重庆大溪河特大桥主桥设计

Design of Main Bridge of Chongqing Daxi River Bridge

重庆大溪河特大桥主桥为(92+168+650+168+92)m双塔双索面组合梁斜拉桥,采用半飘浮体系,塔梁之间设置竖向支承、横向限位和纵向阻尼,有利于降低梁端位移和桥塔内力。桥塔采用神女造型的钻石形桥塔,钢筋混凝土空心塔柱。主梁采用双边工字形钢-混组合梁,桥面板采用预应力混凝土和超高性能混凝土(UHPC)预制板,板间湿接缝采用UHPC填筑。边跨采用“压重+结构调整+竖向锚索”的配重方式,防止运营阶段过渡墩及辅助墩支座出现负反力。斜拉索索面呈扇形布置,共208根,为抑制斜拉索风雨激振,斜拉索外护套上设置双螺旋线,在索梁锚固端和索塔锚固端设置内、外阻尼器。索梁锚固采用外置钢锚管形式的钢锚梁,塔上斜拉索分别锚固在上中塔柱连接段隔板及塔壁、上塔柱的钢锚梁上。辅助墩和过渡墩均采用花瓶形空心墩,桥塔和桥墩基础采用整体式承台+群桩基础。主梁采用导流板+下中央稳定板的组合气动措施,风洞试验结果表明:该气动措施能有效控制主梁的涡激振动振幅在安全范围。

The main bridge of Chongqing Daxi River Bridge is a two-pylon,composite girder cable-stayed bridge consisting of a main span of 650 m,two spans of 168 m and two spans of 92 m.There are vertical supports,transverse restricters and longitudinal dampers installed in-between the superstructure and the pylons,forming a semi-floating system that is beneficial to reduce girder-end displacements and internal forces in pylons.The pylons are diamond-shaped structures with hollow reinforced concrete columns,mimicking standing goddesses.The superstructure consists of two steel edge I girders that act compositely within the prestressed concrete deck panels with a UHPC overlay,the deck panels were stitched by UHPC.To avoid the uplift of bearings on top of the transition and auxiliary piers at service stage,the side spans were counterweighted by placing counterweights,performing structure adjustment,and adding vertical anchor cables.The total 208 stay cables are arranged in double fan planes,and each sheathed stay cable is fitted with helical ribs to suppress rain-wind induced vibrations.The stay cables are anchored to the superstructure with external tube-type steel anchor beams,with dampers installed inside the superstructure,while to the pylons via the diaphragms and pylon walls of the joint sections of the upper and intermediate pylon columns and the steel anchor beams in the upper pylon columns.The auxiliary and transition piers are hollow vase-shaped structures.The pylons and all the piers rest on integral pile caps that are supported by bored piles.The superstructure is equipped with deflectors and central stabilizers to improve aerodynamic stability.The data of wind tunnel tests demonstrate that the vortex-induced vibrations of the superstructure are effectively controlled within the safe amplitude ranges.