Pedestrian and cyclist bridge over Vistula river
Warsaw, 2nd prize
The new pedestrian and cyclist bridge is joining two banks of the Vistula River at the height of Karowa Street and Okrzei Street, connecting the districts Powisle and Praga in the center of Warsaw.
The left bank of the river is highly urbanized and characterized by a mix of historical and modern urban tissue. Museums, cultural institutions and educational facilities are located in the next proximity. A new, recently opened boulevard creates a mondaine waterfront and a new strolling promenade along the river, becoming a new center for social and cultural events.
The right bank of the river has a different character: slopes descending towards the water are covered with dense vegetation and are home to a variety of fauna and flora. Praga, a former workers’ district with a relatively bad reputation, has been undergoing recently a transformation into a vibrant and diverse area.
The proposed bridge works as an urban mediator between these two different worlds, starting straight as a continuation of the axis of Karowa Street and then winding gently towards Okrzei Street. Four ramps, two on the west bank and two on the east bank, work as connectors reaching out from the main axis of the bridge up and down along the river. The bridge and its ramps merge smoothly with the existing infrastructure, obeying the linear organization of the boulevard with its pavilions along the Wisłostrada on the left bank, and connecting to the natural environment on the right bank. Although it improves the mobility by providing a shortcut in transfer between distinct city districts, the bridge is in fact about a slow movement, about the enjoyment of change of surrounding when transitioning from one urban area to another.
Team:
Dipl. Arch. ETH SIA Anna Jach, Zurich, Switzerland
Dipl. inż. arch. Zuzanna Krzyżanska
Dipl. inż. arch. Antoni Kęszycki
Schnetzer Puskas Ingenieure AG
Dipl. Arch. ETH SIA Anna Jach, Zurich, Switzerland
Dipl. inż. arch. Zuzanna Krzyżanska
Dipl. inż. arch. Antoni Kęszycki
Schnetzer Puskas Ingenieure AG
siteplan
Materialisation
The bridge is essentially a slender metal band of weathering steel. The main structural element are the side beams, consisting of a top- and bottom flange and a large sheet of perforated corten steel, varying in height, related to the span of the bridge.The side beams are held by cross connecting steel beams with a walkway on top of them. The perforation openings are organized in a gradient, related to the bridge section spans - in the areas above the columns the openings are sparse while getting denser towards the middle of the section. The alignment of the openings reacts to the distribution of the shear forces within the railing. The openings add an additional value to the bridge: they enable views through the railing down to the river and to the surroundings, which is particularly useful for smaller children (and their parents), as the railing is relatively high (1.20m).
Lighting
A linear system of lighting emphasizes the slender silhouette of the bridge. It consists of two LED stripes: one at the bottom of the outer side of the bridge railing, and one on the inner side of the bridge. The former follows the slight curvature of the bridge and yields a reflection in the river during the night, marking the bottom edge of the bridge for the upcoming ships.
The latter is integrated the handrail and lightens up the inner sides of the railing and the walkway. Illuminated corten steel appears golden, resulting in a warm shimmering, and the lighting effect of both stripes is combined through the openings in the balustrade, creating a constellation of lighting points amplified by the reflections in the water. In order to improve the visibility of the bike lane, reflective dots are inlayed at the edges of it.
Construction Progress
A smooth construction sequence is reached by designing the bridge in a way it can be elementwise prefabricated. Steel is a very lightweight and extremely strong building material, but it is not as cheap as concrete. Prefabrication of single elements, that can be put together on site easily, reduce the building cost to a minimum and allow a weather independent and fast construction progress.
During the prefabrication process, the foundations of the bridge can be built. Even the complicated foundations in the river are optimized for a cost efficient and fast fabrication. First a watertight sheet pile wall is rammed into the riverbed with the rammer standing on a float. The sheet pile wall is then used as a foundation for a small drilling machine, which creates the micropiles under the future foundation. Thereafter the water is pumped out of the sheet pile box, which needs to be braced against the waterpressure. As soon as no more water is in the box, the excavation of the riverbed can start. The micropiles’ heads are built in the pile cap that is created. The fabrication of the whole concrete foundation follows after that and at the end, the sheet piles can be pulled out again. The ROR profiles can be erected then on top of foundation and after that, everything is ready for the prefabricated elements to be mounted.
