Wind-induced vibration performance of suspended double-deck closed box girder bridge deck

A suspended double-deck closed box girder bridge deck was taken as the research object, and the influences of structural static coupling and aerodynamic interference on the wind-induced vibration performance of the bridge deck were studied through a wind tunnel test. The variational mode decomposition method was used to perform the mode decomposition on experimental monitoring signals and identify flutter modes. A vibration morphology vector diagram and a phase diagram were used to analyze the coupling degree of flutter bending and torsion and the phase difference of the bending and torsion. Flutter derivatives were identified by the least square method, and the aerodynamic damping of the flutter was identified by the flutter derivatives based on the incentive-feedback principle. Research results show that under the joint action of structural static coupling and aerodynamic interference, soft flutter occurs on the lower section, and the vertical and torsional vibration participation coefficients are 0.85 and 0.53, respectively. The flutter morphology tends to be a vertical vibration morphology. The lower section flutters under the action of self-excited aerodynamic force, and the decrease in the phase difference of the self-excited aerodynamic force makes the phase difference of the flutter bending and torsion reduce to 81.29°. However, the upper section performs a forced vibration under the action of a structural coupling force, and the phase difference of the bending and torsion of the upper section is determined to be 100.81° under the influence of the phase difference of the structural coupling force. The aerodynamic damping of the vertical vibration in the lower section mainly comes from the negative damping of a self-excited lift force of vertical velocity and the negative damping of a coupled lift force generated by the bending and torsional velocity through the incentive and feedback, which account for 60% and 40%, respectively. The aerodynamic damping of the torsional vibration in the lower section mainly comes from the positive damping of a self-excited lift force torque of torsional velocity and the positive damping of a coupled lift force torque generated by the bending and torsional velocity through the incentive and feedback, which account for 45% and 50%, respectively. Therefore, for the suspended double-deck closed box girder bridge deck, the soft flutter of the lower section is inclined to the vertical vibration morphology under the aerodynamic negative damping drive of the vertical vibration, and the soft flutter of the lower section induces a soft flutter with a bending-torsional coupling of the vibration system for the suspended double-deck bridge deck. 1 tab, 17 figs, 35 refs.