Identification Method Of Free Coupled Vibration For Aerodynamic Derivatives Of Bridge Decks

Flutter and buffeting are two key issues in the research of wind-resistant performance of long-span bridge. As one of the important sections in the flutter and buffeting researches, the identification of aerodynamic derivatives is rather difficult and has not been perfectly solved yet.The fundamental methods for flutter analysis and the current status of aerodynamic derivative identification are reviewed at first in this thesis. Then, the method for the aerodynamic derivatives of bridge decks and the corresponding testing technique are studied based on a dynamic force-measurement test of a free coupled-vibration sectional model. The following major achievements are then obtained:1. A free coupled-vibration force-measurement frequency-domain method is proposed for the identification of aerodynamic derivatives, and the corresponding identification software is developed.2. A free coupled-vibration force-measurement time-domain method is presented for the identification of aerodynamic derivatives, and the corresponding identification software is developed.3. Trough a numerical simulation test, the aerodynamic derivatives of an ideal flat plate are identified using the proposed free coupled-vibration force-measurement frequency-domain and time-domain methods, and good agreements are found between the identified results and the theoretical ones. The applicability and feasibility of the developed methods are thus verified preliminarily.4. A new testing technique for the measurement of aerodynamic self-excited forces acting on a sectional model is developed with the function of excluding inherently the resiliences and damping forces of suspending springs using four beam-type strain force balances of one-dimension directly mounted on the vibrating model.5. Trough a wind tunnel test of sectional model, the aerodynamic derivatives of a quasi-flat plate with a width-to-depth ratio of 22.5 are identified using the proposed free coupled-vibration force-measurement frequency-domain and time-domain methods. The identified results are found satisfied by comparing with the theoretical solutions and those identified using the forced-vibration method. The applicability and feasibility of the proposed methods are further verified.