Identification of nonlinear aerodynamic damping of cross-wind excited slender structures in atmospheric boundary layer flow

Abstract

Due to the low natural frequency and low damping of slender structures, the crosswind aero-elastic effect become dominant around the vortex-resonance wind speed and can lead to undesired crosswind responses. For understanding and describing the aero-elastic effect of slender structures, aerodynamic damping is usually adopted. This study suggested an identification procedure for crosswind aerodynamic damping of slender structures by curve-fitting the probability density function (PDF) of the crosswind response. Firstly, the aerodynamic damping is described by a generalized Van der Pol (GVDP) model, and the analytical solution of response PDF, which is a function of the parameters of GVDP model, is derived by the equivalent nonlinear equation method. Next, the proposed identification method was validated by stochastic simulation of a crosswind-excited tall building. Finally, free-vibration wind tunnel test of a slender structure with slenderness ratio equal to 12 and 20 at open flat terrain was conducted and aerodynamic damping was then quantified by the present method. It is found that the present method provides a robust and accurate identification of crosswind aerodynamic damping of slender structures in atmospheric boundary flow.