Flutter Suppression Effects of Movable Vertical Stabilizers on Suspension Bridges With Steel Box Girders

As the combination of springs and vertical stabilizers, the movable downward vertical central stabilizer (MDVCS) is proposed to further control the nonlinear flutter of super long-span suspension bridges in this paper. A series of flutter suppression tests of closed-box girders and twin-box steel girders with various MDVCSs are conducted. Based on the coupled flutter theoretical method, the sensitivity analysis of two important parameters including the height and stiffness of MDVCS are carried out to compare their nonlinear flutter control mechanism. The results show that the flutter critical wind speed (U_cr) of the closed-box girder continued to increase with the decrease of the height of the DVCS and the increase of spring stiffness, whereas the U_cr of the twin-box girder increased at first and then decreased. The cubic polynomial function and quadratic Holliday function are suitable to modify the correction coefficients of U_cr for the closed-box girder with various stiffnesses and heights of MDVCS, while the Lorentz peak-value function and cubic polynomial function are suitable to modify the U_cr of the twin-box girder. Furthermore, the MDVCS significantly changes the rules of two positive and negative aerodynamic damping ratios for the closed-box girder and two negative aerodynamic damping ratios for the twin-box girder. Besides, the peak vertical displacement amplitudes of the box girder are about half of the MDVCS, since both the height and stiffness of MDVCS alter the elliptical radius of vertical phase planes to affect the limit cycle oscillation of soft flutter, especially for the leeward MDVCS for the twin-box girder.