Abstract: In order to meet the increasing traffic demand, in recent years, large-span cable-stayed bridges have begun to use separated double-sided steel box composite beams with large deck width, high lateral stiffness and good wind resistance. Taking the extra-wide separated double-sided steel box composite girder cable-stayed bridge with a girder width of 45.9m as the background project, a three-dimensional member system model and a refined segment model were established by using MIDAS and ANSYS respectively, to study the shear lag effect during the completion stage and construction process of the bridge. The influence of the steel main girder plate thickness on shear lag effect was also analyzed through the sensitivity analysis. The results indicate that in the completed bridge state, the variation range of shear lag coefficients at the bottom and top of the concrete slab is 2.152~2.762 and 1.262~2.024, respectively. The closer to the mid-span section, the greater the shear lag coefficient of the concrete slab. The concrete slab exhibits a significant positive shear lag effect at the position of webs and small stringers, while mainly shows a negative shear lag effect at the position of diaphragms. The shear lag effect at both ends of the concrete slab is most prominent due to the influence of the horizontal component force of the stay cable. During the construction, the shear lag coefficients of the bottom and top of the concrete slabs range from 3.978 to 4.188 and 1.186 to 1.301, respectively. It is necessary to focus on the shear lag effect at the bottom of the slab. The construction steps have a significant impact on the shear lag effect of the concrete slab in the composite girder, particularly the installation of the steel main girder. When the thickness of the steel main girder changes, the variation pattern of the shear lag coefficient is similar. It is recommended to use a thickness of 20~30 mm for the top plate and 15~20 mm for the bottom plate of the steel main girder.

Key words: bridge engineering; composite girder cable-stayed bridge; separated double-sided steel box composite girder; shear lag effect; finite element method; parameter analysis

摘要： 为了满足日益增长的交通量需求，近年来大跨度斜拉桥开始采用桥面宽度大、横向刚度高和抗风性能好的分离式双边钢箱组合梁。以梁宽为45.9 m的超宽分离式双边钢箱组合梁斜拉桥为背景工程，分别采用MIDAS和ANSYS建立三维杆系模型和节段精细化模型，研究其成桥阶段和施工过程中的剪力滞效应，并通过敏感性分析研究钢主梁板厚度对剪力滞效应的影响。结果表明：成桥状态下，混凝土板底和板顶的剪力滞系数变化范围分别为2.152~2.762和1.262~2.024，越靠近跨中节段，混凝土板的剪力滞系数越大。在边腹板、中腹板和小纵梁位置，混凝土板的正剪力滞效应显著，横隔梁顶的混凝土板则主要呈现负剪力滞效应。受到斜拉索水平分力的影响，混凝土板两端的剪力滞效应最突出。施工过程中混凝土板底和板顶的剪力滞系数范围分别为3.978~4.188和1.186~1.301，需要重点关注板底的剪力滞效应。施工步骤对组合梁混凝土板的剪力滞效应影响较大，尤其是钢主梁安装工况。钢主梁板厚变化时，剪力滞系数变化规律相似，建议钢主梁顶板厚度为20~30 mm，底板厚度为15~20 mm。

关键词: 桥梁工程； 组合梁斜拉桥；分离式双边钢箱组合梁；剪力滞效应；有限元法；参数分析