Application scope of equivalent linear technique for across-wind response analysis of tall flexible structures considering nonlinear aero-elastic effect

Abstract

Large across-wind response of tall flexible structures becomes an increasing concern due to the significant nonlinear aero-elastic effect. The nonlinear aerodynamic damping, which is in phase of time-variant structural velocity, is usually employed to describe nonlinear aero-elastic effect. For the sake of evaluating the across-wind response of tall flexible structures within the framework of linear random vibration theory, equivalent linear aerodynamic damping model is required, which can be deduced from either harmonic balance (HB)- or statistical linearization (SL) technique. This study addressed clarifying application scope of various equivalent linear techniques for evaluating across-wind response of tall flexible structures. By conducting the Monte Carlo simulation and free-vibration wind tunnel test, it is clarified that the root-mean-squared (RMS) response calculated by the HB equivalent linear aerodynamic damping is acceptable, while is not satisfactory with respect to the SL technique especially when the structure is with lower damping level, and in the vicinity of vortex lock-in wind speed. Moreover, it is found that neither HB- nor SL technique can accurately predict the peak response. It is revealed in this study that accuracy of various equivalent linear techniques is essentially affected by probability density function of across-wind response.