Two New Tents
The city of Braga is noted for its religious festivals, and for being the ecclesiastical capital and seat of the country's archbishops. This temple to another kind of religion provides a focus for the new urban park planned around the slopes of Monte Castro and along the course of the River Cávado.
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The baroque theatricality of the stadium easily dominates its rugged mountain surroundings. Initially it was to be sited near the river, but was moved up the hillside due to the region's heavy rainfall.
The one million cubic meters (35 million cubic feet) of stone that was removed to form the huge, rock-lined amphitheater in which the stadium sits was later used in its new concrete superstructure.
Seating was removed from the goal-ends of the pitch and consolidated into two backward-canted stands, each seating 15,000 spectators in two overlapping tiers. The elimination of the cheaper seats behind the goals guaranteed optimal viewing for everyone.
The stadium pitch is oriented northeast to southwest, with the northeast stand dug into the hillside and rising against a backdrop of living rock that is approached from above via the main external plaza. This wall of rock is confronted by outward-leaning, heavy concrete piers and the undercroft of stairs, lifts, and concourses, while on the opposite side, the second stand leans out at an angle on broad concrete blades like the ribs of a ship.
Circular holes of varying diameters were punched into the concrete to reduce the overall mass, and staircases were inserted in between the structural blades.
The two stands are shaded by lightweight roofs of ribbed metal panels slung between parallel series of steel tensile cables. The roof edges are stabilized laterally by lightweight V-section trusses that run along the leading edge. The trusses double as supports for the lightweight gantry, thereby eliminating the necessity for intrusive floodlight towers.
Roof drainage is equally simple and direct. Freestanding, cantilevered concrete troughs collect the rainwater discharge at the roof edges and carry it down the hillside in open channels. This concrete rainwater structure is not only practical and easy to maintain, but is also an adjunct sculpture to the stadium, helping to lead the eye beyond the building into the landscape.
The Braga stadium is a monumental hyperbole: its supports are much larger and heavier than seems really necessary, and its roof is so light as to seem almost incomplete. Like David and Goliath, the stadium's two parts struggled against each other, each determined to win.
Burj Al Arab Hotel
At 321 meters (1,053 feet), the Burj Al Arab Hotel in Dubai, United Arab Emirates, is one of the tallest hotels in the world, exceeded only by the 333-meter- (1,093-foot-) high Rose Tower (completed in 2007), also in Dubai. The world's first "seven-star" hotel, it is also one of the most luxurious and spectacular in a region where luxury is a commonplace.
Designed by Atkins and built on a man-made island just off the coast, the tower can be seen from all sides. And much like the Sydney Opera House, it is an impressive sculptural object, surrounded by the waters of the Persian Gulf (known as the Arabian Gulf in the United Arab Emirates).
Its enormous fabric wall is a deliberate reference to the billowing sail of lateen-rigged Arab dhows, but instead of one there are two long, tapering yards, one for each side. And instead of the customary triangular lateen sail slung diagonally across the mast, these two curving arms rise vertically over the top and meet the mast behind the tower.
The hotel plan is an open V closed by an impressive translucent, double-layer membrane facade that creates a full-height atrium space, which, like everything to do with the hotel, was meant to set a record — in this case, the world's largest atrium. The twin 152-meter- (500-foot-) high towers at the west front of Cologne cathedral would easily fit inside it.
To achieve such exceptional height and lightness, a series of challenging structural conditions — related to wind conditions and the expansion and contraction of the membrane due to the wide variations in temperature — had to be met. The individual membrane panels are supported by 12 horizontal ribs, spaced at 14-meter (46-foot) centers vertically. The low weight per square meter resulted in savings in the weight of steel.
Some 7,500 square meters (80,700 square feet) of membrane and liner were required for the wall. Because the facade faces south, only two to three percent transparency was necessary to naturally illuminate the atrium.
PTFE (polytetrafluoroethylene) membranes are UV-resistant, noncombustible, and have a high reflectance. The smooth membrane surface self-cleans every time it rains, and normally does not require further cleaning. The life expectancy of the material is in excess of 30 years.
Lighting can be used at night to change the membrane color from white to yellow, green, violet, or red, or combinations of the above. The top and bottom can be different colors (red top, blue bottom), and there are many other possibilities, such as yellow-violet or red-green combinations, to enliven the night scene.
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Philip Drew, a distinguished architecture critic, is the author of monographs on Harry Seidler, Glenn Murcutt, and Arata Isozaki, and is a regular contributor to international architecture and design magazines. He lives in Sydney, Australia.
This article is excerpted from New Tent Architecture by Philip Drew, copyright © 2008, with permission of the publisher, Thames & Hudson.