Crown Bridges

The competition asked for a link, the Crown Bridges (Kruunusillat), between Kalasatama and Kruunuvuorenranta in Helsinki. Kalasatama is a new city district located on the eastern side of Helsinki’s city centre, while Kruunuvuorenranta is a residential area currently being designed three kilometres further to the east, behind the Kruunuvuorenselkä sea area.

The main users of the link are trams, cyclists and pedestrians. The traffic connection has also to accommodate service and emergency vehicles. The competition task includes the conceptualisation and investigation of the Kalasatama, Korkeasaari (the Zoo island), Palosaari and Kruunuvuorenranta traffic connection. The main emphasis of the task is the design of the connection between Korkeasaari  and Kruunuvuorenranta, a total span of approximately 2km.

The proposal has an elegant and curvy alignment which with one gesture links the city centre of Helsinki to the Zoo and the new urban development of Kruunuvuorenranta. The bridge does not land on any intermediate island and still connects all the various town parts on the route. The main structure consists of as a pre-stressed concrete truss bridge which expands in height to the middle of the bridge where the major spans are placed.

The main idea is that the bridge, due to weather conditions and to its length, is essentially a tram bridge between Kruunuvuorenranta and Korkeasaari (approx. 2km), while it becomes more of a pedestrian and urban bridge between Korkeasaari and Kalasatama (approx. 350m). Coherently with this idea the main bridge offers a solution that protects the tram tracks from the snow over the 2km path, allowing the tram to speed as much as possible even in winter time. The pedestrian and bicycle decks descend to the same level of the tram deck only towards Kruunuvuorenranta and between Korkeasaari and Kalasatama where the presence of stops will force the tram to decrease its speed.

The top deck (for bicycles and pedestrians) is thought as a linear park with facilities for people to appreciate the views and rest, but even so it is quite unlikely that it will be used by pedestrians, independently from weather conditions, due to the length of the crossing. Bicycles might be more frequent on the bridge although mainly in summertime. Some cross-country skiers might use the bridge during winter time. In general the people’s presence between Kruunuvuorenranta and Korkeasaari is estimated to be minimal, while it will be elevated between Korkeasaari and Kalasatama.

I worked on all phases, particularly in the initial concept phase by sketching alternative for the double-decker solution. I worked on all 2D drawings in the initial phase, defining the alignement and checking the first 3D model solutions. I have also set up the camera movements for the 3D animation. In addition I realized a model in scale 1:500 for presenting the project (4m long!) using a mixed technique of laser-cut wood and polymethyl methacrylate pieces together with 3D printed elements.

Due to the use of concrete, the structural elements can be freely sculpted for architectural purposes and shaped to follow the flow of forces through the truss. This durable and efficient design is achieved by employing ultra-high performance concrete (UHPC) for the superstructure. This material exhibits a compressive strength near the yield stress of structural steel but with a specific weight of only about a third so that it is possible to build a lightweight and slender bridge as if we were designing it in steel, but with lower maintenance costs.

Developed as part of a small team while working at Zwarts & Jansma Architects in Amsterdam, the Netherlands.

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