Experimental study on vortex-induced vibration and aerodynamic characteristics of a closed box girder with L-shaped deflectors

This study investigates the vortex-induced vibration (VIV) performance of closed-box girders with and without L-shaped deflectors through synchronized vibration and pressure measurements in wind tunnel tests. Spectral proper orthogonal decomposition (SPOD) was employed to analyze the fluctuating wind pressure field during the VIV process. The results showed that the addition of L-shaped deflectors intensified vertical bending VIV while slightly suppressing torsional VIV by significantly altering the aerodynamic characteristics of the girder surface. Specifically, the deflectors increased the contributions of aerodynamic forces from the lower surface and windward-side top plate to VIV forces, leading to greater vertical bending vibration amplitudes. Conversely, they reduced the contributions from the windward top plate and inclined web, resulting in decreased torsional vibration amplitudes. SPOD analysis revealed that the first-order mode dominated the VIV process. The deflectors enhanced the peak intensity of acoustic wave modes on the upper surface during the peak of vertical bending VIV while reducing the wavenumber and weakening the modal evolution intensity during the peak of torsional VIV.