The Shanghai Tower soars above the rest of the high-rise riddled Pudong neighborhood of Shanghai. Completed in January of this year and officially opening to the public next month, it's the tallest building in China and the second tallest in the world (behind the Burj Khalifa in Dubai).
It's also a symbol of a new generation of skyscrapers, illustrated by its other distinguishing feature: a long, narrowing twist in its facade. The tower is one of a crop of new twisting high-rises popping up around the world, which are the subject of the latest report from the Chicago-based Council on Tall Buildings and Urban Habitat (CTBUH). The report examines this growing trend, which has seen 15 spiraling towers built in the last 11 years, with 13 more currently under construction.
What's driving their development? It's a complicated mix of increased computing power, trend cycles, and sustainability.
Take the Shanghai Tower, for instance. The twist in the building's facade reduced the wind load by 24%, which ended up saving developers $58 million in structural material. "Reducing the wind [load] on a building of that magnitude can save significantly in terms of material," says Shawn Ursini, a database editor at CTBUH's Skyscraper Center and an author of the study. He cautions that not all twisting towers are built with sustainability in mind—but, if done right, a spiraling design can save on materials and energy consumption.
Ursini also points to the novel aesthetics of a corkscrew building, amid a backdrop of standard, rectilinear towers, as one of the driving factors of its popularity. On a practical level, recent advancements in software and building technology have made it possible to actually build these designs in a timely and cost-efficient manner.
The predominant style of skyscraper that rose out of the mid-20th century was a boxy, steel and glass structure that could look the same no matter the city. With standardized components, architects would know roughly the time it would take to construct, the materials needed, and how to build a tower safely and quickly, so owners could start getting a return on their investment.
Ursini says that design software is finally changing that paradigm. The twisting tower—defined in the study as a building higher than 295 feet that rotates its floor plates as it gains height—throws a wrench (or maybe a screwdriver?) into the standardized plans of the midcentury. "When you introduce the twist, the parameters change," says Ursini. Engineers and architects have to factor in wind loads, as well as seismic and structural loading, because the floor plates are changing and shifting. The size and positioning of windows can change depending on where they are in the tower's twist. "It adds complexity to the project because [the windows] have to be manufactured and installed in a particular manner," says Ursini. Better building software and technology has made it possible to construct these incredibly complex skyscrapers quickly, safely, and relatively cheaply.
But with that many complicating design factors still to consider, why bother? Ursini says that as high-rise architecture booms throughout the world, architects, developers and cities want to make their buildings stand out. Santiago Calatrava's neo-futurist Twisting Torso, constructed in 2005 in Malmö, Sweden, was the first twisting tower. Trained as an engineer before he became one of the world's most renowned architects, Calatrava was experimenting with what was structurally possible, what would be dynamic, and what would be truly recognizable.
Since then, twisting towers have gotten taller and the twists more dramatic, as with the F&F Tower in Panama City, Panama, whose stacked and rotated rectilinear floor plates give the building a "helix-like" look. When the Jeddah, Saudi Arabia-based Diamond Tower is completed in 2019, it will be the first to twist a full 360 degrees along its height, according to the report.
The CTBUH lists all 28 of the twisting towers built or under construction, but Ursini says that there are still more that have just been proposed—meaning this is a trend that will be around for a while. Key to its staying power, he says, will be its emergence with another construction trend: green building. "If the twist reduces energy you consume in the building," by reducing solar heat gain with placement of the windows as it does in some buildings, for example, "that will be the primary thing," he says.
In other words, if these towers can provide benefits like that beyond pure aesthetics, skylines worldwide may only get more twisted.