深江铁路洪奇沥公铁两用大桥主桥方案构思与总体设计

Conceptualization and Overall Design of Main Bridge of Hongqili Rail-cum-Road Bridge of Shenzhen-Jiangmen Railway

深江铁路洪奇沥公铁两用大桥主桥采用(3×100+808+3×100)m超短边跨钢-混组合混合梁斜拉桥,一跨跨越通航水域。该桥公铁分层布置,上层布置8车道城市快速路,下层布置4线铁路。主梁采用倒梯形双主桁截面,桥面布置紧凑、受力明确、经济性好。中跨主梁采用板桁-箱桁组合结构钢梁,桥面结构参与主桁受力,具有高效综合性能。边跨主梁采用矩形钢管混凝土叠合板-桁组合梁,融结构受力和锚固压重于一体,叠合板采用32 cm厚预制板+40 cm厚现浇层。钢-混结合段采用“钢格室+承压板”构造,钢-混结合面位于桥塔向中跨侧4.6 m。桥塔采用H形混凝土塔,基础采用35根直径4.0 m的大直径钻孔灌注桩。斜拉索采用标准抗拉强度2000 MPa的平行钢丝成品索,最大规格为PES(C)7-547。索梁锚固采用副桁弦杆节点兜底钢锚箱结构,传力可靠、抗疲劳性能好。索塔锚固创新地采用自平衡交叉混合锚固技术,以适应大规格斜拉索锚固。钢桁梁采用“纵向分段、横向分区”制造、运输、现场吊装的施工方案。

The main bridge of Hongqili Rail-cum-Road Bridge carrying a section of the Shenzhen-Jiangmen Railway is a cable-stayed bridge with a main span of 808 m,crossing the navigation channel with no support of river piers.The superstructure,accommodating 8 lanes of freeway on the upper deck and 4 track lines on the lower deck,is of an inverse-trapezoidal cross-section,with two planes of vertical steel trusses,which reveals a balance between the structural configuration and economic performance.The steel boxes connecting the two planes of steel trusses form the two levels of decks of the central span and act compositely with the steel trusses.The superstructure in the three spans of 100 m on each side of the main span consists of two planes of steel trusses and the connection concrete panels acting compositely with the rectangular steel tubes of the trusses that are filled with concrete,the concrete-filled steel tubes are on the one hand engaged in load bearing performance of the bridge,and on the other hand support cable-girder anchorages and serve as counterweights as well.The connection concrete panels involve 32 cm-thick precast concrete slabs and 40 cm-thick cast-in-place layers.The steel-concrete joint section features the latticed chamber and bearing plates,with the steel-concrete interface located in the center span,4.6 m to the pylon.The pylons are H-shaped concrete pylons,each supported by 35 bored piles of 4.0 m diameter.The stay cables are composed of parallel steel wires with a nominal tensile strength of 2000 MPa,with the highest grade of PES(C)7-547.To create reliable load transfer path and improve the fatigue strength of the bridge,the steel anchor boxes in the superstructure were encircled by the node of the chords of the secondary trusses.The large stay cables are anchored to the pylons by the combined self-balancing and cross-over technique.The steel trusses were divided into segments in the longitudinal direction and zones in the transverse direction to facilitate fabrication and transportation,and assembled at the bridge site.