九天湖大桥设计与建设实践

Design and Construction Practice of Jiutian Lake Bridge

九天湖大桥主桥设计为预应力混凝土梁拱组合曲线桥梁,采用自平衡拱脚推力的飞燕式结构,梁、拱、群桩基础固结的超静定体系,拱肋及主梁均采用抗扭刚度较大的箱型截面.该桥的设计建造有两大特点,一是该桥无拱上立柱,使得拱肋根部承受了较大的负弯矩;二是该桥建设在软土地基上,群桩承台有一定的柔度,影响结构的内力分布.在结构设计计算时通过将群桩等代成双柱考虑了软土地基的作用.桥梁施工阶段分析及验算表明结构的内力分布合理,结构处于安全状态.施工监控验证了这一点.该桥的建成为在软土地基上建设同类型桥梁提供了有益的借鉴.

The main bridge of Jiutian Lake bridge is designed as prestressed concrete beam arch composite curved bridge and adopts flying swallow type structure with self-balancing springing thrust. It belongs to hyperstatic system whose beam,arch and pile group are consolidated, and the box section with larger torsional rigidity is used in arch rib and girder. There are two peculiarities in the design and construction of this bridge. Firstly, there is no spandrel column, thus larger negative bending-moment is brought to spring. Secondly,there is a certain amount of flexibility in the capped slab of pile group because of the soft soil ground, which influences the distribution of internal force of the structure. The effect of soft soil ground is considered via replacing group piles by double-cylinder in the calculation of structure design. The distribution of internal force is proved reasonable by construction stage analysis and checking, so the bridge is in safe state,which is also validated by the conclusion of construction monitoring. The construction of this bridge offers beneficial use to reference for construction of congeneric bridge based on soft soil ground.