大跨度悬索桥施工阶段三维颤振精细化分析

Refined 3D flutter analysis of long-span suspension bridges under construction

悬索桥施工期结构柔性大,静风作用下结构大变形和刚度变化以及桥址区域内风速空间分布的非均匀性可能会对结构颤振稳定性构成不容忽视的影响。基于线性颤振分析方法,考虑结构非线性、静风效应和风速空间非均匀分布等因素建立了精细化的大跨度桥梁三维非线性颤振分析方法,并编制了相应的计算分析程序。以润扬长江大桥南汊悬索桥为工程背景,模拟加劲梁从跨中向两侧桥塔和由两侧桥塔向跨中对称拼装两种主梁架设顺序,分析了施工全过程悬索桥颤振稳定性的变化趋势,并探明了静风效应和风速空间分布非均匀性对施工状态悬索桥颤振稳定性的影响。分析结果表明:加劲梁采用从两侧桥塔向跨中对称架设时,悬索桥可以获得比较好的颤振稳定性,尤其在主梁架设初期;静风效应对施工过程悬索桥颤振稳定性的影响显著,特别是加劲梁架设初期(主梁拼装率约在40%以下);风速沿竖向高度变化和风速空间分布宽度对施工期悬索桥的颤振稳定性影响不大,但风速空间的非对称分布因素影响则比较显著;静风效应和风速空间非对称分布因素须在大跨度悬索桥施工期的颤振分析予以充分考虑。

Owing to the large slenderness,the remarkable structural deformation,and the variation of structural stiffness caused by the static wind action,the spatial non-uniformity of wind speed at the bridge site may have unnegligible influence on the flutter stability of long-span suspension bridges under construction.Based on the linear flutter analysis,a refined three-dimensional nonlinear flutter analysis method was proposed,in which the effects of the structural nonlinearity,the static wind action,and the spatial non-uniformity of wind speed were fully considered and the corresponding computational program was coded.With Runyang bridge over the Yangtze River taken as an example,the simulations of the girder segments erected symmetrically from the midspan to the two side towers and from the two side towers to the midspan were conducted,respectively,the evolution of flutter stability of the bridge during the deck erection was investigated numerically,and the effects of the static wind action and the wind speed spatial non-uniformity on the flutter stability of the suspension bridge at the construction phase were revealed.The results showed that,for a suspension bridge under construction,it is more stable aerodynamically as the girder segments are erected from the two side towers to the midspan.The static wind action has significant influence on the flutter stability of suspension bridges at the construction phase,especially at the early erection phases(the deck completion is generally below 40%).The flutter stability of suspension bridges at the construction phase is basically not influenced by the variation of wind speed along the vertical direction and the wind distribution width but significantly impacted by the spatial non-symmetric distribution of wind speed.The effects of the static wind action and the wind speed spatial non-symmetric distribution should be considered accurately in the flutter analysis of long-span suspension bridges under construction.