Nonlinear self-excited forces and aerodynamic damping associated with vortex-induced vibration and flutter of long span bridges

Abstract

This study presents a comprehensive investigation of nonlinear self-excited forces and negative aerodynamic damping associated with vertical and torsional vortex-induced vibrations (VIVs) and coupled flutter of bridges. Wind tunnel test of a spring-supported streamlined box deck section model is carried out to characterize vertical and torsional VIVs and flutter at different angles of attack. A Hilbert Transform-based approach is proposed to determine the amplitude-dependent aerodynamic damping and other response characters. The self-excited forces in terms of flutter derivatives are subsequently extracted as a polynomial functions of vibration amplitude. The flutter derivatives are validated by comparing predicted VIV and flutter amplitudes with wind tunnel data. The VIV and flutter amplitudes of a three dimensional (3D) suspension bridge are further predicted with consideration of spanwise variation of self-excited forces. The influence of partial spanwise correlation of self-excited forces on VIV is also examined. The 3D analysis leads to a significant lower VIV and flutter amplitudes as compared to 2D analysis. The study not only presents an effective analysis approach and also provides new insights that lead to improve understanding and quantification of nonlinear self-excited forces and their effects on bridge VIV and flutter.