独塔地锚回转缆悬索桥设计关键技术

Key Design Techniques of a Single-Tower Earth-Anchored Suspension Bridge with Looping Cable Anchorage System

济新高速黄河三峡大桥为独塔地锚回转缆悬索桥,主缆跨度布置(540+185)m,垂跨比1/16,桥塔采用门形钢筋混凝土塔,北岸采用覆表式重力锚、南岸采用扩大基础重力锚,加劲梁采用钢桁梁、正交异性钢桥面板的板桁结合体系。单跨简支加劲梁一端固定、一端自由,横向设置抗风支座+限位剪断装置的约束体系。通过比选,回转缆索鞍系统采用了三索鞍体系,采用L形双滑动副底座系统以满足双向压力作用。主缆采用近六边形斜向非对称的索股编排方式,解决了回转端和塔顶主缆弯曲平面方向存在90°的转角差、索股扭曲交叉不易整形入鞍的问题。加劲梁节点设置钢牛腿和吊索连接,解决了回转缆立面展布空间需求问题。主缆采用优化后的PPWS法架设,钢桁梁采用缆索吊安装。

The Yellow River Three Gorges Bridge is a single-tower earth-anchored suspension bridge carrying a section of the Jiyuan-Xin′an Expressway.The tower is a portal-frame reinforced concrete structure.The main cables,which are arranged in two spans of 540 m and 185 m,creating a sag-to-span ratio of 1/16,are anchored by a shallow gravity anchorage on the north bank and by a spread-foundation-supported gravity anchorage on the south bank.The stiffening girder consists of steel trusses overlaid with orthotropic steel deck plates.The simply-supported span with hanger cables is fixed with the abutment on one end and leaves the other end live,where transverse wind-resistant bearings and restrainers are installed.A three-saddle system is selected,which is fitted with L-shaped double slipping sets to accommodate the two-way compressive forces.The main cables are of quasi-hexagonal cross-section,with asymmetrically-arranged steel strands to address a rotation angle difference of 90°against the bending plane and facilitate the placement of the twisted strands into the saddles.To spare enough room for the looping of the main cable,steel brackets are added at the nodes of the stiffening girder to connect with the hanger cables.The main cable was installed by the modified PPSW method,the steel trusses were installed by the cableway crane.