Three-dimensional Non-linear Analysis and Aeroelastic Model Test on Unsteady Galloping of Rectangular Column
Rectangular-like sections are prone to wind-induced self-excited vibration,commonly known as"soft galloping",due to their blunt aerodynamic shapes.Unlike classical galloping,the vibration will not diverge infinitely but converge to a limit cycle oscillation with a stable amplitude,which shows significant nonlinear characteristics of its self-excited force.Moreover,the time-varying feature of galloping vibration also reveals notable unsteady characteristics.Such unsteady and nonlinear galloping may happen on steel and rectangular-like columns,hangers,and girders used in real bridge engineering due to their blunt shapes,low-mass,and low-damping characteristics.Therefore,it is necessary to accurately predict their responses of unsteady and nonlinear galloping.To this end,by taking a rectangular cross-section with a side ratio of 3:2 as the object,the parameters of a nonlinear mathematical model for the two-dimensional galloping self-excited force were first identified.Then,considering that the nonlinearity of unsteady galloping is mainly reflected in its aerodynamic damping effect,while the nonlinear effect of its aerodynamic stiffness is relatively weak,a three-dimensional nonlinear analysis method for the unsteady galloping responses of blunt columns,considering the influence of structural mode shape and vertical mean wind profile was proposed by the modal decomposition.On this basis,case studies of theoretical analysis and aeroelastic model wind tunnel tests were carried out on the nonlinear and unsteady galloping responses of a rectangular column with a side ratio of 3:2 under two typical wind profiles.The feasibility and reliability of the proposed three-dimensional nonlinear analysis method for the unsteady galloping responses of the blunt column were verified by comparing the experimental and theoretical results.
bridge engineeringunsteady gallopingaeroelastic model testrectangular columnnonlinear analysis
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