随机减量法在斜拉桥拉索模态参数识别中的应用

APPLICATION OF RANDOM DECREMENT TECHNIQUE TO MODAL PARAMETER IDENTIFICATION OF CABLES FOR A CABLE-STAYED BRIDGE

斜拉桥拉索模态参数 (固有频率、阻尼比 )在索力测试、拉索减振、实时控制等方面起着重要作用。文中利用随机减量技术从岳阳洞庭桥环境激励下拾取的拉索的加速度响应中分离出自由衰减振动加速度响应信号 ,将获取的加速度响应信号表达为一理论形式 ,综合运用参数识别、最优估计理论 ,识别出拉索的模态参数 ,与理论值吻合良好。本文方法简单 ,试验容易实施 ,具有工程实用价值。

Modal parameters of a cable for a cable-stayed bridge, such as natural frequencies and damping ratios, play an important role in measuring cable tension forces, controlling the bridge vibration and mitigating cable vibration. By using the random decrement technique (RDT), acceleration response signals of free vibration are separated from those responses obtained by ambient excitation (also called impulse excitation) to Dongtinghu Bridge in Yueyang, Hunan province. The free vibration signals are then expressed as a theoretical form in which parameters of the cable are included. In addition, parameter identification theories and optimum estimate theories are used simultaneously in obtaining modal parameters of the cable. The method proposed in this paper is simple and the structural experiment is easy to complete. It is obviously practical in engineering. Digital simulation and practical testing show that the presented method is effective and applicable.