中文摘要：

学习 girder 和方法的僵硬分发到留下来电缆线的桥牌的 identifymodal 参数，横梁建模的简化动态有限元素方法模型 namedthree 与两倍肋骨为 girder 被建立。基于简化 modelfour 僵硬公式根据哈密尔顿的意见被推出原则。这些公式分别地反映曲折、砍的、免费扭转和限制扭转变丑的 wellthe 贡献。关于形式的参数的一个鉴定方法被联合方法 ofpeak 价值和力量提出光谱密度根据在周围的刺激下面的形式的测试。dynamicfinite 元素方法分析和形式的测试在长跨度的具体 cable-stayedbridge 被执行。在理论分析和 testresults 之间的频率的错误主要是不到10%的结果表演，和为留下来电缆线的 bridgeare 的最重要的形式的参数决定是纵的漂浮模式，第一个垂直曲折模式和 firsttorsional 模式，它证明为三根横梁的僵硬分发的方法为 isaccurate 和方法建模识别形式的参数在周围的刺激下面是有效的形式的测试。

英文摘要：

To study the stiffness distribution of girder and the method to identify modal parameters of cable-stayed bridge, a simplified dynamical finite element method model named three beams model was established for the girder with double ribs. Based on the simplified model four stiffness formulae were deduced according to Hamilton principle. These formulae reflect well the contribution of the flexural, shearing, free torsion and restricted torsion deformation, respectively. An identification method about modal parameters was put forward by combining method of peak value and power spectral density according to modal test under ambient excitation. The dynamic finite element method analysis and modal test were carried out in a long-span concrete cable-stayed bridge. The results show that the errors of frequencies between theoretical analysis and test results are less than 10% mostly, and the most important modal parameters for cable-stayed bridge are determined to be the longitudinal floating mode, the first vertical flexural mode and the first torsional mode, which demonstrate that the method of stiffness distribution for three beams model is accurate and method to identify modal parameters is effective under ambient excitation modal test.