27 Oct 22 | CNN.com

How to build supertall: Designers of the world's tallest towers share their secrets

By Tom Page

The world's tallest building casts a long shadow. For more than a decade now, the 828-meter (2,717 ft) high Burj Khalifa has reigned over Dubai's skyline and architecture's collective conscious. It didn't just break the record; 62% taller than its predecessor, Taipei 101, it obliterated it. Its legacy has been remarkable -- and remarkably useful to the man who designed it.

Adrian Smith conceived the Burj Khalifa as an architect at Skidmore, Owings and Merill (SOM), but by the time the tower opened in 2010 he had started a firm of his own, Adrian Smith + Gordon Gill Architecture, alongside Gill and Robert Forest. Known as AS+GG, the company specializes in designing supertall and megatall skyscrapers -- buildings at least 300 meters and 600 meters respectively.

Supertalls are still relatively rare, with just 173 completed worldwide, and megatalls exceedingly so, with only three currently standing, according to the Council on Tall Buildings and Urban Habitat (CTBUH). Many more have been aborted at various stages. For anyone working in this field, "you don't have many examples to look at," said Smith, in a joint video interview with Gill and Forest.

"The ultimate learning experience is when the building is complete," he explained. "Anything other than that is paperwork." Which is why skyscrapers like the Burj Khalifa remain so relevant.

"To go back and see something that was done 15 years ago, and how that's weathering, or how it's performing, and talking to people about their experience or how the building is functioning is invaluable," added Gill. "There's no substitute for that."

For the past 15 years, AS+GG has crafted a portfolio of skyscrapers spanning Asia, North America, Europe and the Middle East. These designs have now been compiled into a new book called "Supertall | Megatall: How High Can We Go?"

The hefty tome is intended as a practical guide for both students and practicing architects. It's full of technical drawings explaining the innovations underpinning skyscrapers like the recently completed Central Park Tower in New York (472 meters) and the upcoming Chengdu Greenland Tower (468m), in China, all the way to concepts stretching above one kilometer high. It's architecture on the bleeding edge, charting a path for where skyscrapers could go next.

"It's surprising how few people on the planet actually know how a supertall is going to work," said Smith, who describes the subject as "more or less unknown."
So why is the firm all too happy to share its secrets?

A great idea never goes to waste

AS+GG's most famous design is the Jeddah Tower (formerly known as the Kingdom Tower) in Saudi Arabia.

The Jeddah Tower's height is listed as 1,000+ meters when finished, which would make it the tallest building in the world. Once scheduled for completion in 2020, the building was 58 floors high as of 2020, per "Supertall | Megatall," and has faced delays.

Smith said constructors have "protected everything that they need to protect" and "the building is not deteriorating." In response to enquiries about its resumption, Gill said "Never say never."

The Jeddah Economic Company, responsible for the upcoming Jeddah Economic City, in which the tower lies, did not respond to a request for comment on the status of the building by the time of publication.
One of the longest entries in the book is dedicated to the innovations packed within the tower's design, from extensive wind testing with a 1:4,000 scale model, to strategies for mitigating solar radiation, to a condensate-recovery system with the ability to collect 14 Olympic-sized swimming pools of water from the building every year.

But "Supertall | Megatall" also points out that the Jeddah Tower's structural system built on and refined that of the Burj Khalifa, with a three-winged, Y-shaped design for maximum stability -- seen in earlier designs like WZMH Architects' CN Tower in Toronto. Smith also said that the Burj Khalifa and the Jeddah Tower were inspired by the sharp, fully glazed Friedrichstrasse Skyscraper, an unbuilt design from the 1920s by German American Ludwig Mies van der Rohe.

Mies' building is "a perfect example of (a design) that wasn't realized that still has value," said Gill. This perhaps explains why "Supertall | Megatall" also contains AS+GG skyscrapers that were never built.

Many of those are from Dubai (in fact, it has more entries than any other city in the book). As a growing city with ambition to burn, the emirate has been a petri dish for bold projects for the past two decades. Proposed AS+GG skyscrapers include the Meraas Tower (526m), Za'abeel Signature Tower I (598m) and 1 Dubai Atrium City (1,000m). It's a flight of fancy to imagine what the city skyline would look like with their addition, but, like der Rohe' Friedrichstrasse, their absence has not been a total loss.

"That's why we talked about those projects that haven't been realized in the present tense (in the book)," said Forest. "It's not a graveyard of disused ideas."

"Tons" of lessons from these buildings have already found application in other AS+GG designs, said Gill. For example, the design development of the one kilometer-high "vertical city" 1 Dubai prompted discussions about mechanical systems, structural efficiency, elevators, fire safety, air and lighting, among other subjects, said Gill, "that made its way into a bigger dialogue around height."

In the final pages of "Supertall | Megatall," we see the evolution of 1 Dubai's three slender, interconnected towers in a set of design prototypes for mile-high skyscrapers that utilize three separate towers linked with a central structure for stability.

"I don't think a great idea ever goes to waste," said Gill.

Designing for the invisible

For cities trying to raise their profile on the world stage, supertalls can help establish a reputation. "There's no hiding these buildings," said Forest. "Regardless of the owner, it becomes a symbol of its location."

What worked for Dubai became a blueprint for Jeddah. But height isn't everything, and not necessarily the firm's primary concern (the mandate to make the Burj Khalifa the world's tallest building came from client Emaar, Smith reminded).

For AS+GG, height becomes a starting point for a series of problems to be solved; a scale that both necessitates and incubates innovation. The book suggests supertall and megatall buildings can update ideas in energy efficiency, lower carbon footprints, and bridge the built environment and the natural world through biophilic design. "We have an economy of scale that we can introduce ideas that will stick sometimes," says Gill.

The Biophilic Tower, an unrealized design from 2012 intended for Suzhou, China contains many departures from convention, including a spiraling vertical forest rising 119 floors, and solar shades inspired by the structure of leaves and honeycomb. But innovation is often hidden from the public view, Gill suggested.

"Sometimes I think people look at buildings and they can't quite tell what they're looking at," he said. "That is because we're often designing for the invisible ... things that people never see and don't ever engage with. But they're in the science and the design. And that's what makes the buildings just simply better."

With "Supertall | Megatall," the invisible finds its way into the spotlight. "The educational component to this book shouldn't be ignored," said Smith, who, like his partners, is happy for AS+GG's designs to find a second life as an industry resource. "As professionals, we have a responsibility to share our knowledge," said Gill.

The secrets of supertall, it transpires, don't want to be kept a secret at all.