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To investigate the vortex-induced vibration (VIV) characteristics of a narrow-streamlined railway box girder and optimize its VIV performance, a long-span railway cable-stayed bridge was analyzed. Based on sectional model wind tunnel tests, the influence of the wind attack angle and the damping ratio on the VIV performance of the girder was investigated. The main inducing factors of the VIV of the narrow railway box girder were explored and a series of corresponding optimization schemes was put forward. The results show that there is no VIV when the wind attack angles are −5°, −3° and 0°, and the damping ratio is 0.2%. The non-dimensional maximum amplitudes 1000 y / D of the girder at wind attack angles of +3° and +5° are 14.4 and 19.4, respectively. The maximum amplitudes decrease with the increase of the damping ratios. The railing base is the influence factor that induces the vertical VIV, because the separation vortices between the railing base and ballast wall, as well as behind the railings, cause the VIV of the railway steel box girder. Compared with that of the girder section with the ballastless track board, the non-dimensional maximum vertical VIV amplitude of the girder without the ballastless track board greatly increases from 19.4 to 63.5, which could effectively suppress the VIV of the main girder. Lastly, in the construction state, vertical VIV occurs for girder sections I and II, which have respective aspect ratios of 4.3 and 4.6, at wind attack angles of +3° and +5°. Girder section III, which has a 6.7 aspect ratio and is more streamlined, does not have a VIV. The greater the aspect ratio of the bridge girder, the better the VIV performance. The relevant results could serve as a guide for wind resistance design of railway streamlined box girders. [ABSTRACT FROM AUTHOR]

This study investigates the influence of turbulence on the aerostatic coefficients of typical bridges by obtaining force measurements via the simulation of turbulence in wind tunnels. The traditional simulation method for turbulence based on spires and grilles cannot be employed for the accurate simulation of the large integral scale of turbulence in an actual wind field. Thus, in this study, the turbulence integral length scale was effectively increased using an active control grid. The wind fields of different turbulence integral scales were generated by controlling the vibration frequency of the active control grid. The aerostatic coefficients of five typical bridge sections (single-box girder, twin-box girder, truss girder, edge girder, and edge-box girder) were measured under turbulent and uniform flow. The test results were compared and analyzed, which revealed that the drag coefficients increased in accordance with a decrease in the reduced turbulence integral length scale, and they were lower under turbulent flow than under uniform flow. [ABSTRACT FROM AUTHOR]

During the cantilever construction stage, long-span sea-crossing twin-box cable-stayed bridges exhibit low stiffness, low natural frequency, and low damping ratio compared to the completed bridge state, making them susceptible to large buffeting responses under the high design wind speeds typical of coastal areas. Accurate calculation of the buffeting response during the bridge construction period is essential for enhancing construction safety. In this study, China’s Huangmaohai Bridge is used as a case study to introduce the three-dimensional aerodynamic admittance function (3D-AAF) of a twin-box into the buffeting analysis theory for long-span sea-crossing twin-box cable-stayed bridges. The 3D-AAF and the spanwise coherence function, key parameters of the buffeting force, were obtained through large-scale section model tests. These parameters describe the unsteady and spanwise distribution characteristics of the buffeting force. The self-excited force was calculated using the Scanlan model. Subsequently, the buffeting response of the bridge was calculated and compared with the results from the full bridge aeroelastic model test. The results demonstrate that the theoretical calculations are in reasonable agreement with experimental values, proving that the frequency domain buffeting analysis method based on 3D-AAF for long-span twin-box cable-stayed bridges is reliably accurate. [ABSTRACT FROM AUTHOR]