昌九高铁扬子洲赣江公铁大桥西支主桥方案比选

Options for West Main Bridge of Yangzizhou Ganjiang River Rail-cum-Road Bridge of Nanchang-Jiujiang High-Speed Railway

昌九高铁扬子洲赣江公铁大桥西支主桥为承载时速350 km高速铁路的大跨度公铁合建桥,主跨320 m,公铁混层对称布置,下层桥面中间布置双线无砟轨道高速铁路、两侧布置双向4车道城市主干路,上层桥面布置双向8车道城市快速路。结合桥址区建设条件,对跨径布置为(64+128+320+128+64)m箱桁组合梁斜拉桥和钢桁架拱桥2种桥型方案进行对比,结果表明箱桁组合梁斜拉桥受力明确,具有较好的施工稳定性和良好的经济性,为选定方案。针对扇形双索面密索体系、扇形双索面稀索体系和竖琴形双索面密索体系3种体系斜拉桥方案,从结构受力性能、施工难度、经济性、景观性等方面进行综合分析,最终选择受力合理、施工简便、经济性优、景观效果好的竖琴形双索面斜拉桥方案。桥塔采用花瓶形构造,主梁采用中间双桁、带挑臂的箱桁组合截面,结构受力合理,具有优良的整体性和结构刚度。

The west main bridge of Yangzizhou Ganjiang River Rail-cum-Road Bridge of Nanchang-Jiujiang High-speed Railway is a long-span cable-stayed bridge with a main span of 320 m.As a double-decker,the bridge allows for a train travelling speed of 350 km/h,where the lower deck accommodates two ballastless high-speed railway tracks(arranged in the center of the deck)and four lanes of urban trunk roads(two on each side of the railway track and for the same direction),and the upper deck carries 8 freeway lanes.To address the construction conditions at the bridge site,two options were presented,one was a cable-stayed bridge that was arranged in a main span of 320 m,two side spans of 128 m and two end spans of 64 m and had a composite superstructure consisting of steel trusses and steel-box-girder decks,and the other was a steel truss arch bridge.The comparison indicated that the cable-stayed bridge with steel truss and box composite superstructure is superior to the steel truss arch bridge in terms of load bearing performance,construction stability and economy,which was finally selected.Three types of stay cable arrangements,including the double fan planes of dense stay cables,double fan planes of sparse stay cables and double harp planes of dense stay cables,were compared from aspects of structural load bearing performance,ease-of-construction,economy and landscaping effect.The double harp planes of dense stay cables was determined as the final scheme.The pylons are vase-shaped structures,the superstructure consists of the central trusses with outriggers and two levels of steel-box-girder decks.All the load bearing performance,stability and stiffness of the bridge structure reach the expected levels.