Sundøy Bridge

The Sundøy Bridge is a two-lane road bridge in Nordland County, Norway, designed as one of the world’s longest concrete cantilever bridges. The structure features a 298-meter main span and a total length of 538 meters. The high-level crossing provides a ship channel clearance of 43.5 x 80 meters in a region near the Arctic Circle known for severe wind conditions.

The structure is fully continuous with flexible piers and large foundations measuring 9 x 14 meters, founded on solid rock at elevations of -16.0 and -19.0 meters. Expansion joints are located at each abutment to accommodate movement in the harsh northern climate.

During design, both normal density and lightweight aggregate concrete were evaluated. Due to roadway curvature and rock topography constraints, high-strength lightweight aggregate concrete (LC60) incorporating Stalite Lightweight Aggregate was used in most of the main span, while the side spans utilized normal density concrete (C65). The reduced unit weight of the Stalite lightweight concrete improved span efficiency and structural performance. Compared to a design using normal density concrete in the main span, the selected solution resulted in savings of approximately 2,500,000 NOK.

Auxiliary piers were required during construction to stabilize the freestanding pier and balanced cantilevers. Alternative cable-stayed and suspension bridge concepts were also studied during preliminary design before selecting the cantilever configuration utilizing Stalite lightweight concrete.