An improved method for calculating the vortex-induced vibration (VIV) of bridges is proposed in this article. In this method, the nonlinear characteristics of the additional aeroelastic effects during VIV versus structural amplitude are first identified through an instantaneous identification method and polynomial fitting. The expression for the aeroelastic effects as a function of structural amplitude is then transformed to the function of structural velocity and/or displacement to calculate the limit-cycle oscillation of the deck. The proposed method was validated through an experiment with different mass-damping conditions. The results indicate that the generalized polynomial model with parameters identified on one particular mass-damping condition can be used to calculate the VIV response of the deck within a certain range of mass-damping values. Based on this method, the VIV performance of a real bridge was calculated by considering the influences of modal shape and spatial coherence of VIV forces. Compared with the traditional method, the applicability of which is limited to a particular mass-damping condition for which the model parameters were estimated, the proposed method will significantly reduce the uncertainty in the prediction of the VIV performance of a real bridge.

This paper presents an experimental investigation on wind-induced vibrations of a suspension bridge with ultimate main span length, including flutter and buffeting. Since the upper limit of a suspension bridge's main span can reach more than 5,000 m based on strength and weight of steel main cables, a feasible prototype with a span arrangement of 2,000 + 5,000 + 2,000 m has been proposed. In order to improve flutter stability, a twin box girder has been designed with a 40 m slot in center and two 20 m wide decks suspended by four main cables. Its full aeroelastic model was designed and manufactured with the geometrical scale of 1:620, and the wind tunnel testing was carried out under smooth flows and turbulent flows for different angles of attack. A big difference in critical flutter speed was found between the proposed slotted girder and corresponding slot-sealed girder, which verifies the necessity of a widely-slotted (WS) twin box girder for a super-long suspension bridge. Among three angles of attack, the critical flutter speed under smooth flow has the maximum value of 80.9 m/s at −3° and the minimum value of 51.4 m/s at 3°. On-coming turbulence will not only cause buffeting responses but also influence the critical flutter speed in an unfavorable way.