Vortex-induced vibration suppression and spanwise aerodynamic correlation analysis of a separated twin-box girder with baffle plates

To investigate the suppression effect of three baffle plate configurations (BP1, BP2, and BP3) within slot region on vertical vortex-induced vibration (VIV) of a separated twin-box girder, with emphasis on spanwise correlation dynamics of the vortex-excited aerodynamic lifts (VEALs). Wind tunnel tests on a spring-suspended sectional model were conducted. The results show that the installation of baffle plates, particularly BP3, significantly reduced the vertical VIV amplitudes and lock-in regions, but increased the onset wind velocity of the separated twin-box girder. It also decreases steady pressure, fluctuating pressure and lift force. The phenomenon directly correlates with the disruption of vortex shedding in the slot region and the top/bottom plates of the downstream box girder. These disruptions predominantly result from flow separation occurring at the ancillary facilities and corner structures. The spanwise correlation coefficients are amplified by the amplitudes and exhibit a monotonic attenuation with increasing spanwise distance, asymptotically approaching a non-zero constant value. The corresponding decay rate demonstrates a substantial enhancement with diminishing VIV amplitude. The spanwise correlations of VEALs vary with baffle plate configuration, which are smaller than those without baffle plates. The variation of both spanwise configuration and transverse characteristic dimensions of the baffle plates can impact the spanwise correlation of VEALs. The VIV amplitude can be significantly reduced by appropriately decreasing the spanwise correlation coefficient of VEALs. Aerodynamic optimization of baffle plate configurations to reduce the spanwise correlation coefficient of VEALs could be an effective measure to mitigate VIV amplitude in twin-box girders.