The Dongting Lake Bridge is a cable-stayed bridge crossing the Dongting Lake where it meets the Yangtze River in southern central China. After this bridge was completed in 1999, its cables were observed to be sensitive to rain-windinduced vibration, especially under adverse weather conditions of both rain and wind. To investigate the possibility of using MR damping systems to reduce cable vibration, a joint project between the Central South University of China and the Hong Kong Polytechnic University was conducted. Based on the promising research results, the bridge authority decided to install MR damping systems on the longest 156 stay cables. The installation started in July 2001 and finished in June 2002, making it the world's first application of MR dampers on cable-stayed bridge to suppress the rain-windinduced cable vibration. As a visible and permanent aspect of the bridge, the MR damping system must be aesthetically pleasing, reliable, durable, easy to maintain, as well as effective in vibration mitigation. Substantial work was done to meet these requirements. This paper describes the implementation of MR damping systems for cable vibration reduction.

提出一种新的由结构振动响应识别结构阻尼比的方法。对于单自由度振动系统，推导出响应历程与时轴所围各面积之间的确定性关系后，利用各面积之间的关系来确定自由衰减振动的阻尼比系数。与传统的对数衰减率法比较，它具有抗噪声干扰能力强、精度高、稳定性好及简便实用等特点。对于多自由度振动系统，先将结构上某测点的自由振动响应表达为一理论解析式x（t)，以eat相乘x（t），预给a初值范围，通过牛顿二分法（或黄金分割法）搜索a值，直至eatx（t）做等幅振荡，则该阶模态的各模参数得以确定。从总响应中扣除该阶模态对总响应的贡献后，重复这一过程，则可识别出响应信号中各阶模态的模态阻尼比。仿真计算与岳阳沿庭湖斜拉桥拉索实测试验结果表明了本文方法的有效性和实用性。

利用我们开发的国内第一个强迫振动法试验方法，研究了三种不同断面的桥梁颤振自激力特性和Scanlan提出的颤振导数理论的若干假定。研究表明，在实用风速范围内，颤振导数基本与测试频率、振幅无关；流线断面的自激力能基本符合Scanlan的线性假定，但钝体断面的自激力高次谐波分量大，明显具有对模型运动的非线性响应特征。

提出了一种在AN SYS中实现颤振时程分析的有限元模型和分析方法。该模型采用MA2TR IX27单元来模拟桥面主梁受到的自激力，依据刚度和阻尼等效的原则, 推导了该单元的刚度矩阵、阻尼矩阵与颤振导数之间的关系，然后对整个系统的运动方程进行数值积分来确定系统的响应，通过位移时程曲线来判断结构的颤振稳定性。最后，以一简支梁为例介绍了在ANSYS中颤振时程分析实现的过程，其分析结果与精确解、频域分析结果吻合很好。

采用磁流变（MR）阻尼器对我国第一座三塔斜拉桥——湖南岳阳洞庭湖大桥斜拉索的减振问题进行了试验研究。内容包括：（1）设计试验装置；（2）不装阻尼器的斜拉索自由振动试验；（3）装有MR阻尼器的斜拉索自由振动试验。试验结果表明，安装MR阻尼器可显著提高斜拉索的模态阻尼比。通过模态阻尼比随MR阻尼器外加电压变化的关系，可得出拉索等效模态阻尼比的优化值，为实现拉索的有效减振提供了科学依据。