Postflutter Analysis of Bridge Decks Using Aerodynamic-Describing Functions

An aerodynamic describing function (ADF)-based model for simulating the nonlinear self-excited forces on bridge decks is developed, where the ADFs can be conveniently identified using the experimentally or numerically obtained free or forced vibration data. An efficient calculation procedure based on the ADFs is accordingly established to predict the nonlinear flutter state and/or postflutter limit cycle oscillations (LCOs). Two numerical examples are utilized to demonstrate the simulation accuracy and efficiency of nonlinear bridge flutter with the proposed ADF-based model. The capabilities of the ADF-based model in capturing typical features of nonlinear postflutter vibration such as LCO and a hysteresis phenomenon are demonstrated. A nondimensional postflutter index is designed to quantitatively assess the postflutter performance of bridge decks. Finally, the effects of structural dynamics and aerodynamic properties (e.g., structural damping ratios, natural frequencies, and aerodynamic derivatives) on the postflutter behavior of a bridge deck are examined in terms of the wind speed extension after the critical state with acceptable postcritical vibrations and the proposed postflutter index.