大跨双铰高低拱座钢桁架拱桥设计关键技术

Key Design Techniques of Long-Span Two-Hinge Steel Truss Arch Bridge with High and Low Arch Seats

湖北宜来高速溇水河大桥跨越宽300 m以上的U形沟谷,两岸地势陡峭,两岸山体高差近36 m,为减少施工开挖对环境的破坏、保证结构安全性和经济性,经方案比选,该桥最终采用附加内力小、适应基础变位能力强、因地制宜的主跨310 m双铰高低拱座中-下承式钢桁架拱桥。为满足高低拱座拱桥的结构受力、提高工业化制造效率,该桥拱轴线采用虚拟计算跨径340 m、矢高86.2 m、拱轴系数1.7的整体悬链线方案。主拱肋采用2片N形桁架结构,单片拱肋采用等截面扁平钢箱结构,主桁节点采用整体栓焊节点,2片拱肋桁架横向中心距27 m,通过米撑及K撑连接。桥面系采用传力明确、经济性好的纵梁结构体系钢-混组合梁,且在端横梁外侧增加小边跨解决边跨梁端出现负反力的问题,梁端设置速度锁定器约束装置。为解决拱脚在多重荷载作用下的受力及耐久性难题,提出拱脚铰轴采用摇摆式铰轴构造。整体及局部分析表明,该桥具有较好的静、动力性能。

The Loushui River Bridge of Yidu-Laifeng Expressway in Hubei Province crosses a U-shaped ravine that is more than 300 m wide.The sides of the ravine are steep and the height difference of the hills at the two sides of the ravine approximates 36 m.To minimize the damage of environment caused by construction excavation and ensure the safety and economy of the structure,the bridge is designed as a half-through/bowstring steel truss arch bridge that has a main span of 310 m,is hinged at two ends and features its two arch seats with different heights.This type of arch bridge is quite suitable to the bridge site,which bears small additional internal forces and is quite adaptive to the foundation displacement.To meet the load bearing requirements of the arch bridge with high and low arch seats and improve the manufacturing efficiency,the arch axis complies with an integral catenary,where the virtual calculated span length,rise and axis coefficient of the arch are 340 m,86.2 m and 1.7,respectively.The arch consists of two N lateral truss ribs that are distanced center-to-center at 27 m and connected by criss-cross lateral bracings and K lateral bracings.Each arch rib is composed of constant cross-section flat steel boxes,with integral bolting/welding modes.The deck consists of cellular steel girder and reinforced concrete slabs,which create clear load transfer paths.A minor span extends out from the end crossbeam at each side of the bridge to address the possible girder-end reaction forces in the side span,and a speed locker is installed at each deck end.Swing hinges are adopted at the arch springs to ease the load-bearing burden there under multiple loads and maximize the durability of the structure.The global and local finite element analyses indicate that the bridge has effective static and dynamic performance.