四线铁路钢-混组合梁斜拉桥设计关键技术

Key Design Techniques for Steel-Concrete Composite Girder Cable-Stayed Bridge Accommodating Four Railway Tracks

上海斜塘特大桥主桥采用主跨260 m双塔斜拉桥,跨越斜塘航道,承载四线铁路。对2种边中跨比斜拉桥方案进行对比,根据中跨静活载挠跨比、静活载梁端转角和活载负反力等分析结果,确定边中跨比采用0.38,主桥跨径布置为(40+60+260+60+40)m;对比3种钢-混组合梁截面形式的主梁刚度、经济性及无砟轨道适应性,主跨梁体选取高3.5 m的分离式双箱钢-混组合梁,边跨及衔接处主跨8 m段采用混凝土梁;对比H形和花瓶形桥塔的结构性能、施工方案,选取高97 m的H形桥塔;综合考虑结构刚度、轨道板变形和施工控制,中、边跨斜拉索梁上间距分别取12 m和8 m,桥塔最外侧斜拉索倾角取30°;索塔、索梁均采用钢锚箱式锚固结构。大桥整体结构计算结果安全可靠;温度、列车等荷载组合作用下,桥梁竖向刚度、换算曲率半径均满足规范要求。

The main bridge of Xietang Bridge in Shanghai is a two-pylon cable-stayed bridge with a main span of 260 m,crossing the Xietang navigation channel and accommodating four railway tracks.The cable-stayed bridge schemes of two different side span to central span ratios were compared,and the side span to central span ratio was finally determined to be 0.38 in accordance with the analysis of the deflection-to-span length ratio of the central span under static loads,girder-end rotation angle under static loads and reaction forces of bearings under live loads,and the span arrangement would be 40,60,260,60 and 40 m.Three types of cross-sections of steel-concrete composite girder were compared from perspectives of main girder stiffness,economy and adaptability to ballastless tracks,and the split twin steel boxes and concrete slabs composite girder that measures 3.5 m deep was the final choice for the central span,while concrete box girders were adopted in side spans and the 8 m-long segments between the central span and the adjacent side spans.The mechanical properties and construction schemes of the H-shaped and vase-shaped pylons were compared,and the H-shaped pylons that are 97 m high were selected.To address the issues of structural stiffness,track plate deformation and construction control,the intervals of stay cable anchor points in the central and side spans are 12 and 18 m,respectively,and the outermost stay cables are allowed to incline 30°.The stay cables are anchored to the pylons and the deck via steel anchor boxes.The calculations demonstrate that the bridge structure is safe and reliable.Under the action of thermal and vehicle loads,the vertical stiffness and converted curvature radius meet the code requirements.