丹江口水库特大桥多格室钢-混结合段设计

Design of Latticed Steel-Concrete Joint Section of Danjiangkou Reservoir Bridge

丹江口水库特大桥为主跨760 m的双塔双索面部分地锚式混合梁斜拉桥,主跨主梁采用分离式双钢箱+正交异性钢-UHPC组合桥面结构轻型组合梁,边跨主梁采用PC边主梁。组合梁与PC梁连接过渡段总长6.0 m,其中钢梁段长1.0 m,钢梁加强段长3.0 m,钢-混结合段长2.0 m。为解决钢-混结合段边箱部分截面刚度过渡剧烈、应力集中明显、格室内填充混凝土施工困难等问题,利用外腹板和风嘴箱室构造边箱多格室断面,形成“钢格室+后承压板”的结构,提高钢-混结合段边箱部分截面刚度过渡均匀性;格室内钢-混连接区域采用开孔板剪力键和剪力钉,提高结合段的抗剪强度及延性,增强整体连接的可靠性;格室内填充料采用活性粉末混凝土,并综合考虑结构性能需求和技术指标进行配合比优化,改善结合段的耐久性和施工可靠性。结构受力分析结果表明,各构件受力均满足设计要求。

The Danjiangkou Reservoir Bridge is a two-pylon cable-stayed bridge with a main span of 760 m,featuring pairs of stay cables anchored to the ground.The stay cables are arranged in double cable planes.The superstructure in the main span consists of two lateral steel box girders connected by composite light deck panels of orthotropic steel plates and UHPC overlay.The superstructures in the side spans consist of two lateral PC box girders.The transition between the composite girders and the PC girders measures 6.0 m long,specifically a 1.0 m-long steel girder segment,a 3.0 m-long steel girder strengthening segment,and a 2.0 m-long steel-concrete joint segment.Against the exterior webs of the box girders and the cells of the wind vanes,a latticed section is created,with which a structure contains a steel latticed chamber and a rearing bearing plate is formed,aiming to allow the smooth stiffness transition between the steel and concrete box girders,alleviate stress concentration and facilitate the pouring of infill concrete in the latticed chamber.PBL connectors and shear studs are arranged for the connection of the steel and concrete components,to improve the shear strength and ductility of the joint section,and the reliability of the overall connection as well.The latticed chamber is filled with reactive powder concrete with a mix proportion optimized in accordance with the mechanical property of the structure and technical requirements,thereby enhancing the durability of the steel joint section and the construction reliability.The mechanical property analysis demonstrates that the load bearing performance of all the components meet the design requirements.