Flutter control optimization for a 5000 m suspension bridge with active aerodynamic flaps: a CFD-enabled strategy

The theoretical model of self-excited aerodynamic force with four active flaps attached to the deck is proposed in this study for a 5000 m bridge with a broad slotted section. The feedback control method is introduced with details, and the phase lag and gain coefficient of the flaps according to the vertical and torsional motions of the deck are used as key control parameters. And the assumption of linear superposition of the aerodynamic forces of the deck and flaps is verified by computational fluid dynamics (CFD) simulations. On this basis, considering the angle of attack (AoA) effect, the flutter derivative of the deck-flap system is identified utilizing forced vibration technology in different states, and the flutter analysis is carried out by the two-dimensional two-degree-offreedom method. The results indicate that the feedback control based on the vertical and torsional motions can effectively increase the critical wind speed of flutter of the system, and the effective control range of each flap is revealed. Besides, it is found that there is almost no stable phase lag which can make the critical state of the system be improved at all AoAs, the AoA has a great influence on the control parameters. Finally, the control effects using the double flaps are compared, and using the flaps on the outside of the deck gives a better flutter improvement than that using the flaps on the inside of the deck. Flutter performance of deck-flaps system can be improved even more by using more flaps. When the four flaps are activated, the flutter performance of the system can be improved by 45.13% under the unity gain coefficient.