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The building THE GHERKIN is an iconic symbol of London and is one of the city's most widely
recognized examples of contemporary architecture.
30 St Mary Axe (widely known informally as The Gherkin and previously as the Swiss Re
Building) is a commercial skyscraper in London's primary financial district, the City of London.
It was completed in December 2003 and opened in April 2004. With 41 storeys, it is 180 meters
(591 ft) tall and stands on the former site of the Baltic Exchange, which was extensively
damaged in 1992 by the explosion of a bomb placed by the Provisional IRA in St Mary Axe, the
street from which the tower takes its name.
After plans to build the 92-storey Millennium Tower were dropped, 30 St Mary Axe was
designed by Norman Foster and Arup Group and it was erected by Skanska, with construction
commencing in 2001.
The building stands on the former site of the Baltic Exchange, the headquarters of a global
marketplace for ship sales and shipping information.
The United Kingdom government's statutory adviser on the historic environment, English
Heritage, and the City of London's governing body, the City of London Corporation, were keen
that any redevelopment must restore the building's old façade onto St Mary Axe. The Exchange
Hall was a celebrated fixture of the ship trading company.
After English Heritage later discovered the damage was far more severe than initially thought,
they stopped insisting on full restoration, albeit over the objections of the architectural
conservationists who favoured reconstruction. The Baltic Exchange sold the land to Trafalgar
House in 1995. Most of the remaining structures on the site were then carefully dismantled, the
interior of Exchange Hall and the façade were preserved, hoping for a reconstruction of the
building in the future. Parts of its stained glass are displayed at the National Maritime Museum.
The tower's topmost panoramic dome, known as the "lens", recalls the iconic glass dome that
covered part of the ground floor of the Baltic Exchange.
The Gherkin name was applied to the current building at least as far back as 1999, referring to
that plan's highly unorthodox layout and appearance.
THE ARCHITECTURAL FORM:
The shape of the tower is influenced by the physical environment of the city.
The smooth flow of wind around the building was one of the main considerations.
A net office floor area within the building of around 500,000 ft2 (46,450 m2).
The enhancement of the public environment at street level, opening up new views across the
site to the frontages of the adjacent buildings and allowing good access to and around the
Minimum impact on the local wind environment.
Maximum use of public transport for the occupants of the building.
Flexibly serviced, high specification ‘user-friendly’ column free office spaces with
maximum primary space adjacent to natural light.
Good physical and visual interconnectivity between floors.
Reduced energy consumption by use of natural ventilation whenever suitable, low façade
heat gain and smart building control systems.
3. Twenty-First Floor Plan 4. Fortieth Floor Plan
5. Office Modules
6. Light Well
7. Private Dining
8. Elevator / Stair
30 St Mary Axe has a radical approach - technically, architecturally, socially and spatially.
Idea of having a city within a city.
An instantly recognizable addition to the city’s Skyline.
The site was special because it needed development, was not on any of the "sight lines"
(planning guidance requires that new buildings do not obstruct or detract from the view of St
Paul's dome when viewed from a number of locations around London), and it had housed the
The plan for the site was to reconstruct the Baltic Exchange. GMW Architects proposed a new
rectangular building surrounding a restored exchange—the square shape would have the type of
large floor plan that banks liked. Eventually, the planners realised that the exchange was not
recoverable, forcing them to relax their building constraints; they hinted that an "architecturally
significant" building might obtain a favourable reception from city authorities. This gave the
architect a free hand in the design; it eliminated the restrictive demands for a large, capital-
efficient, money-making building, whose design was per the client's desire.
Swiss Re's low level plan met the planning authority's desire to maintain London's traditional
streetscape with its relatively narrow streets. The mass of the Swiss Re tower was not too
imposing. Like Barclays Bank's former City headquarters in Lombard Street, the idea was that
the passer-by in neighbouring streets would be nearly oblivious to the tower's existence until
directly underneath it.
Design and construction
The building was constructed by Skanska, completed in December 2003 and opened on 28 April
2004. The primary occupant of the building is Swiss Re, a global reinsurancecompany, which
had the building commissioned as the head office for its UK operation. The tower is thus
sometimes known as the Swiss Re Building, although this name has never been official and has
more recently fallen out of favour since the company's main headquarters is in Zurich and the
Gherkin name has become more popular.
The building uses energy-saving methods which allow it to use half the power that a similar
tower would typically consume. Gaps in each floor create six shafts that serve as a natural
ventilation system for the entire building even though required firebreaks on every sixth floor
interrupt the "chimney." The shafts create a giant double glazing effect; air is sandwiched
between two layers of glazing and insulates the office space inside.
30 St Mary Axe under construction
Architects promote double glazing in residential houses to avoid the inefficient convection of
heat, but the tower exploits this effect. The shafts pull warm air out of the building during the
summer and warm the building in the winter using passive solar heating. The shafts also allow
sunlight to pass through the building, making the work environment more pleasing, and keeping
the lighting costs down.
The primary methods for controlling wind-excited sways are to increase the stiffness, or increase
damping with tuned/active mass dampers. To a design by Arup, its fully triangulated perimeter
structure makes the building sufficiently stiff without any extra reinforcements. Despite its
overall curved glass shape, there is only one piece of curved glass on the building—the lens-
shaped cap at the very top.
On the building's top level (the 40th floor), there is a bar for tenants and their guests featuring a
360° view of London. A restaurant operates on the 39th floor, and private dining rooms on the
38th. Whereas most buildings have extensive lift equipment on the roof of the building, this was
not possible for the Gherkin, since a bar had been planned for the 40th floor. The architects dealt
with this by having the main lift only reach the 34th floor, and then having a push-from-below
lift to the 39th floor. There is a marble stairwell and a disabled persons' lift which leads the
visitor up to the bar in the dome.
here where it opens into the office floor at the base of one of the six-story atriums, the Abluft enclosure
sandwiches blinds and encased diagrid struts between the exterior curtain wall and an inner curtain wall
of rectangular glass sheets
The building is visible over long distances: from the north, for instance, it can be seen from
the M11 motorway, some 32 kilometres (20 mi) away, while to the west it can be seen from the
statue of George III in Windsor Great Park.
The mixed-mode ventilation that would allow the building to be cooled mechanically or through
natural ventilation depending. The Gherkin is enclosed by a unique curtain wall that combines
two systems. For most of its circumference on any given office floor, the building is encased by
an exterior curtain wall of clear diamond-shaped double-glazed panels as well as an interior
curtain wall of rectangular single-glazed panels fitted with blinds. In this Abluft or exhaust
façade, heat that builds up in the airspace between the two curtain walls is exhausted to the
outside by vents at the top of each one- or two-story zone. Where the enclosure adjoins the
spiraling atria, the interior curtain wall is omitted and the exterior curtain wall is tinted to reduce
solar heat gain as well as fitted with some operable windows that tilt open to admit fresh air.
When weather permits, a computerized building management system can selectively open these
windows, using the pressure differentials at atria thirty degrees apart around the façade to draw
air in and through the building.
In April 2005, the press reported that a glass panel two-thirds up the tower had fallen to the plaza
beneath. The plaza was sealed off but the building remained open. A temporary covered
walkway, extending across the plaza to the building's reception, was erected to protect visitors.
Engineers examined the other 744 glass panels on the building. The cost of repair was covered
by main contractor Skanska and curtain-wall supplier Schmidlin (now called Schmidlin-TSK
AG). Since its completion, the building has won a number of awards for architecture.
Plan view from a simulation of air flow and velocity through the sixth floor was among the many
documents generated by environmental consultants BDSP during the design of 30 St Mary Axe to model
the building’s environmental performance. BDSP, Swiss Re HQ, 2009. Presentation.
Like the previous image, this perspective view of a simulation of air velocities in Atrium 6 framed
expectations about energy consumption at 30 St Mary Axe. BDSP, Swiss Re HQ, 2009. Presentation.
FACTS AND FIGURES DIMENSIONS:
Height to top of dome: 179.8 m
Height to highest occupied floor level: 167.1 m
Number of floors above ground: 40
Number of basement levels: single basement across whole site
Largest floor external diameter (lvl 17): 56.15 m
Site area: 0.57 hectares (1.4 acres)
Net accommodations areas:
Office 46,450 m2
Retail 1,400 m2
Office floor-floor: 4.15 m
Gross superstructure floor area (incl. lightwells): 74,300 m2
Tower Structural Steelwork
Total weight of steel (from Arup Xsteel model): 8,358 tonnes of which:
29% is in the diagrid
24% core columns
Total number of primary steel pieces: 8 348
Total length: 54.56 km
Diagrid column sizes:
Ground – level2: 508mm f, 40mm thick
Level 36–38: 273mm f, 12.5mm thick
Hoop design tension at level 2: 7 116 kN
Perimeter column maximum design load: 15,460 kN
Core column maximum design load: 33,266 kN
Foundations 750mm diameter straight-shafted piles into London Clay
Number of piles: 333
Total length of piles: 9 km
Total design capacity: 117,000 Tonnes
The tower is aerodynamically designed to reduce wind load on the structure, whilst the
lower part tapers so that wind wraps around the tower.
The six fingers of accommodation on each floor, configured with light wells in between,
maximize daylight penetration.
The façade design with advance glazing technologies, ventilated cavities and blinds ,
provides up to 85% solar protection.
Gas is the main fuel used hence it will only generate half the carbon emission.
Overall energy serving is up to 50%.
2004 RIBA Stirling Prize . For the first time in the prize's history, the judges reached a
unanimous decision. In December 2005, a survey of the world's largest firms of architects
published in 2006 BD World Architecture 200voted the tower as the most admired new building
in the world. However, Ken Shuttleworth, who worked for Foster and Partners on the design of
the building, said in 2011 that he believed the style was now out-moded: "I was looking at the
glass all around and [thought], 'Why on earth did we do that?' Now we would do things
Working on this project, we have studied about the various energy efficiency
methods and techniques that have been used in The Gherkin Tower building.
This report will always help me in my design projects and help me in
contributing to the environment. We should also try our best to save energy
and lessen the carbon foot print of all the designs we do.