According to the analysis on the structural behavior of steel box girder (SBG) under eccentric load, the proper diaphragm layout of SBG should be investigated from the point of analyzing distortional warping stress. It is put forward that Beam on Elastic Supports Analogy (BESA) should be adopted to analyze the distortional warping stress of long-span variable cross-section SBG. The distortion of single-room rectangular box girder is regarded as the bending of the beam on elastic foundation (BEF) based on the similarity between the distortional warping control differential equation of the single-room rectangular box girder and the bending control differential equation of BEF. By this analogy method, the distortional warping stress of the single-room rectangular box girder influenced by diaphragm spacing and rigid can be solved. With the distortional warping stress of the controlled box girder less than 15 percent of bending normal stress as the target, the method is adopted to determine the proper diaphragm layout for Chongqi Main Bridge. If diaphragm spacing is 5. 6 m, solid-web diaphragm should be adopted on top of each pier, while truss-type diaphragms for others.%根据偏心荷载作用下钢箱梁的受力特点,从分析畸变翘曲应力的角度出发研究钢箱梁横隔板的合理布置.提出采用弹性支承连续梁比拟法分析大跨度变截面钢箱梁的畸变翘曲应力.根据单室矩形箱梁畸变控制微分方程与弹性地基梁弯曲控制微分方程的相似性,将单室矩形箱梁的畸变比拟成弹性支承连续梁的弯曲,据此求解考虑横隔板间距和刚度影响的单室矩形箱梁的畸变翘曲应力.以控制箱梁畸变翘曲应力不超过弯曲正应力15％为目标采用该方法确定崇启大桥横隔板的合理布置形式为:当横隔板间距设置为5.6m时,在各墩墩顶宜采用实腹式横隔板；在其他位置可采用桁架式横隔板.
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