Influence of geometric details and external factors on the aeroelastic behavior of a single-box deck

The Julsundet Bridge, part of Norway's E39 fjord-crossing project, is set to become Europe's longest suspension bridge with a 1625-meter main span. Its single-box deck design, chosen for aerodynamic efficiency, approaches the critical flutter speed limit defined by Norwegian standards. This study investigates the bridge's aeroelastic stability through wind tunnel experiments and numerical analysis, focusing on the effects of geometry details, such as barriers and gantry rails, and external factors like snow accumulation. Wind tunnel tests conducted at the Politecnico di Milano evaluated various configurations to optimize stability without altering the deck's primary geometry. Snow accumulation, a significant factor in Nordic climates, was also simulated to assess its impact. Numerical multi-modal analysis complemented these experiments, providing insights into flutter mechanisms. Results indicate that the single-box deck is aerodynamically robust, with the circular gantry rails offering the best performance. However, snow accumulation substantially reduces stability, highlighting the need for maintenance protocols and monitoring systems. Vortex-induced vibrations were not observed under typical conditions, except during snow scenarios. This research demonstrates the feasibility of the single-box deck solution for the Julsundet Bridge and it provides practical insights for the design, maintenance, and operation of the bridge.