Aerodynamic Interference Effects on Vortex-Induced Vibration of Two Parallel Railway- and Highway-Cable-Stayed Bridges with Triple-Separated Decks

In this study, wind tunnel tests were carried out to study the vortex-induced vibration (VIV) characteristics of two parallel long-span railway- and highway-cable-stayed bridges with triple-separated parallel decks. Furthermore, the effects of incoming wind direction, horizontal net distance, and vertical distance were considered. The maximum amplitude and lock-in interval wind velocity were analyzed to investigate the aerodynamic interference effects on the VIV of the main decks of the two parallel bridges. The results indicated that when the Quanzhou Bay railway bridge (QZRB) is located at the windward side (RW), the VIV occurs in both the main decks of the QZRB and the Quanzhou Bay highway bridge (QZHB). However, when the QZRB is located at the leeward side (RL), the VIV of the main decks of both the QZRB and the QZHB are suppressed. For RW cases, the maximum amplitude of the main deck of the QZRB is 114.1% higher than the case of the single main deck of the QZRB due to the aerodynamic interference effect, and the VIV of the main decks of the QZHB occurs both upstream and downstream. The maximum amplitude of the main decks of the QZRB and QZHB increases when the horizontal net distance is reduced. By changing the vertical distance, the maximum amplitude of the main deck of the QZRB increases. At the same time, the maximum amplitude of the main deck of QZHB-1 decreases, while QZHB-2 shows the opposite trend. For RL cases, the VIV of the main decks of the QZHB occurs only upstream (QZHB-2) and the main deck of the QZRB presents an obvious beat phenomenon. Increasing the horizontal net distance and changing vertical distance can weaken the beat phenomenon.