In previous studies, a twin-deck configuration with a centre gap has been proven to be an effective means of improving the flutter responses by altering the surface pressure distribution around the bridge deck. Hence, twin-deck or even multi-deck configurations have a great potential to be widely employed in future super long-span bridges....[ Read more ]

In previous studies, a twin-deck configuration with a centre gap has been proven to be an effective means of improving the flutter responses by altering the surface pressure distribution around the bridge deck. Hence, twin-deck or even multi-deck configurations have a great potential to be widely employed in future super long-span bridges.

The primary objective of this study is to investigate the effects of gap-width and angle of wind incidence on the Stonecutters Bridge which features a twin-deck design. A 1:80 geometry scale static sectional model was fabricated to allow for simultaneous pressure measurements at 448 locations to calculate the time history of aerodynamic forces and pitching moment by spatial integration of the surface pressures. Five gap-widths corresponding to 0 m, 1 m, 7.5 m, 14.3 m and 21.1 m at prototype scale were used to provide gap-width to total deck width ratios of 0 %, 2.5%, 16.1 %, 26.8 % and 35.1 %.

The flow excitation mechanisms were found to change with the gap-width and angle of wind incidence as illustrated by the stream-wise mean and fluctuating pressure distributions around the test configurations. As the gap-width is increased, mean positive pressures were recorded at the upstream windward surface of the downstream deck which results in significant increase of drag force. The magnitude of the lift and pitching moment coefficients was found to increase with the angle of wind incidence and there is no obvious trend with respect to the length of the gap-width. In addition, the aerodynamic admittance functions for each of the tested configurations were also identified to quantify the effectiveness of the velocity fluctuations at generating aerodynamic force on a bridge deck. The pitching moment admittances were shown to increase gradually with increasing gap-width over the whole range of reduced frequency considered.

Further research can include various bridge deck shapes which have the potential to be used for future super long-span designs. Larger ranges of turbulence intensities and length scales should be tested systematically to obtain a clearer picture of the corresponding wind effects on the bridge decks.