高速铁路主跨320 m钢-混部分斜拉桥无砟轨道适应性研究

Research on the Adaptability of Ballastless Track for 320 m Main Span Steel-Concrete Partially Cable-Stayed Bridge of High-speed Railway

南玉高铁六景郁江特大桥设计将钢-混部分斜拉桥结构引入时速350 km高速铁路领域,而300 m级以上大跨度桥上无砟轨道的竖向变形极易超限,影响列车通过的安全性和舒适性,因此,系统研究在此大跨桥梁结构上铺设无砟轨道的适应性十分必要。通过建立有限元及动力学模型,分析不同组合工况下无砟轨道结构的变形特点及动力特性,运用60 m弦测法探究各工况下无砟轨道的线形变化规律,从而确定大跨度钢-混部分斜拉桥铺设无砟轨道的适应性,并对设计和施工提出合理化建议。主要结论如下:在各种不利组合荷载作用下,桥上无砟轨道结构强度满足规范要求,列车通过大桥的各项安全性与舒适性指标均满足规范要求;混凝土收缩徐变和斜拉索升降温是影响无砟轨道线形标准的两大主因,应在无砟轨道施工前确保足够的沉降观测期和收缩徐变释放期,并充分考虑拉索的保温设计;在温度组合荷载作用下,桥上无砟轨道的60 m弦测不平顺幅值为6.79 mm,满足高速铁路静态验收标准;但在叠加列车荷载和收缩徐变后,变形弦测值均出现Ⅱ级及以上超限,通过合理设置预拱度后可有效改善轨道平顺性标准。

In the design of the Yujiang River Super Major Bridge on the Nanning-Yulin High-speed Railway,the steel-concrete partially cable-stayed structure is innovatively introduced into the high-speed railway field with a speed of 350 km/h.The limit vertical deformation of the ballastless track with a span of more than 300 m is likely to be exceeded,which affects the safety and comfort of the train passing through.Therefore,it is necessary to systemically study the adaptability of laying ballastless track on this large-span bridge.By establishing finite element and dynamic models,the deformation characteristics and dynamic characteristics of ballastless track structures under different combination conditions are analyzed,and the linear variation law of ballastless track under various conditions is explored by 60 m chord method,so as to determine the adaptability of laying ballastless track on large-span steel-concrete partially cable-stayed bridge.Reasonable suggestions are put forward for design and construction.The main conclusions are as follows:Under various unfavorable combination loads,the strength of ballastless track structure on the bridge meets the specification requirements,and the safety and comfort indices of trains passing through the bridge meet the specification requirements.The concrete shrinkage and creep,the temperature rise and fall of the bridges cable are two major factors affecting the linear standard of ballastless track,and it is necessary to maintain enough settlement observation period and shrinkage or creep release period,and fully consider the thermal insulation design of the cable before the construction of the ballastless track.Under the temperature combination load,the 60 m chord measurement of ballastless track on the bridge is 6.79 mm,which meets the static acceptance standard of high-speed railway.But under the superposition of train load and shrinkage creep,the deformed chord measurements of ballastless track exceeds the limit of grade II or above,and the track smoothness standard can be effectively improved by setting reasonable camber.