The Shard at London Bridge Quarter is the tallest building in Western Europe. The 310m high iconic tower has redefined the London skyline and is already an international symbol for London, hosting 8,000 workers, residents and hotel guests a day and 1m public visitors a year.
Delivering a vision of a 'vertical town', swiftly and safely
The Shard is a 1.2m sq ft mixed use ‘vertical town, with ground floor retail, more than 600,000 square feet of office space on 25 floors, three floors of restaurants and bars, a 17-storey hotel, 13 floors of apartments and a triple height viewing gallery as well as a near open-air viewing platform on level 72. It’s crowned with a steel-framed pinnacle clad with shards of glass designed to blend into the sky.
Delivering Europe’s tallest tower rapidly and safely required engineers WSP to work closely with architect Renzo Piano, developer Sellar Property and contractors Mace to develop innovative new construction techniques. And to be achieved on a relatively tiny site of just over 1 acre.
The result is a world class building, constructed safely over just 44 months adjacent to one of London’s major transport hubs, London Bridge Station.
World first top-down construction technique
The Shard’s tapered form is possible due to its innovative three part build. At the building’s heart is a 72-storey concrete core, but as the tower rises, there are three separate structures – a steel-frame building for the first 40 floors, a post-tension concrete frame up to level 72, and then a steel spire to complete the shape to the equivalent of level 95.
The numbers were huge: to excavate the three basement levels, 60,000 tonnes of spoil was removed, the steel frame is made of 15,000 pieces and weighs almost 12,000 tonnes. The glass curtain walling comprises 10,500 glazing units and covers 56,000 square metres.
Top-down construction allowed the first 23 storeys of the concrete core and much of the surrounding tower to be built before the basement had been fully excavated. This technique was a world first and saved four months on the complex programme.
Innovative use of materials
The greatest concern for the designers of tall buildings is to control how much they sway in the wind and specifically to minimise lateral acceleration. The use of concrete rather than steel from level 41 to level 69 has provided greater damping at these levels, absorbing the energy of the wind.
The weight of the concrete meant that a tuned mass damper – a weight with very large shock absorbers – from a previous version of the design could be eliminated. This had taken up a whole residentialfloor of the building, which could not be sold. WSP’s solution therefore further enhanced values for the client.
Using concrete also meant that the overall floor depth could be shallower, allowing for an extra two floors within the total height.
WSP was also able to minimise the weight of materials within the structure. The base slab right at the bottom of the basement measures just 3m at its thickest point. By keeping the base slab as thin as possible, it saved excavation and concrete and reduced the carbon dioxide released into the atmosphere.
Prefabrication to minimise the risks of working at height
Assembling the 500-tonne, 66-metre steel spire 300m above ground required a new engineering approach from WSP and contractors Mace. The strategy was to prefabricate and pre-assemble at ground level to ensure no risk was taken by assembly at such an unprecedented height. Preparation for installation included extensive training and detailed lifting plans meaning that the Spire was lifted into place on schedule without any serious incidents and has become an exemplar case study for high buildings.
The team’s commitment to safety ensured the project logged a million RIDDOR-free hours, no mean feat for the highest building ever delivered in the UK.
Regeneration without disruption
The Shard was intended to regenerate and energise South London and the team worked with the client to realise that aspiration at every stage. The development promoted sustainable travel by including only 48 car parking spaces and including a major refurbishment of the adjacent London Bridge station, which handles 55m passengers annually.
Passenger satisfaction scores actually increased by 7% during construction and this is testimony to collaborative teamwork and local stakeholder management.