重庆两江大桥上层桥面结构设计研究

Design and Study of Upper Deck Structures of Twin River Bridges in Chongqing

重庆两江大桥由2座双层桥面的单索面双桁片主梁公轨两用斜拉桥组成,上层桥面均由正交异性梁板单元、上弦杆和中纵梁构成,与主桁形成板桁结合式构造。为使结构性能更优,通过分析上层锚索区桥面受力特性,对索梁锚固构造、桥面板纵肋形式、纵肋穿过横隔板开孔形式、桥面板工地连接接头等关键构造进行研究。结果表明:索梁锚固采用钢锚箱,构造简单、受力简捷明确;锚索横梁采用箱形截面具有很大的双向抗弯刚度,能有效控制面内和面外变形;桥面板纵肋采用开口板肋,可降低纵肋与盖板焊缝产生疲劳裂纹的概率;纵肋穿过横隔板开孔采用苹果形,应力分布和疲劳性能最优;双向荷载作用下锚索区桥面板、纵肋和横隔板交叉细节的抗疲劳性能有足够的安全保证。

The Twin River Bridges in Chongqing include two road‐cum‐light rail cable‐stayed bridges respectively having the double decks ,a single cable plane and a double‐truss main girder . The upper decks of the bridges are all made up of the orthotropic beam and plate units ,upper chords and the middle longitudinal beams and together with the main trusses there ,the plate and truss composite structures are formed .To make the structural performance of the bridges more op‐timal ,the critical structural details of the stay cable anchorages in the main girders ,the types of the longitudinal ribs of the deck plates ,the types of the openings in the diaphragms w here the lon‐gitudinal ribs pass through and the filed joints of the deck plates have been studied based on the a‐nalysis of the force characteristics of the upper decks in the stay cable anchorage zones .T he results of the study show that w hen the steel anchor boxes are used for the stay cable anchorages in the main girders ,the anchorages will be structurally simple and the force conditions of the anchorages will be direct and clear .When the cross beams for anchoring of the stay cables are designed into the box sections ,the cross beams will have very strong bidirectional bending stiffness and can ef‐fectively control the in‐plane and out‐of plane deformation .When the open ribs are used as the lon‐gitudinal ribs ,the open ribs can decrease the fatigue crack probability in the welded joints of the longitudinal ribs and deck plates .When the openings in the diaphragms w here the longitudinal ribs pass through are designed in the apple shape ,the stress distribution and fatigue performance will be the most optimal .Under the action of the dual loads ,the fatigue performance of the deck plates and the cross joint details of the longitudinal ribs and diaphragms in the cable anchorage zones will have adequate safety assurance .