Determination of Flutter Derivatives for the Great Belt Bridge

A new method which combines control theory and system identification techniques has been used to extract flutter derivatives from section model tests for the Great Belt East Bridge. Tests were conducted by exciting the section model simultaneously in vertical and torsional modes of vibration. Tests were primarily conducted in smooth flow for various ratios between vertical and torsional frequencies of vibration. Limited testing was also conducted in turbulent flow and for different angles of attack. The analysis technique described allowed extraction of seven aerodynamic derivatives including coupled motion derivatives from a simple set of tests.This paper describes the control theory and system identification approach used and discusses the limitations encountered. Results are compared with flutter derivatives obtained by other researchers. The method offers a reasonably robust technique for automating the process of extracting aerodynamic derivatives from recorded time histories of coupled vertical and torsional motion.