（1.兰州交通大学土木工程学院，甘肃 兰州 730070； 2.西北民族大学土木工程学院，甘肃 兰州 730030）
摘 要：西宁文汇桥为主跨158 m双塔混凝土自锚式悬索桥，采用“先梁后缆”法施工，加劲梁采用逐节段支架现浇法施工。该桥加劲梁体系转换原方案为三轮吊索张拉，由于原方案施工周期长、施工措施费用高，提出将原方案优化为两轮吊索张拉（优化方案）。为分析优化方案的优化效果，采用MIDAS Civil软件建立全桥有限元模型，分析优化前、后2种体系转换方案的结构内力和变形。结果表明：与原方案相比，优化方案在第1轮吊索张拉时，吊索的竖向位移均在控制界限范围内，无需临时接长，可节省施工成本；主缆和索鞍间的抗滑移安全系数和桥塔应力均变化平稳，简化了计算分析过程；优化方案可以减少一轮吊索张拉，并在缆索架设阶段进行部分二期恒载施工，提高了施工效率。
中图分类号： U448.25；U443.38 文献标志码： A
Optimization of System Transformation Schemes for Stiffening Girder of Wenhui Bridge in Xining
LU Wei1,2, YANG Zi-jiang1, LIU Shi-zhong1, HUANG Hong-meng1,2, GU Hao-wei2
(1. School of Civil Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China; 2. School of Civil Engineering, Northwest Minzu University, Lanzhou 730030, China)
Abstract: The Wenhui Bridge in Xining is a two-tower self-anchored concrete suspension bridge with a main span of 158 m. The stiffening girder was cast in situ on scaffoldings segment by segment, prior to the erection of the main cables. In the original scheme, the stiffening girder would experience system transformation along with three rounds of hanger cable tensioning. However, this scheme would result in long construction time and cost-demanding construction mea-sures, which was consequently optimized to be a two-round hanger cable tensioning scheme. To check the scheme optimization effect, the software MIDAS Civil was used to build the finite element model of the overall bridge, to analyze the internal forces and deformation of the structure in the contexts of the two schemes before and after the optimization. The results show that compared with the original scheme, the vertical displacements of hanger cables in the optimized scheme were all within the required control range during the first-round hanger cable tensioning , the hanger cables did not need to be temporarily lengthened, thus relatively more cost-saving. The safety factor for slippage between main cables and saddles as well as stresses in towers went through even variation, leading to the simplification of calculation and analysis. The optimized scheme cut off one-round of hanger cable tensioning and allowed the parallel construction of part of secondary dead loads in the cable erection stage, as a result, the construction efficiency was improved.
Key words: self-anchored suspension bridge; stiffening girder; system transformation; hanger cable tensioning; scheme optimization; finite element method