Structural and aerodynamic stability analysis of long-span cable-stayed bridges.

摘要

The increasing span length of the modern cable-supported bridges makes the aerodynamic stability a major concern for this type of structure. Flutter, which is a self-excited aerodynamic instability phenomenon, has become one of the governing criterion in the design of the long-span bridges.; The determination of the dynamic characteristics of the bridge is an essential first step in the flutter analysis. The common practice is to use the 3D equivalent beam finite elements to develop the analytical model. Some assumptions on the behaviour of the bridge response must be made in order to simulate the mass and stiffness properties of a complex bridge girder by the equivalent beam, which may be over-simplified and thus have a significant impact on the accuracy of the results. Further, the state-of-the-art 3D flutter analysis models for bridges based on the equivalent beam finite elements cannot account the spatial distribution effects over the bridge deck cross-section. A major component of the present research is to study the application of the finite strip method in the dynamic characteristics and flutter analysis of the long-span cable-stayed bridges. The mass and stiffness properties of the bridge girder can be accurately represented by minimum modelling effort. The spatial distribution effects of the aerodynamic forces can be taken into account by distributing the load on the individual finite strip elements.; Under the dynamic loads, the vibrational behaviour of the cable-stayed bridges involves the motion of the bridge girder, pylon(s) as well as the stay cables. The transverse vibration of the cables, which can be significant in some cases, are usually neglected in most of the research. The impact of the cable vibration effect on the dynamic characteristics and the flutter behaviour of the long-span cable-stayed bridges having different combinations of structural layout and aerodynamic properties is studied in the current research.; The unique properties of the CFRP make it an ideal substituent cable material of the traditional steel to be used in the long-span cable-supported structure. Very few research has been conducted to study the bridge response by using CFRP cables. In the present study, the impact of using CFRP cable on the dynamic characteristics and the flutter response of the cable-stayed bridges having different combinations of structural layout and aerodynamic properties are carried out.