Abstract:In this paper, the flutter performance of the streamlined box girder section of Nanjing Yangtze River 4th Bridge is tested in detail under different wind angles of attack through section model free vibration wind tunnel test. The evolution law of the nonlinear characteristics of flutter response with wind speed and wind angle of attack is investigated. The dynamic mechanism of flutter response varying with wind speed and wind angle of attack is discussed Results show that at negative angles of attack, the response of the system depends on the initial amplitude due to the characteristics of multiple unsteady limit cycles decreasing with the increase of wind speed, consequently, the flutter performance decreases sharply with the increase of initial excitation. At positive wind angles of attack, the flutter response of the system is characterized as typical soft type flutter because the multi-steady limit cycles increase with wind speed. At high wind speed, the system response is characterized as hard flutter due to the disappearance of limit cycle, which is independent of initial amplitude. Finally, the dynamic mechanism of the flutter patterns of the system at different wind angles of attack is explained from the evolution law of modal damping with amplitude.
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