主跨588 m非对称矮塔公铁两用斜拉桥设计研究

Research on Design of Asymmetric Short-Pylon Rail-cum-Road Cable-Stayed Bridge with 588 m Main Span

商合杭铁路芜湖长江公铁大桥受建设条件限制,主桥设计为主跨588m的非对称矮塔斜拉桥。主梁采用双层桥面箱—桁组合结构钢梁,下层铁路桥面为钢箱结构,上层公路桥面为密横梁体系的正交异性钢桥面板结构。该主梁结构具有强箱弱桁的受力特性,解决了该桥塔矮、索平以及主梁水平轴力大的问题。斜拉索采用抗拉强度2000MPa的高强度锌铝合金镀层平行钢丝拉索,以承受高达1.5×10^4kN的斜拉索轴力。将斜拉索锚固于主梁下弦,使斜拉索获得相对较大的倾角从而提高结构体系刚度。芜湖侧桥塔墩基础采用平面尺寸为65m×35m的大型设置沉井基础,克服了该侧桥塔墩基础深水、裸岩的困难建设条件。

Restricted by the construction conditions, the main bridge of Wuhu Changjiang River Rail-cum-Road Bridge on Shangqiu-Hefei-Hangzhou railway is designed as an asymmetric short-pylon cable-stayed bridge having a main span of 588 m. A box-truss composite structure with double decks is used in the main girder. A steel box girder is applied for the lower-layer railway deck, while an orthotropic steel deck structure with dense crossbeam is applied for the upper-layer highway deck. This type of main girder, which possesses the characteristics of strong box girder and weak truss, is favourable for solving the prolems caused by short pylons, small-angle stay cables and giant axis force of the main girder. Parallel steel wire stay cables coated with Zn-Al alloy with 2 000 MPa high strength are used to bear the axis force of cables which is up to 1.5×10^4 kN. Stay cables are anchored in the lower deck to increase the angles which can improve the rigidity of the whole structure. Moreover, large-scale setting type open caisson foundation which has a plane size of 65 m×35 m is used in the pylon foundation of Wuhu side to overcome the difficult construction conditions caused by deepwater and exposed bedrock.