSYS software. This program was verified using existing test examples. The time-varying vibration displacement, acceleration, and stress of the truss induced by the passing train were obtained for each reconstruction stage using this program. The fatigue damage and remaining ages were simultaneously calculated. The results showed that the vibration behavior induced by the passing train during the reconstruction is similar to that before and after reconstruction. Lower displacements of the girder were observed after reconstruction. The newly installed orthotropic steel deck with a light density and high strength could improve the dynamic performance of the bridge. The passing train would not influence the structural safety during the reconstruction, and only a small amount of fatigue damage could be induced after the reconstruction with a longer theoretical remaining age than its service stage.