南非姆斯卡巴河桥总体设计

Overall Design of Msikaba River Bridge in South Africa

南非姆斯卡巴河桥跨越姆斯卡巴大峡谷,为主跨580 m的单跨全地锚式斜拉桥。根据桥位地形特点,主梁仅在主跨内设置,为混凝土肋板梁+双边箱形组合梁的混合梁结构,双边箱梁通过桁架式横梁连接,现浇混凝土桥面板通过剪力钉与钢主梁连接,跨中设置剪力铰。17对钢绞线斜拉索在主跨内采用双索面半扇形布置,背索呈竖琴式布置,斜拉索通过钢锚梁、钢锚箱和混凝土齿块分别锚固于桥塔、主梁和锚碇上,锚固背索的锚碇为重力式预应力混凝土结构。桥塔为倒Y形结构,采用混凝土扩大基础,扩大基础间浇筑施加横向预应力的混凝土板,并与主梁固结。根据桥梁结构特点和现场地理条件,混凝土肋板梁采用支架现浇法施工,组合梁采用悬臂拼装法施工。

The Msikaba River Bridge in South Africa,spanning across the gorge created by the Msikaba River,is an earth-anchored cable-stayed bridge.To accommodate the site condition,the cable-stayed bridge only has one span with a tower to tower distance of 580 m.The superstructure consists of the concrete ribbed beams and the double-edge-box beams that are connected by the truss cross frames.The cast-in-situ concrete slabs are connected with the steel beams via shear studs,and shear hinges are set in the midpan.17 pairs of stay cables comprising steel strands are fanned out in double cable planes in the main span,and the back stays are in harp planes.The stay cables are anchored to the towers,main beams and anchor blocks by steel anchor beams,steel anchor boxes and concrete wedges,respectively.The anchor blocks where the back stays are anchored are gravity prestressed concrete structures.The towers are inverted Y-shaped structures supported by concrete spread foundations.Transversely-prestressed concrete slabs were cast between the spread foundations and fixed with the main beams.To suit the structural characteristics of the bridge and the geological condition at the site,the concrete ribbed beams were cast in-situ on scaffoldings,and the steel edge box beams and truss cross frames were erected by cantilever assembly method.