Aerodynamic damping functions in vortex-induced vibrations for structures with sharp edges

Abstract

Ultimate limit state and fatigue analyses of slender structures in vortex-induced vibrations require knowledge of aerodynamic damping in the lock-in range. The aerodynamic damping depends primarily on the shape of the cross section. The paper provides an experimental database of aerodynamic damping functions for different shapes, with a focus on sharp-edged cross sections. The data are discussed with respect to existing results available for circular cross sections. The aerodynamic damping is measured directly through wind tunnel tests in forced vibrations. Wind tunnel tests in free vibrations are used to extend the functions in the range of large oscillations and to validate the model. This concept is implemented in a well-founded calculation method for vortex induced vibrations for the design of slender structures. This is suitable for code applications and is in line with the procedure described in the latest generation of Eurocode. The novelty with respect to previous models like the Vickery&Basu model consists in an aerodynamic damping parameter with positive curvature. This can be easily controlled for varying cross sections by changing the value of the function exponent.