Non-linear aerodynamic load and parameters estimation for a SDOF wind- structure coupling system in wind tunnel test

摘要

Knowledge of the system parameters and wind load acting on a structure is essential for the analysis of vortex induced vibration of a structure. Method to acquire such information is scarce due to the complexity of nonlinear vibration of the structure. A strategy to identify the non-Linear system parameters and unknown excitation of a single-degree-of-freedom system under wind induced vibration is proposed. The variations of system parameters and unknown excitations including the self-excitation forces of the system under different mean wind speed are analyzed. The system stiffness varies by approximately +/- 10% from the original value, while the system damping can be reduced as much as 60% in a vortex induced vibration (VIV) event. The pure aerodynamic force (excluding the self-excitation force) in the VIV event is identified with the help of the measured aerodynamic force acting on a rigid model of the system under the same experimental conditions. The intensities of the second and third orders self-excitation forces can be up to 30% and 80%, respectively compared to the pure aerodynamic force. This proposed strategy has been checked capable to obtain information on the aerodynamic characteristics of the target bridge structure with notable VIV phenomenon and large turbulent intensity which are essential for preliminary bridge design.