Abstract：On the basis of a hybrid girder cable-stayed bridge with main span of 820 meters, the wind tunnel test and CFD simulation for rigid segment model were conducted. The vortex-induced vibration performance of semi-open separated twin-box deck was studied, and a series of aerodynamic countermeasures were explored. The tests show that semi-open separated twin-box deck may suffer remarkable vortex-induced vertical vibration (VIVV) at the attack angle of +3° or +5°. It is found that flow separation generated at the railings on the sideway plays a leading role. And the maintenance rail can amplify the vibration amplitude, stemming from the fact that the small-scale vortex generated by rail may gather at the bottom of cross section to form an energy-concentrated vortex. Different types of railings on the sideway or more sharp wind fairings have no helpful effects on the VIVV. Nevertheless, extending wind fairings outward are useful but not practical. The bottom stabilizer almost doesn′t work. Both horizontal-wing lamina (HWL) and airflow-suppressing lamina (ASL) can effectively control the VIVV. HWL may put off the energy concentration of vortexes and lower the amplitude of VIVV. However, HWL can increase lock-in interval of bridge section at large attack angle. ASL is able to control the vortex-induced vibration effectively via preventing the formation of vortex on the top surface of deck.
