is soon to start work on the construction of his Tour Sans Fin, a slim, cylin-
drical office tower that will rise 1,400ft (425m) from its confined base at La Defense.
In Britain, the tallest building is the bulky stainless-steel-clad Canary Wharf Tower, punching its way 850ft (260m) into the London Docklands sky. Very tall buildings are unpopular in Britain - the stunted office towers built in the past 40 years are rather miserable things, while even the British Telecom Tower seems, at 400ft (120m) or so shorter than the Eiffel Tower, half- hearted. This is odd, not only because pencil-slim towers are much kinder to city skylines than corpulent office blocks, but also because England has a long and honourable tradition of reaching for the sky in stone and steel. Hundreds of medieval and Victorian English churches are capped with sky- piercing spires, while the 14th-century spire of Salisbury Cathedral reaches an astonishing 404ft (123m).
Paris so far has only two notably tall buildings - the Tour Montparnasse, a grim block looming above Montparnasse station and the restaurant La Coupole, and the Eiffel Tower itself. But Barcelona has the triffid-like steeples of Antonio Gaudi's still incomplete Expiatory Temple of the Holy Family (the Sagrada Familia) and is otherwise surrounded by several highly impressive industrial chimneys, themselves wrapped round by several mountainous ridges. On the top of one of these is the facade-thin church fronting the old Tibidabo amusement park, reached by tram and funicular from the city centre; on another - Collserola - is the new telecommunications tower designed by Foster Associates. The Torre de Collserola is one of those structures that draws visitors like a magnet. It has been built not just as a telecommunications mast, but as a self-conscious 'monumental technological element for the 21st century' (these are the words of the city council, not the British architects), standing in a national park overlooking one of Europe's most dynamic cities.
Sir Norman Foster won the competition for the design of the 950ft (290m) tower in 1988. His clients were RTVE (Radiotelevision Espanola), Telefonica and CCRTV (Corporacio Catalana de Radio i Televisio). They wanted a platform for their latest broadcast, relay and signal-processing equipment - but they also wanted the structure to be a work of distinctive and memorable architecture, a symbol for the city (as the Eiffel Tower has been for Paris since 1889), and a building accessible to the public.
The result is a robotic structure of great power and presence. Its genius lies in the fact that, although its design is stripped to functional essentials, Foster and his engineers (Ove Arup & Partners in London with Julio Martinez Calzon of MC-2 and Ramon Pedrerol of CAST in Barcelona) have achieved a highly expressive structure.
The tower might have been a simple and dull concrete or steel mast laden down with electronic equipment. Instead, Foster has chosen a thin hollow concrete shaft topped with a needle-like radio transmitter. Like a ship's mast, the tower is braced by rigging made of pre-tensioned high- strength steel to stop it buckling or bending in the powerful Tramontana winds. Without these distinctive guys, the tower would need a shaft at least 90ft (27.5m) in diameter; instead, its maximum diameter is 15ft (4.5m) and at its peak the radio mast tapers to 2 1/2 ft (0.75m).
The bulk of the structure - 13 floors of electronic equipment with a public viewing gallery reached by a glass lift - is suspended from the central shaft by three steel trusses. If these 13 floors were used as offices, they could accommodate 900 people. Despite the lightness of its mast-like structure this is not a small building, yet it occupies very little ground space: its 10,700 ton bulk is carried on a concrete disc 75ft (23m) in diameter and 16ft (4.9m) deep.
Jean Nouvel's Tour Sans Fin will be even more spectacular than Sir Norman Foster's Torre de Collserola: a giant stack of offices, bars, restaurants and viewing galleries; the world's most slender skyscraper and, at 1,394ft (425m), one of the very tallest. Rising from a crater in the ground and disappearing into the sky, it expresses, according to Nouvel, the human obsession with infinity and an 'aesthetic of double disappearance'.
The tower is Nouvel's winning entry for a competition held in 1988 to develop the Triangle de la Folie, a tiny area of waste ground between the railway tracks at La Defense. The restricted site calls for innovative design and engineering solutions. Working with British engineers - Ove Arup again - Nouvel's circular tower will be 143ft (44m) wide, rising into the air without tapering or stepping back. Whereas American- style tower blocks have a central concrete core, the strength of Nouvel's building will lie, like the exoskeleton of an insect, entirely in its external skin. The result is a slim concrete and glass chimney, free of columns in the centre of its 72 office floors, and without the unsightly ground-level bulge of more traditional high-rise buildings. Giant concrete lattices will run up opposite sides of the tower, with windows three storeys high allowing daylight to flood into the core of
the building. The office accommodation is arranged in three stacks of
24 floors, with lobbies between the stacks.
For the top 200ft (60m), where concrete gives way to an exposed filigree steel structure, the tower narrows to a diameter of 40ft (12m). Here the public will be able to gaze at the vast pendulum and damping system that promises to alleviate the unnerving swaying and sea-sickness experienced by people in more venerable skyscrapers.
According to Tony Fitzpatrick, Ove Arup's chief engineer on the project, the decorative style of architecture with which Nouvel made his name (as in the popular Institut du Monde Arabe, Paris) has not been abandoned because of the strict engineering considerations involved in the construction of the tower, but for aesthetic reasons. 'It's all part of this wonderful French urbanism', he says. 'It's amazing for a client to sit and have discussions about a building's urban context, its effect at ground level and its effect as a work of art. You don't believe what people say about the sensibility of the French until you work with them.'
For Nouvel, sensibility dictates variations in the tower's skin as it shoots skywards: from mineral solidity in the crater to ethereal transparency where it disappears into the heavens. In the daytime, rough granite at ground level and polished aluminium at the top, perforated with a variety of clear and reflective types of glass - Nouvel's trademark, which was used to good effect in the Institut du Monde Arabe - will help the tower to blend into the sky. At night, coloured light will pour put through its 74 office floors and its filigree metal crown.
La Tour Sans Fin is not one of President Francois Mitterrand's grand projects; it is a strictly commercial venture, the estimated cost of pounds 600m being met by private backers, led by the Caisse des Depots et Consignations, the state-owned French investment bank. It augurs well for the future
of Paris that private money is prepared to take over where the president left off.
Nouvel sees the tower, on which construction is due to start next year, as a necessary symbol for the revitalisation of Paris as an international business centre. It will also be a healthy sign of the continuing sponsorship of daring modern architecture which has so characterised the city over the past decade - a sponsorship also enjoyed by Barcelona, but rarely, to date, by London, city of overweight architecture.
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