磁流变阻尼器对斜拉索减振效果的试验研究

Experimental Study of Vibration Mitigation of Bridge Stay Cable Using MR Dampers

采用磁流变阻尼器作为被动控制器件 ,以钱江三桥南岸 15 4 m长的斜拉索为试验对象 ,通过阶跃激励的方法获得斜拉索振动的自由衰减信号。对采集到的信号进行小波分解、希尔伯特变换识别系统的等效阻尼比。据此来判断磁流变阻尼器在施加不同电压情况下对索前三阶模态振动的减振效果 ,并与油阻尼器的制振效果进行比较。试验结果表明磁流变阻尼器作为被动控制器件时制振效果明显 ,优于油阻尼器且控制的频域范围要比油阻尼器的广 ;当供电失效时也可满足索减振的要求。索的各阶共振峰频率在安装 MR阻尼器后发生稍许漂移。

Long-span cables are susceptible to vibration with large amplitude under wind/rain loading or support excitation. To overcome these problems, the full-scale experimental using Magnetorheological (MR) Dampers is carried out for mitigating cable vibration. The discrete MR dampers are installed on the 154 m-long cable near the anchorage in the 3rd Qianjiang cab le-stayed bridge. Vibration mitigation of the cable using MR dampers is experimentally in vestigated by a series of free vibration tests and compared to that of sing oil dampers. The displacement signal is driven by harmonic plannar loads, filtered through wavelet descomposation and transformed by Hilbert. The equivalent cable modal damping ratios attributed to MR dampers are measured, and the relationship between the equivalent modal damping ratios, the system frequency, the voltage imposed and displacement responses at the point of cable was pursued. It is shown that MR dampers to the cable can more significantly reduce cable vibration than oil dampers do. The resonant frquencies of the cable installed MR dampers have little change. There is optimum voltage on which the maximum modal damping ratio can be achieved.