Effect of gap distance on vortex-induced vibration in two parallel cable stayed bridges

This study was focused on the vortex-induced vibration (VIV) in parallel-disposed twin cable-stayed bridges. A series of wind tunnel tests were carried out to investigate the gap distance between two bridge decks and its effect on VIV. The gap distances examined covered a wide range of from one to twenty times the depth of the upstream deck. The amplitudes of VIVs in both decks were estimated using the variations in wind velocity. Particle image velocimetry (PIV) tests were performed to identify streamline changes between two decks for different gap distances. Also, the distribution of the swirling strength of the generated vortices was evaluated based on the velocity data obtained from PIV testing. According to the research results, gap distances of five to seven times the depth of the upstream deck critically affected the interactive VIV in two parallel cable-stayed bridges. The vulnerable gap distance was closely related to the moving distance of one vortex during a period of oscillation of the deck.