A finite-element-based framework for buffeting analysis of long-span cable-supported bridges under skew winds is developed in the frequency domain utilizing the linear quasi-steady theory and the strip theory of aerodynamics in conjunction with the pseudo excitation method. A set of universal expressions for six components of buffeting forces is first derived in association with oblique cross-sections of bridge components, in which the buffeting forces are formed with respect to the wind coordinate system and then converted to those with respect to the structural coordinate system. Skew mean wind and three orthogonal components of velocity fluctuations can thus be easily handled without any further decomposition. The coherence between velocity fluctuations of wind turbulence at any two arbitrary spatial points is considered in the global wind coordinate system rather than in the global structural coordinate system. Aeroelastic stiffness and damping matrices due to self-excited forces are then taken into consideration in terms of the 18 flutter derivatives with respect to the oblique cross-sections. The pseudo-excitation method is finally employed to solve efficiently the fully coupled 3D buffeting problem of long-span cable-supported bridges under skew winds with the effects of multi-modes and spatial modes, inter-mode coupling and aerodynamic coupling, and the interaction among major bridge components being naturally included.

In the modal analysis of cable-stayed bridges using the finite element approach, the single-girder model or the double-girder model is often adopted for modeling the bridge deck. These two models are simple and easy to embody in commercial software packages, but the warping stiffness (constant) of bridge deck cannot be properly taken into consideration. This paper thus presents a triple-girder model consisting of one central girder and two side girders symmetrically connected to each other by transverse links. The proposed triple-girder model can easily consider the warping stiffness and other section properties of the bridge deck, and at the same time keep the user-friendly features in the single-girder model. The Nanpu cable-stayed bridge, built recently in China, is then taken as a case study to verify the rationality of the proposed triple-girder model through a comparison with measured data. The study shows that the modal properties of the cable-stayed bridge obtained from the modal analysis using the triple-girder model are more reasonable and close to the measured data. Further studies of four more cable-stayed bridges in China highlight that the extent of the warping effect depends greatly on the type of bridge deck and on the type of bridge tower–cable system. A simple approach for estimating some section properties of typical open-section decks is also suggested to further facilitate the use of the triple-girder model. © 2000 Elsevier Science Ltd. All rights reserved.

汲水门大桥是一座主跨430米、双塔平行双索面、公铁两用双层斜拉桥，横跨香港马湾岛和大屿山岛之间的汲水门水道。在通车之前对该桥进行了实桥环境随机振动试验研究，以获得对桥梁抗震、抗风、健康监测、故障诊断等非常重要的结构固有模态(包括固有频率、振型及对应的阻尼比)。对主梁上的11个测站(33个测点)和两桥塔上的4个测站(16个测点)分4组进行了环境随机振动信息的记录，并利用自编的模态识别程序EDPFDM对所记录的信号进行了处理。在0～6Hz范围内共识别出主梁竖向弯曲振动为主的模态10阶，主梁横向弯曲振动为主的模态4阶，主梁扭转振动为主的模态6阶。经比较，固有频率和振型的试验结果与MSC-NAS-TRAN程序的分析结果十分接近。

s paper addresses the measurement of eight flutter derivatives of a typical oblique strip of the Tsing Ma bridge deck under skew winds. The wind tunnel test technique developed for this measurement includes the design of oblique sectional model, the development of a dynamic test rig, and the application of unifying least-square (ULS) method for identification. The eight identified flutter derivatives of discrete values are first fitted to obtain eight flutter derivative curves as functions of both wind inclination and yaw angle. Based on these curves, the effects of wind inclination and yaw angle on aeroelastic damping and stiffness, in particular on critical wind speed, are then discussed. Furthermore, the measured flutter derivatives of the bridge deck under skew winds are compared with those obtained from the empirical formulae derived from the skew wind theory. Finally, the critical wind speeds from the measured flutter derivative A2• curves are also compared with those from the A2•curves estimated by the empirical formulae. © 2002 Elsevier Science Ltd. All rights reserved.

通过气弹模型风洞试验对斜风作用下湛江海湾大桥施工阶段最长双悬臂状态的抖振性能进行了研究，结果显示：对于大跨度斜拉桥梁抖振响应法向风不一定是最不利的情况；抖振响应随风偏角呈非单调变化，最大值可能在0°～15°风偏角范围内发生；抖振响应随风速的增加近似地按两次曲线增加，并且基本固有模态对抖振响应的贡献占到了主要成份；最长双悬臂状态塔顶纵向抖振响应显著地大于裸塔塔顶纵向抖振响应，而两者随风偏角的变化形态也互不相同。试验和分析结果的比较表明，只要解决好诸如气动导纳等气动参数的取值问题，可以对大跨度桥梁抖振响应作出合理的理论预测。