Direct Approach to Extracting 18 Flutter Derivatives of Bridge Decks and Vulnerability Analysis on Identification Accuracy

Abstract

The extraction of 18 flutter derivatives of bridge decks from three degree-of-freedom (3-DOF) free vibration data using a novel direct approach is addressed in this study. Different with many conventional methods that construct a system state matrix, this approach directly extracts 18 flutter derivatives using the aeroelastically modified modal parameters. No state matrix is concerned, and thus it is more straightforward from the physical essence viewpoint. The validity and accuracy are demonstrated by a 3-DOF numerical example for bridge deck model. Afterward, the 18 flutter derivatives of two exact bridge decks with representative streamlined and bluff sections are extracted. Detailed deterministic and stochastic vulnerability analyses on identification accuracy of modal parameters and flutter derivatives were conducted for the numerical model and two bridge decks. For the free vibration method, the potential uncertainties in aeroelastic parameter determination are investigated, and the causes of low accuracy of some flutter derivatives (e.g., H4*, A4*, P1∼4*) are attributed to the imperfection of the linear mathematical model, testing technique, and constraint conditions, and inherent low participation and/or coupling intensities of aeroelastic components. The aeroelastic characteristics and the influence of complex aerodynamic coupling on flutter performance of both streamlined and bluff bridge decks are examined and compared to unveil the mechanisms of two kinds of flutter.