北盘江特大桥施工临时扣索索力优化研究

Study of Optimization of Temporary Fastening Stay Force during the Construction of Beipan River Bridge

北盘江特大桥为主跨290m预应力混凝土空腹式连续刚构桥,空腹区采用倾斜挂篮及支架现浇法施工,并设置下弦临时扣索以承担自重及施工荷载。为指导临时扣索张拉,基于结构预张力最大安全度设计理论,采用线性规划的优化算法和有限元法优化临时扣索索力。首先采用梁或三维桥梁模型的有限元法计算应力、弯矩或变形相对应的影响矩阵,然后将施工阶段各种控制条件转化为优化问题中线性的约束方程,以结构最大安全度为目标函数,借助ANSYS和MATLAB工具包实现结构施工状态下临时扣索索力的优化。计算结果表明,将该优化可行解作为设计中进行分析计算的索力初始值,对快速获得索力的设计值起到了指导作用,实际施工采用设计值,实桥施工效果良好。

The Beipan River Bridge is a prestressed concrete open-web continuous rigid-frame bridge with a main span of 290 m. The open-web region was cast in situ using inclined form travel- ers and scaffoldings, and the temporary fastening stays to the bottom chord were installed to bear the dead weight and the construction loads. To direct the tensioning of the temporary fastening stays, the forces of the temporary fastening stays were optimized following the theory of maximum safety design of pre-tensioning forces of the structure and by applying the optimization algorithm of linear programming and the finite element method. First of all, the finite element method of beam or three-dimensional bridge model to calculate the influence matrix corresponding with stress, ben- ding moment or deformation, then, various control conditions in the construction process were converted to the linear constraint equation in an optimization problem, taking the maximum safety of the structure as the objective function and using the ANSYS and MATLAB tools to realize the optimization of the forces of temporary fastening stays under the structural construction condition. The results of the calculation demonstrated that using the feasible solutions of the optimization as the initial values of the stay forces in the analytical calculation in the design could facilitate the ob- taining of the design values of the stay forces. In the practical construction, the design values were adopted, and the construction of the real bridge achieved good effect.