Wake Study of Stiffening Truss and Box Girder

A 1:64 scale model of the William Preston Lane, Jr., Memorial Bridge was studied in the wind tunnel to determine possible downstream effects on a parallel structure. The model was tested in smooth flow and in a grid-induced turbulent flow with the model held rigidly and also in a mounting allowing torsional oscillation. A 3.1 to 1 box member was also tested in rigid configuration only. For the stationary truss model in turbulent flow, at a downstream distance of about 10 bridge widths, the wake is random in nature with somewhat higher turbulence intensities. For the smooth flow, significant effects are still noticeable at a spacing of over 13 widths, the maximum distance tested. The same conclusions obtained for the box, although at greater spacings. For the oscillating model in turbulent flow, a small effect remains at maximum distance, while strong effects remain for smooth flow at the same location. Testing real problems in turbulent flow is recommended.