An integrated approach of vortex-induced vibration for long-span bridge with inhomogeneous cross-sections

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Conventional models resolve the vortex-induced vibration (VIV) problem for long-span bridge with an essential assumption that the cross-section is uniform. When the cross-sections are altered in span-wise direction, i.e., inhomogeneous cross-section design, conventional approaches are inapplicable, and the global VIV becomes ambiguous and difficult to evaluate directly. This paper presents an integrated approach which combines the Scanlan's nonlinear VIV model and an aerodynamic damping model to characterize the global VIV for long-span bridge with inhomogeneous cross-section design. In the proposed approach, the Scanlan's nonlinear model is utilized to characterize the vortex-induced motivating force on cross-sections at lock-in whereas the aerodynamic damping model is employed to describe the air-induced hindering effect on cross-sections away from lock-in. The parameters in the integrated model are identified using either a ‘decay-to-resonance’ method or free decay vibration test via sectional model tests. The proposed approach is validated through a proof-of-concept wind tunnel experiment. An engineering practice of an urban rail-road long-span bridge with span-wise inhomogeneous cross-section design is demonstrated and discussed as an example. The VIV performance with and without considering inhomogeneous effects are evaluated and compared. The effects of various section deployment plans as well as their global performance are investigated and discussed.