Abstract
The turbulent wind field around a suspension bridge deck is studied using eleven months of full-scale records from sonic anemometers mounted above the girder. Using the mean and turbulent velocity characteristics, we demonstrate that the bridge structure can significantly distort the flow. More precisely, the friction velocity, the variance of the fluctuating vertical velocity and the mean wind incidence angle are underestimated on the downstream side of the deck. The local topography is also found to influence the flow in a non-negligible way, such that turbulence characteristics differ significantly from those observed in flat and homogeneous terrains. For a hexagonal girder with a width to height ratio B∕H ≈ 4.5, deck-induced flow distortion is still observed on the downwind side of the girder at a height above the road equal to 3.6H. This further supports the idea that wind measurements from a suspension bridge should rely on anemometers on both sides of the deck to mitigate flow distortion. The improved flow description combined with high-resolution acceleration records of the deck provides a simulation of the wind-induced response of the bridge with a level of accuracy that is rarely achieved in full-scale. In particular, the limits of a wind model based on flat terrain assumption as well as the limits of the strip theory are highlighted by the recorded data and the improved modelling of the bridge buffeting response.
Highlights
Measurements of wind turbulence above the deck of long-span cable-suspended bridges in full-scale can be traced back to the 1970s [1,2]
Eleven months of wind velocity data collected by sonic anemometers mounted above the deck of a suspension bridge crossing the inlet of a fjord in south-western Norway have been studied
Using an improved and extended bridge instrumentation as well as a rigorous data post-processing focusing on high-quality data only, the different sources of flow distortion have been identified, leading to the following findings:
Summary
Measurements of wind turbulence above the deck of long-span cable-suspended bridges in full-scale can be traced back to the 1970s [1,2]. Jensen and Hjort-Hansen [1] noted for the case of the Sotra suspension bridge (Norway), which has a truss girder, that the anemometer records collected 3 m above the upwind side of the deck were influenced by the bridge structure. This influence was, assumed small enough to be neglected. Hay [3,9] estimated the power spectral density (PSD) of the along-wind and vertical velocity components at two positions above
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