鹅公岩轨道大桥加劲梁施工过渡斜拉体系设计

Design of Transitional Cable-Stayed Bridge for Constructing Egongyan Rail Transit Bridge

鹅公岩轨道大桥为主跨600m的自锚式悬索桥,由于建设条件受限,该桥在悬索桥桥塔上固结钢塔,采用"先斜拉、后悬索"的方案施工。过渡斜拉桥是该自锚式悬索桥钢箱加劲梁施工的关键结构。根据悬索桥的结构布置、钢箱梁刚度特性和对不同固结钢塔高度的比较,确定了斜拉索的布置形式、最佳钢塔高度和相应的斜拉索规格选型。通过对过渡斜拉桥成桥过程和斜拉桥-悬索桥体系转换过程进行仿真分析,确定斜拉索及其锚固结构由过渡斜拉桥成桥过程最大索力控制设计,固结钢塔由斜拉桥-悬索桥体系转换过程控制设计,并以此为依据对过渡斜拉体系主要构件进行设计。斜拉索采用1 670MPa7mm预制平行钢丝索;钢塔高42.5m,采用双肢结构,每肢均为5.6m×3.0m矩形钢箱。实践表明:过渡斜拉体系设计合理,顺利地辅助完成了钢箱梁的架设及斜拉桥-悬索桥体系的转换。

The Egongyan Rail Transit Bridge is a self-anchored suspension bridge with a main span of 600 m.Due to limitations at the construction site,a construction scheme of installing the cable-stayed structure prior to the erection of the suspended structure was implemented,with steel pylons fixed to the towers of the suspension bridge.The transitional cable-stayed bridge is a key structure in the erection of steel box girders for the self-anchored suspension bridge.The configuration of the stay cables,ideal height of the steel pylons and the scale of the stay cables were determined by referring to the structural configuration of the suspension bridge,rigidity of the steel box girders and the comparison of different pylon heights.The forming process of the transitional cable-stayed bridge and the process of transformation from a cable-stayed bridge to a suspension bridge were simulated and analyzed.The results show that the maximum cable force in the forming process of the transitional cable-stayed bridge dominates the design of stay cables and the anchorage structure,and the systematic transformation from a cable-stayed bridge to a suspension bridge governs the design of the steel anchor pylon,based on these,the main components of the transitional cable-stayed bridge are designed.The stay cables consist of the7 mm prefabricated parallel steel wires,each with a tensile strength of 1 670 MPa.The steel pylon,42.5 min height,has two legs,each with rectangular steel box cross-section measuring 5.6 m×3.0 m.The engineering practice proves that the design of the transitional cable-stayed bridge is rational,which can ease the erection of the steel box girders and the systematic transformation from a cable-stayed bridge to a suspension bridge.