Abstract: Based on the dimensional theory method，the theory of shearing force flows and Prandtl'S soapfilm analogy method，formulas for calculating torsional an gle and shearing force of box beam 6f anisomerous variable section at the stage of the balanced eantilever construction were inferred．By means of the formulas ，the torsion，distortion and internal force of the box beam of Chongqing Yudong Changjiang Bridge at the stage of balanced cantilever were calculated and analysed．The calctdationval result validates that the torque which is produced because the dead load and the constructing load distribute anisomerously has few torsion an d distortion on the box beam，and that internal force on the box beam is in the controllable area．

Key words: continual rigid frame bridge, the balan ced can tilever construction, anisomerous variable section, torsion and distortion of box beam

摘要： 采用空间理论方法、剪力流理论及Prandtl的薄膜比拟法，推导出了不对称箱型变截面梁悬臂施工扭转角度和 剪力计算公式．并用该公式对重庆鱼洞长江大桥在悬臂施工阶段箱梁扭转变形及受力进行了计算分析．计算结果证 实了。在施工阶段因恒载和施工荷载的不对称分布产生的扭矩对主箱梁的扭转变形影响不大，箱粱所受到的内力在 施工控制许容范围内．

关键词: 连续刚构桥, 悬臂施工, 不对称变截面, 箱粱扭转变形