Effects of structural damping and deck details on the vortex-induced vibration mechanism of a streamlined single-box girder

Vortex-induced vibration (VIV) of streamlined box girders is highly sensitive to structural damping and deck details, yet the mechanisms by which local deck details destabilize an otherwise streamlined section remain insufficiently understood. This study investigates the VIV mechanism of a streamlined single-box girder through sectional-model wind tunnel tests, including measurements of shedding characteristics, aeroelastic responses, and smoke-wire flow fields under the operational configuration, a maintenance configuration with temporary water-filled barriers, and several modified deck-detail configurations. In the operational configuration, the measured Strouhal number ranged from 0.104 to 0.127, and distinct vertical and torsional lock-in regions were observed under low damping conditions. Increasing structural damping markedly reduced the response amplitude and could effectively suppress lock-in, indicating typical low-damping limit-cycle oscillation behavior. The temporary barriers reduced the Strouhal number to 0.089–0.121, widened the lock-in range, and significantly amplified the vibration response. Comparative configuration tests further showed that upper-deck details exerted a stronger influence on aerodynamic instability than the examined bottom details. Flow visualization revealed that deck details promoted stronger separation and wake unsteadiness, whereas the temporary barriers induced pronounced step-like leading-edge separation and inhibited shear-layer reattachment. The results highlight the combined roles of low structural damping and deck-detail-induced flow modification in governing VIV behavior.