【摘要】 大跨度斜拉桥是一种在风力作用下易发生变形和振动的柔性结构,其施工阶段结构抗风性能比成桥状态有所降低。采用数值模拟方法系统研究了大跨度斜拉桥单、双悬臂两大施工过程结构抗风性能的变化规律,包括结构动力特性及风致抖振响应。结果表明,随着单悬臂长度的增长,侧弯、扭转基频不断下降,侧弯基频降速较快,竖弯基频则在250m悬臂长度内呈现一个上升区段;随着双悬臂长度的增加,侧弯基频下降最快,竖弯和扭转基频下降速度呈现先变快后减慢的规律。当单悬臂长度在300m悬臂范围内,悬臂端部竖向抖振响应随悬臂长度基本呈线性增长;侧向抖振位移在200m悬臂长度范围内基本呈线性增长,超过200 m之后,增速明显加快。当双悬臂长度在200m范围以内,抖振位移基本呈线性缓慢增长,当超过200m后,竖向抖振位移急剧增长,侧向位移增长速度亦加快,此时需充分考虑结构抖振响应对施工安全的影响。单悬臂端部抖振响应由主梁一阶模态起主要贡献,二阶模态亦有重要参与;双悬臂则以二阶振型,即对称振型起主要贡献。更多还原

【Abstract】 A long span cable-stayed bridge is a kind of flexible structure sensitive to wind effects,especially,during construction.Its wind-resistant behavior during two types of construction process including single-cantilever and double-cantilever was studied via numerical methods.The results showed that the lateral bending and torsional fundamental frequencies decrease with increase in the single-cantilever length,while the vertical bending one has a rising tendency until the cantilever length reaches 250m;with increase in the double-cantilever length,all the three fundamental frequencies decrease,the lateral bending one decreases most quickly;moreover,the vertical buffeting response increases linearly within the single-cantilever length of 300m;the same law appears for the lateral bending one until the singlecantilever length reaches 200m,when it is larger than 200m,the lateral buffeting response increases obviously;for double-cantilever construction,within the cantilever length of 200 m the buffeting response is rising linearly and slowly;the buffeting responses of single-cantilever construction are generally contributed by the first vibration mode of the girder and significantly influenced by the second mode;for those of double-cantilever construction,however,the symmetric vibration modes contribute more to the buffeting responses.更多还原