斜拉桥主梁振动对拉索阻尼器减振效果的影响分析

EFFECT OF GIRDER VIBRATION ON PERFORMANCE OF CABLE DAMPER FOR CABLE-STAYED BRIDGE

采用拉索索端阻尼器是大跨度斜拉桥拉索减振的主要措施之一。现有拉索阻尼器设计理论均假定索的两端为固结;然而,随着斜拉桥跨度的增大,桥梁结构整体刚度下降,主梁振动对拉索附加阻尼器减振效果的影响成为大跨度斜拉桥拉索减振设计需要考虑的问题。该文建立了索、梁和阻尼器组合系统的简化理论模型,并对其进行了复模态分析。以跨径分别为400m、650m和1km的3座斜拉桥主跨最长索为算例,分析了主梁振动对拉索附加阻尼器减振效果的影响,指出了现有阻尼器设计理论的不足。分析结果表明:主梁振动降低了拉索附加阻尼器的减振效果;在大跨度斜拉桥拉索的减振设计中,必须考虑主梁参与振动的影响。

One of the most effective measures for the vibration mitigation of long stay cables of large span cable stayed bridges is using mechanical dampers. In the conventional design theory for the cable damper, it is assumed that the ends of cables are fixed. However, when the span of the cable-stayed bridge becomes large and the structure becomes more flexible, the effect of the girder vibration on the cable damper performance may have to be considered. In this paper, a simplified theoretical model with cable, damper and girder is analyzed by a complex mode method. The longest cables of three cable-stayed bridges, with a span of 400m, 650m and 1000m respectively, were simulated to show the effects of the girder vibration. The analyzed results show that the girder vibration reduces the effectiveness of the damper as the cable length increases. Therefore, it is suggested that the girder vibration should be taken into account in the cable damper design for long span cable-stayed bridges.