交叉吊索对超大跨CFRP主缆悬索桥颤振性能的改善作用

Improvement of flutter stability of super long span suspension bridge with CFRP cable by crossed hangers

颤振一旦发生,将给桥梁结构带来毁灭性灾难,颤振稳定性是大跨桥梁重要的抗风控制指标。交叉吊索可显著提高超大跨悬索桥的扭转刚度,从而提高其颤振性能。该文以某主跨3500m的超大跨径CFRP(carbon fiber reinforced plastics)主缆悬索桥为工程背景,从频率和振型两方面分析了水平交叉吊索和竖向交叉吊索对其动力特性的影响,并绘制与颤振相关的弯频和扭频随交叉吊索设置位置的变化曲线(简称"影响曲线"),进而针对提高结构颤振稳定性提出11种交叉吊索设置方案。基于耦合颤振的分步分析法,分析这11种方案的颤振稳定性。分析结果表明,在中跨满布水平交叉吊索的同时,在中跨L/3和边跨跨中各对称设置一对竖向交叉吊索,结构的颤振稳定性最好,颤振临界风速提高达49%。

Flutter is rather destructive to bridges, so the flutter stability is one of the most important wind-resistant behaviors. The torsional stiffness and flutter stability of super long span suspension bridges can be enhanced significantly by cross hangers. In this paper, the influences of two kinds of cross hangers on the dynamic property of a super large span suspension bridge with a 3500m span and CFRP （carbon fiber reinforced plastics） cables were studied from the point of frequencies and natural vibration shapes. The influence curves of fundamental frequency of vertical bending and torsion versus the position of cross hangers were obtained. According to the influence curves, 11 arrangement plans of cross hangers were proposed. Step-by-step method was used to analyze the flutter stability of the 11 plans. The results show that connecting the two cables in the total length of main span using horizontal cross hangers and setting up vertical cross hangers between cable and girder at 1/3 of main span and middle of side span can improve the flutter stability of super long span suspension bridge dramatically and the critical flutter velocity is improved by 49%.