Vortex-induced vibration performance and mechanism of long-span railway bridge streamlined box girder

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.