[en] This paper presents a complete analysis of the aeroelastic behaviour of a deck section during the
construction stage of the Third Bosphorus Bridge in Istanbul, Turkey. The combination of the low torsional stiffness along the vertical axis and the unstable aerodynamic shape of the suspended deck section led to a torsional flutter instability for a low wind speed (9.6 m/s). This low critical wind speed was obviously very likely to occur on the site of construction, so that mitigation actions were be implemented. It was decided to cover partially the sides of the deck section in order to modify adequately its aerodynamic shape. It is demonstrated that the proposed aerodynamic counter-measures increase the critical torsional flutter wind speed up to 39.5 m/s (worst configuration), which is acceptable for the construction phase of the bridge. The proposed mitigation solution was implemented and no torsional oscillations were observed.
