下穿铁路运行条件下双曲拱桥加固优化设计

南京长江大桥是长江上第一座由我国自行设计和建造的双层式公铁两用特大桥梁,是不可移动的文物。其公路桥与两侧桥台相接的引桥采用双曲拱桥,其中南岸引桥第56孔跨越老沪宁铁路线。经过近50年的运营,双曲拱桥的耐久性病害非常严重。施工图加固设计阶段拱下加固方案采用主拱圈下缘拱肋外包薄层混凝土为主要措施的增大截面加固法。涉铁孔双曲拱桥项目实施期间需保证铁路线正常运营,主拱圈加固实施难度很大。根据项目实际条件,结合结构计算分析,对56孔主拱圈创新性地采用拱背增大主拱圈截面,既提高了主体结构的承载能力,又保证了桥下铁路线的总体正常运营,达到了理想的加固效果。

Optimization Design of Strengthening the Two-way curved Arch Bridge While the undercrossing railway is operating

Nanjing Yangtze River Bridge is an extra major bridge crossing the Yangtze River with double decks serving highway and railway,designed and constructed by Chinese for the first time.Its approach bridges near the abutments of highway bridge are twin curved arch bridge,and the 56th hole of the south bank approach bridge crosses over the old Shanghai-Nanjing Railway line.After near 50years'service,this curved arch bridge is found to be suffering critical durability problems.In the reinforcement design stage of detailed engineering drawings,the reinforcement scheme under arch adopts the reinforcement method of enlarging the section of the outer thin-layer concrete of the arch rib at the lower edge of the main arch ring as the main measure.To ensure the normal operation of the railway line during the implementation of the curved arch bridge project makes the reinforcement of the main arch ring very difficult.According to the actual conditions of the project,combined with the structural calculation and analysis,for the main arch of the 56th span,the arch back is innovatively adopted to increase the section of the main arch ring,which not only improves the bearing capacity of the main structure,but also ensures the overall normal operation of the railway line under the bridge and achieves the desirable reinforcement effect.