大跨度悬索桥施工阶段静风稳定性精细化分析

Refined aerostatic stability analysis of long-span suspension bridges under construction

大跨度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其静风稳定性造成影响。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静风分析方法,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例,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静风稳定性的变化趋势,并探明了风速空间分布非均匀性对成桥和施工状态悬索桥静风稳定性的影响。结果表明:加劲梁采用从两侧桥塔向跨中对称架设时,悬索桥可以获得较好的静风稳定性,尤其在施工初期;风速沿竖向高度变化和风速空间分布宽度对成桥和施工状态悬索桥的静风稳定性影响不大,但风速非对称分布因素影响则比较显著,须在分析中重视和考虑。

Due to the great slenderness,the remarkable structural deformation,and the variation in structural stiffness caused by the static wind action,the spatial non-uniformity of wind speed at the bridge site may have influence on the aerostatic stability of long-span suspension bridges under construction.A refined method of three-dimensional nonlinear aerostatic analysis is established and the corresponding computational procedure is programmed,in which the effects of structural nonlinearity,the static wind action,and the spatial non-uniformity of wind speed are fully considered.By taking Runyang bridge over the Yangtze River as an example and through simulating the girder segments erected symmetrically from the midspan to the two side towers and from the two side towers to the midspan,respectively,the evolution of aerostatic stability of the bridge during deck erection is investigated numerically and the effect of wind speed spatial non-uniformity on the aerostatic stability of suspension bridges under construction and in completion is evaluated.The results show that,as for suspension bridges under construction,it is more aerostatically stable as the girder segments are erected from the two side towers to the midspan.The aerostatic stability of suspension bridges under construction and in completion is seldomly influenced by the variation in wind speed along the vertical direction and the wind distribution width.However,it is significantly impacted by the spatial non-symmetric distribution of wind speed and therefore the factor should be considered accurately.