大跨度双层桁架梁悬索桥颤振性能试验研究

Experimental Study on Flutter Performance of Long-Span Suspension Bridge with Double-Deck Truss Girder

为提高大跨度双层桁架梁悬索桥的颤振性能,以主跨为1700 m的杨泗港长江大桥为工程背景,通过节段模型风洞试验,分别研究了上中央稳定板、下稳定板、水平翼板以及组合措施对主梁颤振性能的影响,并通过将有效气动措施与主梁原有构件相结合的方法来减小传统气动措施带来的不利影响,针对最优气动方案,研究了阻尼比对主梁颤振性能的影响.研究结果表明:原主梁断面在0°和+3°攻角下发生了没有明显发散点的单自由度扭转软颤振,颤振临界风速分别为50.5 m/s和31.2 m/s;安装于上层桥面的上中央稳定板、下层桥面的下稳定板以及与人行道底部齐平的水平翼板均能不同程度地提高主梁的颤振稳定性;当把水平翼板与下层桥面的下稳定板组合后,主梁的颤振临界风速增长率可高达34%,在此基础上提出了将上层托架和人行道板加宽、并将下稳定板和检修车轨道相结合的最优气动方案;当扭转阻尼比由0.37%增加至0.52%时,主梁的颤振临界风速可提高11.9%,说明阻尼器可能对发生单自由度扭转软颤振的桥梁起到良好的抑振效果.

In order to improve the flutter performance of a long-span suspension bridge with a double-deck truss girder,the Yangsigang Yangtze River Bridge with a main span of 1700 m was taken as the engineering prototype to conduct section model wind tunnel tests,to study the effects of the upper central stabilizers,lower stabilizers,horizontal flaps and their combinations on the flutter performance of the bridge girder.Then,the effective aerodynamic measures were combined with the truss girder components to reduce the adverse effects of traditional aerodynamic measures.Finally,for the optimal aerodynamic scheme,the influence of damping ratio on the flutter performance of the optimized bridge girder was investigated.The results show that the singledegree-of-freedom torsional soft flutter with no evident divergent point has occurred to the bridge girder in the original design at attack angles of 0°and+3°,and the corresponding critical flutter wind speeds are 50.5 m/s and 31.2 m/s,respectively.The upper central stabilizers installed on the upper deck,the lower stabilizers installed below the lower deck,and the horizontal flaps installed at the level of the bottom of sidewalk can improve the flutter performance of the double-deck truss girder to varying degrees.The critical flutter wind speed of the main girder can be increased by over 34%by combining the horizontal flaps and lower stabilizers installed at the lower deck.On this basis,an optimal aerodynamic scheme is proposed to broaden the upper bracket and sidewalk plate,and combine the lower stabilizer with the track of the maintenance vehicle.Meanwhile,it is found that the critical flutter wind speed of the main girder can increase by 11.9%when the system torsional damping ratio increases from 0.37%to 0.52%.This indicates that the dampers may be efficient in suppressing the soft flutter of bridges with single-degree-of-freedom torsional vibrations.