An alternative aerodynamic measure for improving Π-shaped girders vortex-induced vibration performance: Flexible L-shaped deflectors

This study proposes a flexible aerodynamic strategy to mitigate vortex-induced vibrations (VIVs) in Π-shaped bridge decks. The concept is based on the deformation and flapping motion of flexible plates installed along the deck edges. To evaluate the effectiveness of this approach, wind tunnel tests were conducted on a Π-shaped section with an aspect ratio of 8.35. Three types of mitigation devices, i.e., flexible L-shaped deflectors, lower central stabilizing plate, and lower edge stabilizing plates, were installed with various lengths and stiffnesses to examine their aerodynamic performance. Numerical simulations were further carried out to clarify the flow–structure interaction mechanism associated with the flexible L-shaped deflectors. The experimental results show that the flexible L-shaped deflectors demonstrate superior mitigation performance for both vertical and torsional VIV of the Π-shaped section, with improved suppression effectiveness as their height or stiffness increases. The flow mechanisms indicate that VIV suppression is primarily achieved through a combination of upstream flow deflection caused by the plate deformation and downstream vortex modulation induced by the flapping motion. This mechanism modulates the vortices at the trailing edge of the girder, reducing their characteristic size and energy and altering the spatial orientation of vortex shedding in the wake.