The London skyline is becoming increasingly eclectic. The bulbous Gherkin (Foster + Partners), the towering Shard (RPBW) and the wind-turbine-topped, elongated-barcode that is the Strata tower (BFLS) will soon be joined by the Cheese Grater (RSHP), the Boomerang (Ian Simpson and Partners) and the Walkie-Talkie (RVA).
Aside from high-rise towers, there have been more eccentric and, in some cases, more loved additions that peek above the rooftops. The London Eye, at first implemented as a temporary attraction, has become one of the most recognisable modern additions to the capital’s silhouette. The Arcelor Mittal tower in the Olympic Park wriggles skywards in an ugly tangle of red. And now, a stone’s throw away from the sky-piercing crown of the O2 Arena, two spiralling towers have emerged from the banks of the Thames, and they have a pragmatic use as well.
At the end of 2009, a design competition to provide a river crossing linking the Greenwich peninsula to Albert Dock was launched by Transport for London, after its feasibility study had identified the need for a crossing.
Taking into account the flight path to City Airport, river traffic, the existing infrastructure, the proximity of the towers to the flood defences and a protected zone under the river, among other issues, the route across the river was tightly defined. ‘There was an incredible set of restraints – below ground, on the ground, in the river and in the air,’ says Oliver Tyler, director at Wilkinson Eyre who led the winning project team.
Having established that a cable car was the most feasible option, Wilkinson Eyre began to work within the parameters to create a configuration for the three towers the cable would pass between. ‘One of the key issues was the cable, which sags,’ says Tyler. ‘We had to achieve a clearance of 54m – the same as the Queen Elizabeth II Bridge in Dartford – to allow river traffic to pass unhindered.’ Height restrictions on the towers limited them to 90m (the height of the O2’s masts), so an optimum distance between the principal towers was designated by the cable-car specialist, Austrian firm Dopplemayr, along a straight line.
The river crossing can be read as two distinct elements: the docking stations on the north and south banks and the towers supporting the cable. ‘Our early concepts were about developing the stations as a lantern, predominantly glazed to have a presence night and day. We were also keen to exploit the mechanics of the system and the movement,’ Tyler adds.
The design of the docking stations is relatively simple in plan, expressing in simple materials and fairfaced concrete the radial movement of the cable cars as they pass through the building and return across the river.
A cantilevered landing pad occupies the first floor, where passengers will get on and off the cars. The glazing is arranged into a rhythmic acceleration that reflects the launch of the gondolas into the sky. During the day, people outside the station will see the mechanics and movement of passengers, and by night they will see an abstracted expression of the same movement in light and shadow.
On the ground floor, in the undercroft of the landing pad, is ticketing and the access gates. The south station will be slightly larger, as provision has been made there for storage and maintenance of the cars, and beneath it is designated as an exhibition and retail space.
‘We were very keen to develop something very visual that had its own identity. We looked at other similar schemes around the world and they tend to be very utilitarian and made of standard components,’ says Tyler. ‘Both stations should have a very similar language to each other and the three towers should be a family of details.’
The design team explored different methods of creating towers that were visually and structurally engaging, arriving at a compromise between a steel net structure, that is visually light, and a solid pylon.
‘We decided to deconstruct a solid tower into a series of steel ribbons, and developed an idea of creating a spiral held with helical ties,’ says Tyler. ‘This then splays out to pick up the cable car running gear at the top.’
The gaps in the structure reduce the visual intensity of the towers as well as helping to shed wind loading.
Wilkinson Eyre took the scheme to planning and prepared a tender package for the project’s construction. Architecture practice Aedas and construction firm Mace won the contract to build and operate the station, with Wilkinson Eyre retained by the client as a consultant on the project.
Since opening on 28 June 2012, passengers have been able to travel along the 1.1km route in five minutes inside one of 34 gondolas that each hold 8–10 people.
This addition to the London skyline will no doubt prove to be a popular tourist attraction, but on a practical, level it will ease the congestion on the area’s transport infrastructure, providing a route out of Greenwich that, on a busy night at the O2 arena with the Jubilee Line down, can prove very testing.