Flow field analysis of self-sustained flutter of a wide-slotted bridge deck

Abstract

This study delves into the flutter mechanism of a 5,000 m bridge with a wide-slotted deck, finding that the motion is self-sustained and not violently destructive. The system damping ratio is not fixed, and only one stable orbit exists. High-resolution PIV experiments at an experimental wind speed of 10.5 m/s measured the static and dynamic flow fields on the windward and leeward decks. The static results showed leading-edge separation on the windward deck within the reference range, while separation on the leeward deck was difficult to observe. Dynamic testing identified instantaneous vortices around the windward/leeward deck at each phase, with no signs of vortices in the wind speed vectors at all phases after phase-averaging, indicating that the vortex drift hypothesis is not valid. The analysis of the streamline pattern revealed periodic variations in leading-edge separation size and reattachment length on the windward deck during the vibration process, while the leeward deck showed consistently inconspicuous changes. Further examination uncovered a peculiar behavior in the horizontal wind speed profile on the leeward deck during the vibration process, attributed to dynamic changes in the height difference between the windward and leeward decks during flutter. The study suggests that the unusual wind speed profile on the leeward deck is caused by the dynamic changes in height difference between the windward and leeward decks during the flutter process, resulting in additional wind loading. These findings shed light on the complex dynamics of bridge flutter and have implications for the design and maintenance of long-span bridges.