By Anthony Paletta
April 6, 2022 6:10 pm ET
. . . Mr. Al, a Dutch architect based in New York, writes that “we are living in an urban age where the most tangible architectural expression . . . is the supertall.” In 1996, he notes, the Council on Tall Buildings and Urban Habitat only classed four buildings as “supertall”: 984 feet or taller. “Today, there are more than one hundred seventy, with about a dozen completed every year—each taller than the Empire State Building.”
. . . Mr. Al’s account spans the behemoths of Asia and the Middle East, the pencil-thin towers of Manhattan, the eccentric geometries of high-rise London, the vertical gardens of Singapore, and more.
The sheer volume of calculation required to build and keep these structures aloft and functioning is astounding. Mr. Al, who has written an excellent book on the architecture of the Las Vegas Strip, explains these esoteric technical challenges in lucid fashion. If steel was the literal foundation for the first century of skyscrapers, reinforced concrete is that of the second. The latest “ultra-high-performance” concrete, Mr. Al explains, supports “about 26,000 pounds of pressure per square inch—the weight of three African elephants on an area the size of a postage stamp.”
As Mr. Al informs us,
the precise ingredients of concrete, and the ways in which you combine them, are vitally important. Local sand was too round and small for the Burj Khalifa in Dubai, so Australian sand was shipped in. One key innovation in recent decades is the use of “superplasticizers,” synthetic polymers that render concrete stronger and workable for longer.
Supertalls don’t merely have to support their own weight; they have to resist wind pressure. The darkest prospect is vortex shedding, in which a strong wind causes air to separate from the building’s surface, “creating two symmetrical and adjacent low-pressure eddies on the downwind side,” as Mr. Al writes. As wind speed increases, the vortexes begin to alternate from side to side, which could lead to disaster if the movement coincides with the building’s natural vibration. “In this case,” Mr. Al writes, “even small amounts of wind can lead to major oscillations, and could lead to collapse.” He likens the phenomenon to an opera singer shattering a wine glass.
Wind pressure has spurred developers to devise irregular shapes, relieving the monotony of the rectangle. The Canton Tower in Guangzhou, China, for example, is something of a cylinder cinched in the middle, while the Turning Torso in Malmö, Sweden, twists upward. Tuned mass dampers, large devices that move in the reverse of the tower’s motion, are standard in these sorts of buildings.
Getting to the top is a challenge; walking 3,000 stairs is not an option. Contemporary supertalls rely on innovations like high-speed “express” elevators and double-decker cars. The Empire State Building’s elevator initially traveled 14 miles per hour; current elevator speed is up to 47.
Elevators today are safer than ever: The Shanghai Tower features safety gears that “can withstand friction heat as high as 1,000 degrees Celsius” and a telescopic buffer at the base of the shaft that serves as a life net.
Another problem (and massive environmental hazard) is the tremendous amount of climate control required in supertalls, where operable windows are generally unthinkable. The Burj Khalifa, for instance, has seven double-level mechanical floors to move water and supply air-conditioning. Desert supertalls may seem the diametric foe of energy efficiency, but Mr. Al surveys some recent experiments to find ways of mitigating this waste.
According to Mr. Al, New York is the city of the “super slenders,” which are largely residential, as opposed to the commercial skyscrapers of the previous century. Some of these “Billionaires’ Row” sylphs are ugly, but he puts in a welcome good word for the concept. “Super slenders balance the skyline,” he writes. “Aesthetically speaking, their thin peaks add big crescendos, allowing for diminuendos elsewhere, avoiding the otherwise monotonous solid wall of equally high-pitched buildings.”
Hong Kong features a far denser skyline but has done a better job of integrating the buildings into the city, with plentiful direct connections to transit and frequent links between buildings above the first floor. In Singapore there have been welcome efforts to achieve more sustainable buildings and to bedeck them with greenery. The architect Moshe Safdie topped his Marina Bay Sands with a “SkyPark.” The city’s Tree House, at 24 stories, may not be supertall, but one of its sides is covered by a vertical garden.
Mr. Al’s account isn’t simple boosterism, but it does dodge the tone of miserablism that characterizes so much attention to our skylines. Supertalls are fascinating and immensely complicated undertakings that demand admiration—and lots of work. Even if tweaks are necessary, the story of what’s come about in the age of the supertall is gripping. “If we can harness our ingenuity to build structures up in the clouds,” Mr. Al wisely counsels, “then we can also create structures that are good for the planet down on earth.”
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https://www.wsj.com/articles/superta...ts_pos3&page=1
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