GENERALIZED FORCE CALCULATION METHOD AND UNCERTAINTY ANALYSIS OF NONLINEAR MODE STRUCTURE IN HFFB TESTS

Based on the high-frequency-force-balance test, an improved method for evaluating wind-induced response of nonlinear mode-shape structures is proposed. The vertical distribution of wind load is assumed to be the same with gust wind pressure, then real mode shapes are used to calculate the generalized wind forces. The computational formulas of generalized wind forces and wind-induced responses are derived, and the higher modes can be considered, so that the high-frequency-force-balance method can accurately evaluate the wind-induced responses and equivalent static wind loads of nonlinear mode shape structures. A high-frequency-force-balance test of a tall structure with changes in mass and stiffness is conducted. Comparing the proposed method with linear mode shape method, the computational error of the linear mode assumption is analyzed, and it shows that the acceleration response of a nonlinear mode shape structure can be 40% overestimated applying the linear mode shape method. The influence of the load distribution uncertainty is studied. The results show that under the assumption of gust wind profile load, the load distribution uncertainty has little effect on the maximum acceleration response, which proves the applicability of the proposed method.