Degree of Freedom participated with Nuno arkitektur in the winning team of the architectural competition for a new movable footbridge in Norttalje, Sweden.
The task was to design a bridge that could be opened to allow for ship traffic and that would provide a natural connection and visual contact between the north and south quays. A bridge needed to harmoniously fit various landscapes, the old historic Sosietetsparken and the modern harbour environment.
The Norrtälje bridge is designed with both a structural logic and an architectural expression of high quality. The opening mechanism is conceived to be simple both in construction and in operation. The bridge is designed to be wide enough for cyclists and pedestrians to cross unhindered whilst also providing a meeting place lit up in the evening for views of the outer archipelago and the stars. The opening of the bridge for passing boats is a graceful motion, twisting asymmetrically in the harbour.
The bridge, curved in plan, consists of 4 spans of approximately 13m + 23.5m + 19m + 18.5m. The single spans adjacent to the north and south abutment are fixed whilst the two central spans are moveable and can rotate about a central support to open the bridge and create a shipping channel for larger vessels.
The deck comprises two 425mm deep steel box girders set back a constant distance from the deck edge. Due to the variable width, over the central span these merge to form a single box girder at the narrower part of the bridge and at the rotation support. In the open position the central section becomes a balanced cantilever about the central rotation support.
Steel plate ribs cantilever out from the box girders supporting longitudinal beams and the solid timber decking. Overall, the maximum depth of the deck section is limited to 500mm to meet both the clear height requirements of the shipping channel below and to comply with the limitation on deck slope from the lower south abutment of 5%. The chosen deck construction gives a lightweight, slender but torsionally stiff cross section.
Structural engineering during architectural competition.
