Monday, December 20, 2010

30 St. Mary Axe

30 St Mary Axe, also known as the Gherkin and the Swiss Re Building, is a skyscraper in London's main financial district, the City of London, completed in December 2003 and opened at the end of May 2004. With 40 floors, the tower is 190 metres (623 ft) tall. and stands on the former site of the Baltic Exchange building, which was severely damaged on 10 April 1992 by the explosion of a bomb placed by the Provisional IRA

After the plans to build the Millennium Tower were dropped, the current building was designed by Norman Foster, his then business partner Ken Shuttleworth and Arup engineers and was erected by Skanska in 2001–2003.

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 reinsurance company, who had the building commissioned as the head office for their UK operation. The tower is sometimes known as "Swiss Re Tower", although this name is not official.

The building uses energy-saving methods which allow it to use half the power 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.
Architects limit 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.

The base of the towerOn 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.
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.

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