Wind tunnel tests were conducted on an aero-elastic model of an open-type one-way tensioned membrane to investigate the aero-elastic instability mechanism of membrane structures. The structural response and wind velocities above the membrane were measured and analyzed. Complementary simulations were carried out to explain the interaction between the wind and the structure. The results indicate that the aero-elastic instability of the membrane is a kind of vortex induced vibration. This kind of instability is characterized by a sudden increase in the amplitude, or a sudden change in the dominant vibration mode, when the coming flow velocity exceeds a certain value. The vortices generated around the time-averaged deformation of the membrane lead to vortex induced vibration when the dominant frequency of the vortices is close to a certain natural frequency of the membrane. When the aero-elastic instability occurs, the frequency of the vortices is locked in by the structural vibration within a certain coming flow velocity range, and the total damping ratio of the vibration decreases dramatically and becomes nearly zero. Finally, the critical wind velocities are defined, and the reduced critical wind velocities corresponding to the first and second aero-elastic instabilities are 0.84 and 2.3 approximately.
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