Three Degree-of-freedom Forced Vibration Method For Identification Of Aerodynamic Derivatives Of Bridge Decks

As a kind of important parameters describing the aerodynamic properties of bridge decks, aerodynamic derivatives are essential and exert a great role in predicting the flutter and buffeting performances of long-span bridges. In practice, the aerodynamic derivatives are often obtained via wind-tunnel tests of sectional model. According to different driving ways of vibration, the sectional model test methods can be classified into two major categories, i.e. free-vibration method and forced-vibration method. Compared to the free-vibration method, the forced-vibration method is regarded to have the following advantages: low noise level, low spread and high precision of identified results, and wide range of reduced wind speed. However, the forced-vibration method still remains at 2-DOF level because of the complication and high cost of the relevant test equipments, and the identified results based on the current theory and testing technique are not satisfied. In this connection, both the identification theory and testing technique of forced-vibration method are investigated comprehensively in this study. The major contents of the research are as follows:A new 3-DOF forced-vibration device has been developed for the identification of aerodynamic derivatives of bridge decks. Using this device, the sectional model can be forced to make a controllable 1-DOF harmonic oscillation in any one of the vertical, lateral and torsional directions, or a controllable 2-DOF or 3-DOF coupled harmonic oscillation in any two or three directions.The current frequency-domain method of state-by-state forced-vibration for the identification of aerodynamic derivatives is extended from 2-DOF (vertical and torsional directions) to 3-DOF (vertical, lateral and torsional directions). All the 18 aerodynamic derivatives can then be identified using the extended method. A frequency-domain method of 3-DOF coupled forced-vibration is proposed for first time for the identification of aerodynamic derivatives. By setting different vibration frequencies for the vertical, lateral and torsional vibration components respectively,...