Impact of geometrical details on flutter stability of twin-box bridge decks

Twin-box bridge girders are favored for long-span bridge designs due to their superior aerodynamic performance. Recent studies conducted by the authors reveal an important phenomenon termed the nose-up effect, where the critical flutter wind speed increases with the girder's nose-up rotation. This contrasts with streamlined mono-box decks, which achieve the highest flutter wind speed at zero angle of attack. Wind tunnel tests on the 1915 Çanakkale Bridge deck evaluate the effects of gantry rails, wind screens, gap sizes, and walkway porosity on flutter stability and the nose-up effect. Findings shows that these geometric factors significantly impact flutter stability, both individually and in combination. This research aids in optimizing the twin-box girder designs for enhanced long-span bridge performance. Furthermore, this paper precents a simplified flutter analysis, linking the slope of the static moment coefficient to the flutter wind speed relative to the angle of attack.