The leap across the Elbe arrives with three new structures
Extension of the U4 in Hamburg opens up Grasbrook and Veddel
The team of schlaich bergermann partner (sbp), von Gerkan, Marg and Partners Architects (gmp) and WTM Engineers have won the two-stage competition for the extension of the U4 subway line to the new Grasbrook district in Hamburg.
The nearly 1,000-meter-long infrastructure project consists of a total of three sections: a 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. Due to the unity of the design, the proposal convinced the jury with its seamless transitions between the three sections and the integrated connection of the U4 line.
At the beginning of 2022, Hamburger Hochbahn AG invited eight pre-qualified teams to participate in the interdisciplinary design competition for the extension of the U4 from Elbbrücken to Grasbrook. Of the total of eight entries from international planning consortia, the selection committee decided in favor of the joint design by sbp, gmp and WTM after the second stage with only three participants.
The extension of the U4 line across the Elbe links the new Grasbrook district on the southern bank of the Norderelbe, which is currently under development, to Hamburg’s HafenCity. This means that the long-planned “leap across the Elbe” is now a reality. The new Moldauhafen stop will initially be designed as the terminus of the U4 line, with an extension to Wilhelmsburg already in sight.
In order to not visually disrupt the historic Freeport Elbe bridges (Freihafenelbbrücken) in the first section, a lightweight and transparent network arch with dynamically flat steel arches and intersecting carbon hangers was chosen for the new Elbe bridge – 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, which stand in the direction of travel. The distinctive V-shaped supports continue in a loose rhythm to the Moldauhafen subway station. There, the rhythm of the supports condenses into a bridge structure as a truss from the two traffic levels. The frame structure for the station roof develops logically from this motif. Hamburg’s first subway station to float above the water is characterized by a semi-transparent photovoltaic glass facade. At night, a warm-toned lighting concept that is self-sufficient thanks to the energy facade provides travelers with a welcoming orientation.
Sven Plieninger, board member of sbp se, comments on the win as an important contribution to the neighborhood development of Hamburg’s HafenCity:
“We are very pleased that we have now also won the extension of the U4 as a continuation of the Elbbrücken subway and commuter rail station already planned with gmp. With our design, we are not only shaping the cityscape of the growing HafenCity, but with the carbon network arch and the energy facade, we are also setting an important example in terms of innovation and sustainability in the new Grasbrook district.”
Nikolaus Goetze, partner at gmp:
„It is a great challenge to be able to realize the leap across the Elbe from the Elbbrücken bridges to Moldauhafen together with sbp and WTM in one piece with the continuation of the U4. At this central networking point of Ham-burg’s urban silhouette, we feel equally committed to tradition and innovation. The new Moldauhafen station will be – figuratively speaking – the first station in Hamburg to float entirely above the water. As the second station on the U4 line to be located above ground, it also clearly shows its kinship with the Elbbrücken subway station.”
Gerhard Zehetmaier, partner of WTM Engineeers:
“The development of a future-oriented mobility for Hamburg is very close to our hearts. Therefore, we are pleased to be part of the U4’s leap across the Elbe. Together with sbp and gmp, we want to create a milestone for sustainable and user-friendly infrastructure in a growing metropolis: with creative and innovative ideas – and with a lot of heart and soul.”
