Nonlinear vortex-induced force model identification by combination of growth- and decay-to-resonance vibrations and applications

This study addresses a key limitation in motion-described vortex-induced force (VIF) modeling connect to vortex-induced vibration (VIV) of bridge decks: parameter identification has traditionally based on incomplete response histories. Wind tunnel tests in this study are conducted on a sectional model with synchronized measurements of displacement, aeroelastic force, motion frequency, and phase angles. After quantifying the non-wind-induced aerodynamic damping and stiffness in still air, a nonlinear VIF model was identified by jointly using the growth-to-resonance (GR) and decay-to-resonance (DR) processes. The identified parameters are expressed in a motion-amplitude-dependent form according to the extracted energy-trapping characteristics. The combined GR–DR procedure improves the completeness of model parameters, extends their applicability to both higher and lower mechanical damping conditions, and avoids the parameter-range insufficiency reported in earlier three-dimensional applications. These results establish a more robust basis for nonlinear VIF identification and three-dimensional VIV analysis.