Wind tunnel tests for soft flutter characteristics of double-deck truss girder

The application requirements of double-deck truss girders increase in bridge engineering with increase in urban traffic volume, and studying their soft flutter characteristics is helpful for improving their wind-resistant design level. Here, Yangsi Port Yangtze Bridge in Wuhan was taken as the study object, and wind tunnel tests were conducted for its segment model to measure soft flutter characteristics of its girder model under different working conditions, and compare similarities and differences of soft flutter forms under conditions of different wind speeds. The test results showed that double-deck truss girder reveals obvious soft flutter characteristics in tests, its flutter amplitude increases with increase in wind speed; under different wind speeds and 0° wind attack angle, soft flutter forms all are eccentric torsional motion; under 3° and 5° wind attack angles, soft flutter forms initially reveal typical bending-torsional coupled motion, with increase in wind speed, phase difference of bending-torsional coupled motion gradually decreases; when wind speed increases up to a certain value, bending-torsional coupled motion phase difference is zero, coupled flutter transfers to eccentric torsional one; in process of wind speed continuously increasing or decreasing, or under a constant wind speed, vibration amplitude of soft flutter is independent of initial excitations and related to a unique reduced wind speed, there are no phenomena that the same reduced wind speed corresponds to different amplitudes, or different reduced wind speeds correspond to the same amplitude; the occurrence mechanism of double-deck truss girder's soft flutter is explained from the view point of aerodynamic damping varying with variation of both reduced wind speed and flutter amplitude. © 2020, Editorial Office of Journal of Vibration and Shock. All right reserved.