Effect of modal damping on bridge aeroelasticity

Abstract

Abstract Estimation of modal damping is always a critical first step in the analytical estimation of the flutter and buffeting reponses of long-span suspended bridges. The impact of under or over estimation of modal damping on the aerodynamic and aeroelastic behavior of suspended bridges is not clear. This issue surfaced when a seismic retrofit of the Golden Gate birdge using viscous dampers was proposed. The affect of these viscous dampers on the flutter and buffeting response of the Golden Gate bridge needed investigation. This paper considers the affect of additional damping imposed by these viscous dampers on the aeroelastic and aerodynamic response to wind-induced excitation. This mechanical damping was introduced into the aeroelastic system as additional modal damping. A multi-mode flutter and buffeting analysis was performed for several levels of modal damping. The results of the analysis revealed that additional damping decreased the buffeting response whereas the effect in flutter stability was more complex. At different levels of damping not only did the critical flutter velocity change but also the angle of attack at which it occurred.