How High Will They Build?

World-beating skyscraper engineering isn't dead. Across the Pacific, new technology is feverishly being deployed to set records.

by Skidmore, Owings & Merrill, LLP

Jin Mao Tower Shanghai, China, completed in 1999
China’s tallest building, shown here under construction in the summer of 1996, will soon be dwarfed by a tower in Taiwan.

IN SEPTEMBER 2001, New York developer Donald Trump was dreaming of building the world’s tallest skyscraper, a 2,000-foot mega-tower that would return the record to America from Malaysia, where it had been lost, though not without controversy, to the twin Petronas Towers. Trump’s people met in Chicago with architects from the legendary firm Skidmore, Owings and Merrill, which had designed the magnificent John Hancock Center in that city, with its bridge-like exoskeletal steel ribs, and the Sears Tower, which had been dethroned by Petronas in 1996. What Trump and his collaborators imagined would have dwarfed them all: 200 stories, a stab at the heavens.

Then, news. During the Chicago meeting someone switched on a television. A plane had crashed into the World Trade Center in New York. “We watched as another plane hit, and then had to evacuate our building,” recalls architect Adrian Smith. “Later, Trump’s people called and said they didn’t want to build the tallest building anymore. They didn’t want to be a target.”

September 11 marked the end of an architectural era, if you believed the gloomy speculation. “Skyscrapers took a hit everywhere,” sighs Eugene Kohn, president of Kohn Pedersen Fox Associates (KPF), one of the world’s largest architectural firms. Critics of the WTC pointed out that buildings taller than 80 stories aren’t economically justifiable anyway. And how could the safety of occupants be guaranteed against devastating attack? As structural engineer Ron Klemencic notes: “It may be generations before America returns to skyscrapers.”

Not so fast.

Already there is talk of America reclaiming the crown, with several of the recent proposals for the World Trade Center site in Manhattan involving world-beating towers and structures. True, local economics, site-use concerns and, no doubt, fear mean those towers are unlikely to be built as high as proposed. But America isn’t where the race has been happening anyway. Petronas wasn’t an aberration; it signaled a new boom. If the 1930s were marked by the superb Chrysler Building and Empire State Building, and the 1970s by the businesslike Sears and WTC, then this 10 or 15 years — mid ’90s to, say, 2010 — marks the era of the Far East. Seven of the world’s 10 tallest buildings were completed in the late ’90s; eight of the top 10 are in Asia; Kuala Lumpur will pass the crown to Taipei later this year, and Taipei, likely, to Shanghai later this decade. Hong Kong, Seoul and Tokyo are also in the race. There’s no sign that terrorism, even post-Bali, will slow this down; some designers claim Asian towers are safer than the WTC was anyway.

Why the race? To be blunt, in Asia today, as in New York 70 years ago, nothing is more demonstrative than a huge, well, upright symbol. Rival nations and corporations work overtime to show they are high-tech powerhouses. “Height, as a manifestation of technology, is tied up with cultural aspirations,” says Eric Howeler, an architect with KPF, which is designing Union Square, a 108-story building that will, Howeler says, be the world’s tallest when completed in 2007. “This is true for relatively low-tech items like base building structure — steel or concrete — all the way to high-tech items like lifting, damping, signage, lighting.” Thus architects perch an 800-ton damping ball near the top of a 101-story building to counter sway caused by winds
in a typhoon region. Pressurized and double-decker elevators tackle the problem of speedily moving many people. Cold cathode fixtures and fiber-optic strands are incorporated into curtain walls to turn buildings into billboards for technology. And much is done with materials and building strategies to speed the construction process along.

THE CESAR PELLI-DESIGNED PETRONAS TOWERS confirmed how important the engineering and building of tall buildings is to Asian aspirations. Pelli’s pair of concrete rocket-shaped buildings in Kuala Lumpur are connected by an unusual sky-bridge and were a magnificent reply to the peninsular dominance of Singapore. “Those buildings put Malaysia on the map,” notes Kohn. The impact was enormous: The towers became instant icons in a city that not long before had been distinguished by low buildings from the Colonial era. All the better when the Council on Tall Buildings and Urban Habitat (CTBUH), the acknowledged arbitrator of height claims, decreed that, at 1,483 feet, the Petronas Towers beat the Sears Tower (1,450 feet) for the title of world’s tallest. It was a controversial decision, because if you look at scale drawings it’s clear that top-floor occupants of the Sears work at a considerably higher elevation than those in Petronas. “The question has always been, what constitutes a tall building,” says Klemencic, chair of the council, which decided that height would be measured from the ground to the architectural top of a building. Masts and antennas are disregarded, but pointy caps like those atop the Petronas are OK. “We felt, if the feature is an integral part of the design, it should be included,” says Klemencic. “Look at the Chrysler Building. Take away the crown and it’s no longer the Chrysler.”

China-Taiwan enmity dwarfs that of Malaysia and Singapore, so it’s hard to believe the nearly completed Taipei 101 will hold on to the crown for long. Shanghai already boasts the sleek 1,380-foot-tall Jin Mao Tower, the world’s fourth-largest building (counting the Petronas Towers as one and two) and the tallest in China. Even bigger will be the KPF-designed Shanghai World Financial Center next door. Only the foundation piles are in; construction stalled after the Asian financial crisis in 1997. Kohn says the project has restarted, with a redesign that will top Taipei 101. By how much? “That’s secret,” Kohn says, “but I guarantee it will be the tallest.” It will have strong competition: In January, a group of multinational companies announced their plan to add a 1,772-foot tower, by 2007, to a project already under way in Seoul.

Which raises the question, how tall can buildings go? Answer: No structural limit is in sight. Modern buildings are basically thin curtains draped on skeletons of high-stress steel or concrete materials. Columns shift weight to underground substructures in what are, despite their massive appearance, relatively low-density structures. According to Craig Gibbons, director of the Hong Kong office of Arup, a global structural engineering firm, “we could build a kilometer-tall building right now, no question about it. Two hundred, even 300 stories tall, is possible because we can take advantage of lighter, high-stress materials.” Wind load challenges require technology, but “making a building stand up, whatever the height, is relatively straightforward.”

One challenge not yet solved is getting bigger, heavier construction materials to the height required for a supertall building. Current crane and construction-elevator technology, Gibbons says, is not up to the job. “We’re talking columns that would be 4 by 4 meters in girth, like the size of a small room. And many stories in length. As you look at lifting those big pieces, then fitting them together, we’d need an advance in lift technology and in cranes.”

Klemencic echoes the common wisdom about supertall towers: “The limitations are more financial and practical, how to move people up and down those great heights. Above 80 stories, the area you need to devote to vertical lift, like elevators, versus rentable space, just is not viable.”

But it’s not a fixed equation. Advances in materials and elevators make tall buildings more efficient. Shanghai’s Jin Mao, topped by the world’s highest hotel, uses high-speed elevators that race along at about 30 feet per second; faster elevators reduce the need for more elevator shafts. Double-decker elevators can be employed, stacked on the same shaft, with improvement in floor space efficiency. Meanwhile, materials have grown stronger and lighter.

Faster-setting concrete mixes have erased the advantages of steel (a steel skeleton intrudes less into floor space than bulky concrete, and steel buildings can be erected more quickly, though they have to be fireproofed). Composite approaches, such as steel skeletons wrapped in concrete, are efficient, strong and fire-resistant.

If there is no structural limit, is there a safety limit? Typhoons, earthquakes, terrorist attacks — and fires caused by any of those — are real risks in Asia.

Mitigation of movement is a basic challenge in all tall-building design. Early high-rises were made stiff to resist wind, but the approach shifted long ago to buildings with give, incorporating tuned active and pendulum dampers that help absorb and counteract wind or seismic forces. The John Hancock Tower in Boston uses a big block of concrete floating in a bed of oil; computer-controlled hydraulics push it around to counter the building’s sway. Sydney’s Chifley Tower employs a pendulum, “a giant block of concrete hanging by wires,” Klemencic says. “It’s quite dramatic.” Taipei 101 will feature the world’s largest passive tuned mass damper, an 800-ton sphere 18 feet across that will swing like a pendulum from the 92nd floor in the view of restaurant-goers.

Fire may be a thornier problem than jolt and sway: It was fire that brought down the WTC, not the impact of the jetliners. Here KPF architect Eric Howeler argues that some Asian countries may lead the West in building codes and technological strategies. Basic construction is very different from that employed for the WTC in the 1960s. The New York towers were steel cages, with floors suspended from beams, and a post-collapse enquiry suggested that when fireproofing material on the steel blew off on impact, exposing beams directly to melting heat, it might have sped the collapse. A steel-concrete composite tower might be inherently safer.

Every 25 floors, Hong Kong buildings must have a refuge floor — empty and designed to resist smoke accumulation. Many stairwells are pressurized.

Atrium size is restricted. Water tanks on the roofs of tall buildings are sometimes engineered to let the water slosh about, doing double duty as wind dampers. Dedicated firemen’s lifts are required in many Asian cities. “In Hong Kong they are required to reach any floor in the building in an extremely short period of time, so they are profiled like a bullet to avoid drag, and travel as fast as 9 meters per second,” says Howeler.

“All this,” he adds, “existed before 9/11. After 9/11, a lot of studies were carried out to determine if changes were necessary.” Few were identified, but engineering responses to fire evolve. KPF decided to add a fifth stairwell to its planned Union Square because of evacuation concerns raised by harrowing stories from the WTC on September 11. At first the firm considered simply widening the stairwells, but realized that “a wider stair helps only if it is significantly wider, say, wider by an increment of a whole shoulder’s width.” Better five narrow stairwells than four that have been widened insufficiently for a crush.

Since September 11, Cesar Pelli has been constantly queried about the safety of the Petronas Towers and is outspoken in his belief that the concrete structures could withstand the impact of a jumbo jet. He points to the elevated bridge that connects the two buildings as an additional advantage: “That bridge could allow people to get from one tower to another in the case of such a catastrophe.”
Howeler agrees that Asian tower construction is safer than that of the 30-year-old WTC, but warns that terrorism by its nature is hard to plan for. “The forms that terrorism takes seem to evolve and mutate faster than the architectural means to guard against them.”

THE IDEA OF SUPERTALL TOWERS, vastly higher than anything now built, has long fascinated architects and urban planners. In 1956, Frank Lloyd Wright — who had decried skyscrapers in the ’30s and predicted the flight of people away from vertical cities — designed the Illinois Tower, a mile high, 528 stories in all, to be occupied by 100,000 people.

It was technically feasible, he said, but for the elevator problem. More recently, Tokyo mulled plans for Sky City 1,000 (3,281 feet, or 1,000 meters) and something called Mother (4,333 feet). Sir Norman Foster has sketched a pair of Millennium Towers: the 2,755-foot Tokyo version and another at 2,952 feet in Shanghai. (Foster’s proposal for a tower at New York’s WTC site would be, he said, “the tallest, the strongest, the greenest and the safest” ever built.) A pair of Bionic Towers proposed for Shanghai and Hong Kong by the firm Cervera & Pioz and Partners are each envisioned as a central 300-story skyscraper surrounded by a cluster of smaller buildings, a self-contained city with shops, apartments, cinemas and workspace for 100,000 people. This is offered as a response to the “superpopulation” problems of the future. The cost would be stratospheric — more than $14 billion, according to Chinese media. Pure fantasy? “We are considering it,” a Shanghai official told me during a recent visit to his planning office.

“But who wants to live in a building 1 mile high?” asks Mir M. Ali, an architecture professor at the University of Illinois and author of Art of the Skyscraper. He points to the claustrophobic social conditions of such a skyscraper, plus the diminishing pleasure of views when you are literally in the clouds. A more realistic height for the 21st century, he believes, is around 150 stories and 2,000 feet.

Architects like Pelli have already designed such towers. Likewise SOM’s Smith and KPF’s Kohn. All three were for Chicago. “Humanity has an obsession with building big,” says Pelli, whose Two International Finance Center will soon become Hong Kong’s tallest tower. “Part of it is the human element. That’s why a tall TV tower isn’t so important. When we see humans in a building, and know there are eyes up there, that’s the emotional connection. Tall has power.”

**Ron Gluckman, who writes for Time, Newsweek and Travel & Leisure, has been based in Asia for 13 years. He loves tall buildings but is scared of heights.
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