Extraction of Nonlinear Aerodynamic Damping of Crosswind-Excited Tall Buildings from Aeroelastic Model Tests

Abstract

This paper presents a new approach for extracting nonlinear aerodynamic damping of crosswind-excited tall buildings from response statistics at different levels of structural damping obtained from aeroelastic model tests. The aerodynamic damping at a given wind speed was modeled as a polynomial function of the amplitude of the harmonic building motion, which leads to analytical solutions of the standard deviation (SD) and kurtosis of the crosswind response under stochastic load excitation. As an inverse problem of response analysis, the nonlinear aerodynamic damping model coefficients can be identified from known response SD and kurtosis through a nonlinear optimization algorithm. The crosswind loading spectrum at the structural frequency can be determined from rigid model testing or treated as an unknown. The accuracy of this identification scheme is first illustrated using crosswind response of a tall building calculated from a given nonlinear damping model. It is then applied to a square-shaped tall building using aeroelastic model testing data under boundary-layer flows. The limitation of the conventional approach, which did not account for the response kurtosis, is highlighted. With the proposed approach, the effect of approaching flow characteristics on crosswind aerodynamic damping is examined.