Butterfly Bridge
Bridges are places that offer new perspectives on the city, spectacular views of the water that reveal the cityscape. The bridges are elements that are part of the urban landscape in a natural way.
Through their simplicities, they form a contrast with the monumental buildings. The bridges designated for pedestrians and cyclists offer a maximum of transparency and lightness.
The very specific situation demand an original form for this foot- and cycle bridge: Three decks connect the different banks. Fixed on a common platform, apron fixed the other two openings for passing sailboats. When both doors are open at the same time, they form a butterfly, a beautiful figure, which is spectacular for its size.
The link across Christianshavns Kanal and Trangraven is designed as three linear bridge spans that meet above the water’s surface in a star shape. The canal bridge design is adapted to the individual canal scenario.
Two of the spans can be opened independently of each other. When the moving spans are up they serve as barriers which means that the bridge always functions to and from Islands Plads.
The main structure of the steel bridge consists of a single-web, continuous T-beam. The beam web, which extends over the entire bridge, is built of a trapezoidal, for reasons of corrosion protection hermetically welded hollow section. The bridge deck is composed of an orthogonal anisotropic plate construction.
The moveable superstructure is formed of two individual bridge flaps. A counterweight to support the process of motion is not provided. The clear opening width is 15 m, the length from the pivot point to the flap tip is 23.3 m.
The width of the bridge cross-section is 7.9 m and the cross-sectional height varies at the bridge top from 0.5 m to 1.7 m at the junction of the cylinder with the superstructure.
The longitudinal beam widens from the axis of rotation starting at a width of 40 cm upwards in order to achieve the structural effective height of 1.7 m above the attachment point of the hydraulic cylinder. Towards the flap tip the construction height decreases again to pass to the standard cross-section.
The anchor point of the hydraulic cylinder is about 5 m from the axis of rotation. The axis of rotation and its support are part of the central pedestal. The hydraulic cylinders are stored on the pile cap of the center landing. When closed, the flap tip rests on the opposite shore-side bridge.
The structural system of the bridge flaps corresponds in a closed state to a single-span beam with a supportive structure which is restrained on one side (platform side) and pinned and supported on the other side (ramp to the shore). In an open state the bridge flap corresponds to a clamped cantilever.