大跨度桁架拱外包混凝土吊架法施工技术

Lifting Frames Used to Construct Externally-Encased Concrete for Long-Span Truss Arch

成贵铁路鸭池河特大桥为主跨436m中承式钢-混结合提篮式拱桥,拱肋为钢桁架外包混凝土结构。拱肋外包混凝土采用吊架法施工。吊架由底模系统和侧模及其桁架组成,通过吊杆锚固在桁架拱下弦杆上。外包混凝土分节段分层浇注,施工过程中,采取增加上下弦连接杆、及时安装横撑和张拉扣索等技术措施控制桁架拱的附加应力。实践证明,该项施工方法中,吊架结构设计布置合理、操作安全简便,能控制主体结构的附加应力满足设计要求。

The Yachi River Bridge on Chengdu-Guiyang Railway is a half-through steel-concrete composite basket handle arch bridge with a main span of 436 m.The arch rib is a concrete-encased steel truss structure.The encasing concrete was continuously constructed by using lifting frames.The lifting frame consists of the base mould,the side mould and the truss,which was anchored to the lower chord of the truss arch by suspenders.The encasing concrete was cast section by section and layer by layer.During the casting process,the additional stresses in the truss arch was controlled by adding connection bars between upper and lower chords,timely installing lateral bracings and tensioning fastening stays.The engineering practice proves that the composition of the lifting frame structure is reasonable and meets the design requirements,which is safe and can facilitate operation and control the additional stresses in the main structure.