NYguy |
Jan 2, 2015 7:40 PM |
Quote:
Originally Posted by toxteth o'grady
(Post 6860399)
The fact that a building can go 1500 feet in the air and have only 230 units suggests the supply will be hard-pressed to meet the demand. Though why this wouldn't be happening in Houston and San Francisco is a bit of a mystery.
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Not a mystery.
http://www.citylab.com/design/2014/0...ywhere/373493/
Why Can't We Build Skinny Skyscrapers Everywhere?
The limits to how tall and thin towers can be has more to do with markets than engineers.
KRISTON CAPPS
Jun 26, 2014
Quote:
.....In Manhattan, architects are building highest and fastest in Midtown. There, the supertalls aren't just tall—some of them are superskinny, too. A group of buildings along West 57th Street with residential units priced from $5 million to more than $100 million has transformed the Central Park perch into Billionaires Row, a signifier of America's new Gilded Age. In most cases, each unit is basically its own penthouse suite, occupying an entire floor of its building.
Taken on their own terms, the superskinnies represent a feat of architectural design. The new developments going up on West 57th Street may, in fact, be approaching the outer limits of the tall-to-thin aspect ratio for a structure. Just not for the reasons you might think.
"Structurally, there are a lot of very unique challenges, especially for a building that wants a high degree of special views," says Vishaan Chakrabarti, a partner at SHoP Architects and the director of the Center for Urban Real Estate at Columbia University. SHoP—the firm that designed the Barclays Center as well the forthcoming Domino Sugar Refinery development, both in Brooklyn— is responsible for what may be New York's, and the world's, skinniest supertall.
I use that term advisedly: "Supertall" is a category of building defined by the Council on Tall Buildings and Urban Habitat as between 984 feet and 1,968 feet in height. (Anything much taller than that is, technically speaking, "megatall," and not permitted in the U.S. by the Federal Aviation Administration.) The SHoP Architects project in Midtown—111 West 57th St.—is not only a giant at 1,350 feet. It's also strikingly narrow.
"The majority of the shear load is happening on the east and west façades," Chakrabarti explains, referring to one of the fundamental forces that architects and engineers have to account for in designing buildings. Those façades will boast another bravura element of the design: a system of terra-cotta blocks.
"[The design] gives the building a sense of stability," Chakrabarti says. "It’s a slender building, but a stable building. The main structural challenge is taking the core and using the east and west shear walls to stabilize the building."
Down the road is 217 West 57th St., another supertall, superskinny Midtown tower. This isn't, strictly speaking, the project with the sharpest aspect ratio that architect Gordon Gill has ever designed. That honor belongs to the trident-shaped tower designed by architecture firm Adrian Smith + Gordon Gill for One Dubai in the United Arab Emirates, a $95 billion—billion—mega-development planned by firm Skidmore, Owings & Merrill (SOM). But 217 W. 57th St. will nevertheless be one of the skinniest towers in Manhattan and the nation.
"The complexity just increases when you get slender," Gill says. "The floorplates become smaller, but the views can become really amazing."
This new kind of skyscraper is popping up all over Midtown—but so far, only there. There are reasons that superskinnies haven't shown up in Chicago, Los Angeles, San Francisco, Dallas, or other cities. Nor are they likely to get much skinnier in Manhattan.
"From an engineering standpoint, there’s a ways to go," Gill says when I ask him how tall and thin the firm can build. "From an economic standpoint, we’re close to the limit."
"We cut slots, we punch holes, we create notches in the corners of the buildings" to mitigate the effects of wind, Gill says, on tall and thin buildings alike. But there are some places where superskinnies will just never go. No matter how pitched income inequality comes to be in San Francisco, these towers will never rise there. "For areas that are seismic, the slenderer buildings are not advisable," Gill says.
"It stops making sense in terms of elevatoring," Chakrabarti says. Vertical circulation—elevator shafts and related mechanicals—don't get skinnier as a tower does. For a project like 111 West 57th St., where each floor constitutes a single huge apartment, this means that elevators chew up floorplate as you rise. And since the entire tower yields only about 300,000 square feet of residential space, there isn't a lot of square footage to lose.
You could go taller with these skinny towers, but it would require something that no U.S. city has in spades: abundant land downtown available for development. The higher you go, Gill says, "the land area you require increases. Doubles. Triples." At a kilometer high, Kingdom Tower's footprint is still manageable. But at a mile high, the base that a building requires becomes much, much larger.
"You end up carving that stuff up [the base area]," he says. "There’s an economics to it that suggests that at this time, and this place, this is what we can do."
.....In other words, these superskinnies are unique—a "registration of the market," as Chakrabarti calls them. "It is a typology that’s happening, no question," he says, noting that SHoP has at least two more supertalls coming to New York. "But if I look at our overall portfolio, [superskinny, supertall] is not an enormous percentage in terms of square footage."
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