Side-Surface Openings Effect on Aerodynamic Performance of Box Girders in Tandem

A butterfly web girder is a box girder that has discretely distributed side-surface openings. Due to these openings, butterfly web girders show better aerodynamic performance than conventional box girders. This study aims to investigate the effects of side-surface openings on the aerodynamic instability of a box girder when it is placed in tandem with another girder. In addition, this study aims to investigate whether the aerodynamic instability of one girder is affected by the side-surface openings of an adjacent girder. A series of wind tunnel tests will be carried out on a butterfly web girder and conventional box girder, with another rigidly supported butterfly web girder or conventional box girder, respectively, at its upstream or downstream side. The fixed downstream girder increased the galloping instability of the upstream girder, and the fixed upstream girder amplified the vortex-induced vibration of the downstream girder. The side-surface openings of the upstream girder stabilized its galloping and vortex-induced vibration, irrespective of the type of girder downstream. The side-surface openings of the downstream girder stabilized its vortex-induced vibration independent of the type of girder upstream.