Effects of Vertical Motion on Nonlinear Flutter of a Bridge Girder

Abstract

This study addresses the effects of vertical motion on the nonlinear flutter response of a double-deck truss girder based on section model wind tunnel tests. Six dynamic systems with the same bridge deck section were tested under various wind angles of attack. The nonlinear flutter characteristics under different cases were fully captured. The potential effect of vertical motion on coupled nonlinear flutter was investigated by conducting an additional single-degree-of-freedom wind tunnel test. The aeroelastic mechanism concerning the vertical motion that affects the nonlinear flutter performance is revealed by qualitatively estimating the contribution of coupled aerodynamic damping to the total damping. Results showed that vertical motion introduces noticeable negative damping to the system thus increases vibration amplitude and reduced onset wind speed at lower wind angles of attack, while the vertical motion will be less important at large wind angles of attack since its contribution to the total damping is relatively small. Finally, a preliminary method is proposed to identify nonlinear aerodynamic damping, which helps to understand the participation of vertical motion on coupled nonlinear flutter and to interpret the amplitude dependence of nonlinear flutter.