Study On Measures Against Vibration And Vortex-induced Vibration Characteristics Of Edge Girder Composite Beam Cable-stayed Bridge

In recent years, the number of edge girder composite beam cable-stayed bridgesis growing rapidly, for its convenient construction, short construction period andlighter weight. However, this type of bridges is proved to be susceptible towind-induced vibrations. Vortex-induced vibration(VIV) is a self-excited self-limitingvibration, which may occur at relatively low wind speed. The response amplitude isusually moderate but can cause serviceability or fatigue problem; therefore, it is ofsignificant importance to investigate the characteristics of VIV of these bridges andmethods of improving their performances. In order to achieve this goal, section modelwind tunnel test and CFD numerical simulation were both used in this paper. Themain contents of this thesis are as follows:1. Mechanism of vortex-induced vibration of bridges was described. The detailsof research methods, the influence factors and VIV countermeasures were presentedand discussed. The main problems of VIV of composite beam cable-stayed bridgescame forward as a basis.2. Details of the wind tunnel tests and the experimental results for three typicaledge girder composite beam cable-stayed bridges were provided. The experimentswere designed to investigate the characteristics of vortex-induced vibration of edgegirder composite beam with VIV countermeasures. Based on the experimental resultsand other successful examples in suppressing VIV of the similar bridges, promisingstabilizer to improve the wind-resistance stability of edge girder composite beamcable-stayed bridges was proposed.3. The influences of scale ratio on characteristics of VIV and the controlefficiency of aerodynamic measures were analyzed, using two different scaled sectionmodels of typical bridge. The scale ratios for the large scaled section model and thesmall scaled section model are1/25and1/50, respectively.4. Numerical simulations of flow behaviors behind stationary section model andVIV of oscillating section model were discussed. The results, including the staticaerodynamic coefficients, the Strouhal number, and the vortex shedding frequency,the lock-in region and response amplitude were obtained for the initial design, as wellas the improved design with recommended aerodynamic countermeasures.