VORTEX-INDUCED VIBRATIONS OF LONG-SPAN CONTINUOUS BRIDGES WITH STEEL TRUSS-STIFFENED BOX-GIRDER

Vortex-induced vibrations (VIVs) are one of the most critical issues for continuous beam bridges with long spans. The proposed 4th Bridge at Macao is a continuous-beam bridge made of steel truss-stiffened box girders with variable height and asymmetric configuration, and the bridge girder has a width of approximately 50 m and complex aerodynamic shape owing to various accessory components. The VIV performance of the 4th Bridge at Macao is studied by wind tunnel tests on 1∶70 sectional models, and the effects of wind attack angles, turbulence intensity, structural damping, wind barrier are compared. Two typical cross sections at the L/2 and L/3 of the main span are tested. The results shown that the cross-section of truss-stiffened box-girder may generate VIVs under negative wind attack angle, and the VIV of two cross-sections at negative attack angles are different, implying the effect of truss on VIV is significant. The results also shown that the asymmetry of the cross-section may significantly affect the VIV performance of the continuous beam bridge with steel truss and variable cross-sections. The amplitude of the VIV response can be reduced effectively by lowering the permeability of the outer barrier and adopting a spoiler with a reasonable placement. Finally, the parameters of the wake oscillation model for the simulation of vortex-induced vibrations are identified based on the experimental results, which can accurately reflect the relation between the amplitude of VIV and the wind speed.