基于环境激励的大跨度双主肋混凝土斜拉桥模态的优化识别研究

OPTIMAL IDENTIFICATION OF MODAL PARAMETERS OF LONG-SPAN CABLE-STAYED BRIDGE WITH DOUBLE-RIBS GIRDER BASED ON AMBIENT EXCITATION

研究双主肋混凝土主梁采用“三主梁”模型的约束扭转刚度的分配原则和方法。通过研究斜拉桥模态试验的特点,首次提出了在两点移动测点法的基础上,利用梁模型振型函数优化峰值拾取法的模态参数,取得了理想的效果。整桥模态实验结果与计算结果比较表明对双主肋混凝土斜拉桥的动力模型刚度分析准确,振型函数优化识别法是可行的。

To establish dynamic FEM model of cable-stayed bridge with double-ribs girder, the dynamic stiffness distribution rules and methods of “three main girders” model are studied, which relate to flexural rigidity, shearing rigidity, free torsion rigidity and restricted torsion rigidity. Based on the former work, dynamic FEM analysis is made on the dynamic properties of the longest-span concrete cable-stayed bridge in Asia with geometric nonlinear effects considered. On the base of modal test of cable-stayed bridge, applying two points method under ambient excitation, a method to identify modal parameters is put forward, which takes advantage of girder vibration mode functions to optimize modal parameters derived by peak picking method. Comparing the results of dynamic FEM analysis with that of modal test, the resulted modal frequencies and modal shapes are considerably consistent, and it demonstrates that the analysis of distributed stiffness of “three main girders” dynamic FEM model is accurate and the method of vibration mode function optimal identification is effective.