In 2023, the team of schlaich bergermann partner, architects von Gerkan, Marg and Partners and WTM Engineers GmbH won the competition for the extension of the U4 underground line to the new Grasbrook district in Hamburg. The nearly 1,000-meter-long infrastructure project consists of a total of three sections: a U-Bahn railway bridge over the Elbe, a viaduct on the land side, and a two-story bridge with a suspended subway station at Moldauhafen that floats above the water.
In order to not visually disrupt the historic Freeport Elbe bridges (Freihafenelbbrücken), a lightweight and transparent network arch with dynamically flat steel arches and intersecting carbon hangers was chosen for the new Elbe bridge crossing – a unique and innovative solution in the field of arch bridge construction.
After crossing the Elbe, the arches merge into the V-shaped steel supports of the elevated viaduct. The distinctive V-shaped supports continue in a loose rhythm to the Moldauhafen subway station. There, the rhythm of the supports condenses into a truss bridge structure carrying two traffic levels. The first level is for pedestrian and bicycle traffic; from this level, users can also access the second level station platforms above. The frame structure for the glass station roof was developed logically from the extension’s V-shaped motif. The initial competition design included an integrated PV system for the roof. The individual modules were to be arranged from top to bottom in a single course. After the PV system was dropped, a print was developed that was modeled on the original course. Hamburg’s first subway station to float above the water, will initially be designed as the terminus of the U4 line, with an extension to Wilhelmsburg already in sight.
