Pressure distribution, aerodynamic forces and dynamic response of box bridge sections

Static and dynamic wind tunnel tests were carried out in smooth flow on a section model of the Sunshine Skyway Bridge. Deck surface pressures, support forces, structural response, as well as wake flow velocities were measured in the tests. In this paper, a first step is made to investigate the characteristics of the aeroelastic behaviour of a bridge deck, by relating the mean and fluctuating aerodynamic forces, deck pressure distributions and dynamic response at different wind speeds, and by comparing their values with those measured on the stationary deck. Three different response regimes of forced motion, torsional vortex shedding lock-in and torsional flutter were observed, associated with different ranges of the oncoming wind speed. In the forced vibration regime the aerodynamic forces and the pressure distributions compare very well to those measured in the static tests, indicating a quasi-steady behaviour. In the lock-in and flutter regimes, however, these quantities take values quite different from those measured on the stationary model, showing the nature of the aeroelastic interaction.