Wind-induced pressures around a sectional twin-deck bridge model: Effects of gap-width on the aerodynamic forces and vortex shedding mechanisms

The effects of gap-width on the aerodynamic characteristics of a twin-deck bridge in a nominally smooth flow were investigated in this paper, with a specific goal of studying the vortex shedding mechanisms of the bridge deck. Simultaneous pressure measurements were carried out on five deck configurations, using a rigid sectional model of a twin-deck cable-stayed bridge with different gap-widths. Stream-wise mean and fluctuating pressure distributions around the bridge deck were studied to investigate the potential excitation mechanisms caused by the gap-widths at various angles of wind incidence. The effects of gap-width on the static force and moment coefficients were also analyzed. The results demonstrated that the gap-width has the potential to significantly affect the pressure distribution and hence the corresponding aerodynamic performance of the bridge deck. In addition, the analyzed results showed that the twin-deck bridge in this study is susceptible to vortex shedding and its Strouhal number gradually increases with increasing gap-width due to the change of flow regime around the bridge deck. This knowledge is essential for the complete aerodynamic evaluation of a twin-deck bridge.