|
Swiss Re Tower by Foster and Partners The outside of the building consists of 260,000 square feet (24,000 square meters) of glass panes. But the idea behind the overall form is to forge a connection with nature. Although dubbed "Gherkin," the spiral in its shape more resembles a pinecone. The external diagonal steel structure uses triangular forms to be inherently strong, permitting a flexible column-free interior space. The building's height was made feasible by the use of a peripheral "diagrid," in which all the steel elements subtly interlock. The exterior cladding consists of approximately 5,500 flat triangular and diamond-shaped glass panels, which vary in size at each level. Success after False Starts In 1992, an Irish Republican Army bomb destroyed the historic Baltic Exchange in St. Mary Axe. This had been the last Edwardian trading floor in London. In 1995, the exchange sold the site to developer Trafalgar House, which set out to build over 485,000 square feet (45,000 square meters) of office space. Trafalgar House employed Foster and Partners to design the new building. In 1996, the first design, the 2600-foot- (800-meter-) high Millennium Tower was submitted for approval and then withdrawn. Reinsurance company Swiss Re subsequently bought the site, inheriting its planning permission, and retained Foster and Partners to design its new London headquarters to replace its five dispersed locations throughout the City. Construction started in 2002 and was completed two years later. The tower's worthiness as an architectural icon is made evident by the prestigious award, but local attitudes are mixed. It is a symbol for London, a recognized addition to the city's high-profile skyline that includes St. Paul's Cathedral, which speaks volumes for its impact and acceptability. However there are those who see the new tower not as a bold intervention in the city's streetscape but as a building out of context with its surrounds, a reaction to commercialism of the city. Although the building's shape has no obvious reference point from the existing streetscape, the tower now seems firmly established. Its contextual inhabitation has been the result of extended negotiations with city planners before permission was obtained. The architects skillfully convinced the establishment that it was time for a change. This is an often neglected aspect of the architect's work but worthy of credit in this instance. To negotiate with the bureaucracy and build such a novel form is an amazing achievement. Spirals of Glass The tower's glazing wraps around a diagonally braced structure, with a new public space of around 7500 square feet (694 square meters) of retail in a double-arcade on the ground floor. Entrances to the building are through high triangular archways cut out of the diamond grid of the facade. The building provides 450,000 square feet (41,810 square meters) of net office space. At the edge of each floorplate is a spiral atrium, created by "twisting" each successive floor. This allows natural ventilation — although air-conditioning is also incorporated — by taking advantage of the large pressure differentials that draw air in through horizontal slots in the cladding. At every sixth floor, the atria feature gardens that control and purify moving air and divide the building into fire safety zones. The balconies on the edge of each light-well provide strong visual connections between floors and create a natural focus for communal office facilities. The envelope at the office areas consists of a double-glazed outer layer and a single-glazed inner screen that sandwich a central, ventilated cavity containing solar-control blinds. These cavities act as buffer zones to reduce the need for mechanical heating and cooling and are ventilated by exhaust air drawn from the offices. >>> Discuss this article in the Architecture Forum...
|
|
|
