THE EFFECTS OF UPSTREAM GUSTING ON THE AEROELASTIC BEHAVIOR OF LONG SUSPENDED-SPAN BRIDGES (TURBULENCE, STABILITY, VORTEX, WIND, TUNNEL)

The effect that the presence of upstream gusting has upon the ability of long suspended-span bridges to sustain wind loads has been the subject of a certain amount of controversy among bridge designers and wind engineers. Wind tunnel studies of full bridge models, using passively-generated small-scale turbulence, have indicated that upstream turbulence exerts a stabilizing influence on the aeroelastic response of bridges. These wind tunnel studies have been criticized because the simulated gusts are usually smaller than the deck width of the model, whereas field measurements of the prototype conditions indicate that upstream gusts should be substantially larger than typical bridge deck widths. Theoretical analyses, based on stochastic parametric excitation models, have indicated that the presence of large-scale upstream gusting should have a destabilizing effect upon bridge deck sections.;This dissertation presents the results of wind tunnel experiments in which bridge deck section models were subjected to gusting flow regimes with simulated turbulence that contained gusts several times larger than the section model width. The large-scale gusting flow was produced by the novel technique of flapping-airfoil gust generation. Three section models were tested under smooth and gusting flow conditions. These experiments measured the change in the flutter derivatives, buffeting response and vortex shedding proclivities that are caused by upstream gusting. The preliminary results of this study indicates that large-scale upstream turbulence can decrease the flutter stability, increase the buffeting response and suppress the vortex-shedding action of bridge deck section models.