棋盘洲长江公路大桥主桥总体设计

Overall Design of Main Bridge of Qipanzhou Changjiang River Highway Bridge

综合考虑防洪、通航、港口等建设条件限制,棋盘洲长江公路大桥主桥采用主跨1038 m的单跨钢箱梁悬索桥,一跨跨越长江。该桥加劲梁采用扁平流线型钢箱梁;桥塔采用门形混凝土塔,桥塔基础采用分离式承台+大直径群桩;南、北重力式锚碇分别采用圆形地下连续墙基础和扩大基础,锚碇锚固系统采用无粘结预应力锚固系统;主缆采用标准抗拉强度1860 MPa的预制平行钢丝索股(PPWS法施工),吊索采用标准抗拉强度1670 MPa的平行钢丝索股(PWS法施工)外套双层PE防护。设计过程中通过研究地下连续墙重力式复合锚碇基础受力特点和渗流规律,优化了南锚碇工程规模;提出基于频遇组合确定主梁纵向挡块间隙量的计算方法,有效减小了伸缩装置规格;分析正交异性钢桥面板疲劳性能影响因素并进行优化设计,提升了桥面板综合性能。

The Qipanzhou Changjiang River Highway Bridge was required to cross the Changjiang River without setting river piers,due to the comprehensive consideration of the flood control and navigation requirements as well as the nearby port.The selected option is a suspension bridge with a main span of 1038 m,and only the main span is suspended with hanger cables.The stiffening girder consists of flat streamlined steel boxes.The two towers are portal-framed concrete structures that are supported by large-diameter group pile foundations,and each tower leg is mounted on its independent pile cap.The south and north gravity-type anchorages are supported by a circular diaphragm wall foundation and a spread foundation,respectively.Inside the anchorages,the splayed strands are anchored via unbounded prestressing tendons.The main cables and hanger cables all consist of prefabricated parallel wire strands,with normal tensile strength of 1860 MPa and 1670 MPa,respectively,and the hanger cables are protected by double-layer PE sheaths.The engineering scale of the south anchorage was modified based on the research of the load bearing behavior of the combined diaphragm wall and gravity-type anchorage foundation and seepage flow.A method premised on frequently-encountered load domain combination to calculate the intervals of longitudinal stoppers in the stiffening girder is proposed,which can result in the reduction of the dimension of the expansion joints.The influential factors of the orthotropic steel deck plates are analyzed,based on which the structural details of the orthotropic steel deck plates are optimized and the integral performance of the deck is improved.