MR阻尼器对斜拉索共振峰频率漂移的影响

本文采用Spencer提出的MR模型,对斜拉索和MR阻尼器组成的系统进行了动力分析,考察了MR阻尼器型号、安装位置、施加的电压以及斜拉索基频(张力、索长、质量)、激励荷载(类型、频率、大小)等各种因素对斜拉索共振峰频率漂移的影响。进而对钱江三桥南岸154m长的斜拉索进行了现场试验。斜拉索自由振动的衰减信号通过阶跃激励的方法获得,经小波变换、Hilbert变换识别出系统的共振峰频率,并与斜拉索在安装油阻尼器和无阻尼器两种情况进行了比较。计算了杭州湾大桥330m长的索在被动控制、半主动控制下的各阶共振峰频率。研究表明,斜拉索在安装MR阻尼器后共振峰频率略微增大。其影响程度比安装油阻尼器时要大。因此MR阻尼器的制振效果除主要来自耗能外,还有部分来自调频作用。

Resonant frequency shift of stay-cable influenced by using MR dampers

The dynamic response performances of a cable with MR dampers are explored in detail using Spencer photometric model.Some factors such as MR dampers(marker,mounting position and voltage applied),the first frequency of cables(tensile force,length and mass per unit length),exciting loads(type,frequency and amount) having influence upon resonant frequency shift of stay-cable are discussed.The discrete MR dampers were installed on the 154m-long cable near the anchorage in the 3rd Qianjiang cable-stayed bridge.Vibration mitigation of the cable using MR dampers in a purely passive mode,where constant levels of current are supplied to the damper,is examined by a series of free vibration tests and compared to that of using oil dampers.The displacement signal is driven by harmonic planar loads,filtered through wavelet decomposition and transformed by Hilbert.The relationship between the system frequency,the voltage imposed and displacement responses at the point of cable was pursued.Then the 330m length cable in the Hangzhou Bay Bridge using passive and semiactive control was calculated.It is shown that frequency shift attributed to MR dampers has a little change and is higher than oil dampers do.So the method installed MR dampers can be achieved not only consuming energy dissipation but also tuned frequencies of the cable.