跨青尼罗河特大桥上部结构设计

Superstructure Design of Blue Nile River Bridge

跨青尼罗河特大桥为东部非洲区域首座大跨径双索面矮塔斜拉桥,主桥跨径布置为(100+180+100)m。大桥采用主梁与桥塔固结、墩梁分离的结构支承体系。主梁采用单箱三室变高度斜腹板预应力混凝土箱梁,中横梁为外挑式,桥塔悬臂支撑在中横梁两侧上,拉索横梁根据受力采用1.25 m或1 m外高。桥塔采用实心钢筋混凝土结构,利用轻钢龙骨+铝单板材料外包,形成船帆状桥塔造型,桥面以上塔高26.0 m(桥塔中心线处高度)。斜拉索采用1860 MPa镀锌钢绞线,双索面扇形布置,通过桥塔的抗滑分丝管后锚固于主梁两侧。全桥整体及细部分析结果表明,桥梁安全性满足规范要求。

The Blue Nile River Bridge is the first long-span extradosed bridge in East Africa.The main bridge has two identical extradosed structures arranged in parallel,each with a main span of 180 m and two side spans of 100 m.Each individual superstructure consists of three-cell prestressed concrete box girders with varying-depth oblique webs.The pylons,rising 26.0 m(measured at the centerlines of the pylons)above the deck,are solid reinforced concrete mono-column structures that are encased with light steel skeletons and aluminum sheets to resemble sails.The bridge has a total of 8 pylons and 4 cantilever-type pylon cross-beams.The pylon cross-beams are cast in situ integrally with the pylon columns and superstructure to be a rigid connection,and there are pot bearings on piers.The stay cables are made of galvanized steel strands with a tensile strength of 1860 MPa and are fanned out in double cable planes.The salient feature of the bridge is its diaphragms of the superstructure,which are braced with the inner vertical and outer oblique webs of the concrete box girders.These diaphragms measure 1.25 m or 1 m deep according to the load bearing requirements and cast in situ integrally with the anchor wedges of the stay cables.In the pylons,the stay cables are deviated via the multi-tube friction saddles.The overall and local finite element model analysis shows that the bridge structure reaches the required safety level.