Numerical study on suppression of vortex-induced vibrations of box girder bridge section by aerodynamic countermeasures

This paper investigates the mechanism of reduction in the amplitude of vortex-induced vibrations for a box girder bridge section in the presence of aerodynamic countermeasures using 3D LES turbulence model. Being the basic configuration for the bridge section, the aeroelastic instability of rectangular section with an aspect ratio of 4 is investigated in heaving mode under smooth flow conditions and the wake characteristics are examined. Thereafter flow around box girder section having width to depth ratio of 3.81 in the presence of aerodynamic countermeasures is analyzed and the effect of these countermeasures on the unsteady lift forces is evaluated using forced oscillation simulations. Then response of the box girder section in the presence of such aerodynamic countermeasures is investigated by conducting the free oscillation simulations, and the predicted amplitudes of vibration are compared with the experimental results. Flow visualization is employed to clarify and understand the modified flow characteristics around bridge section in the presence of aerodynamic countermeasures resulting in a reduced amplitude of vibration. Further a method based on forced oscillations to identify the reduced velocity corresponding to the maximum amplitude of vibration is proposed.