Part 1 -Symbols of the Modern World
Part 2 -57 Stories of Light
Part 3 -Pride of Nashville
Part 4 -A Labor of Indecision
Part 5 -World Title Champion
Part 6 -A Building that Breathes

The world's tallest building has been enshrouded in secrecy since the start of construction early in 2006, and the project architect, Skidmore Owings & Merrill LLP, isn't about to betray any confidences. Burj Dubai — Dubai Tower in Arabic — surpassed 2,000 feet in late fall last year, easily making it loftier than the former world's tallest building, the Taipei 101 at 1,671 feet, and also higher than the world's largest freestanding structure, the 1,822-foot CN Tower in Toronto.

The developer, Emaar Properties PSJC, won't reveal the ultimate height of Burj Dubai, fearing that other mega projects soon to get underway will attempt to outbuild Burj.

But the current evidence suggests that Burj will eventually get to 2,684 feet, with 160 habitable floors. The cost is pegged at $4.1 billion, making Burj the linchpin of the planned $20 billion Downtown Burj Dubai. This urban oasis also features the world's largest shopping center.

The principal designer of the Burj was Adrian Smith of SOM. He left the firm nearly two years ago to set up his own shop, Adrian Smith + Gordon Gill Architecture. Another SOM managing partner, George J. Efstathiou of the firm's Chicago office, has replaced him as the manager of Burj, overseeing a team of 90 architects and engineers at SOM plus another 50 consultants from the outside.

SOM is doing all the work, somehow, without a full-time office in Dubai, though Efstathiou and other principals travel back and forth constantly.

The building is conceived as a mix of retail, office, condominiums and a hotel, the latter the first Armani Hotel in the world. The scale is breathtaking.

Samsung Engineering & Construction used 110,000 metric tons of concrete for the concrete and steel foundation, which features 192 piles, each buried more than 150 feet deep. The 56 elevators, each with a capacity of 42 people, travel at top speeds of 40 miles per hour, making them the fastest ever built. There will be 3 million sq. ft. of space above ground, another 2 million sq. ft. below ground.

The design is an amalgam, with the bundled tube form borrowed from the Sears Tower and the triple-lobed footprint evoking the petals of a rare Middle Eastern flower, hymenocallis. There are numerous setbacks as the building rises, shrinking the cross-section of the floorplates, and near the top only the central core emerges, with plans for a spire.

A Y-shaped floor plan gives residents maximum views of the Persian Gulf. “In a residential floor plan you don't need depth in your floor plan. We developed a shape that would maximize the amount of glass area for each room,” says Efstathiou. “Light and air are what people really care about.”

The natural building material of choice in the arid Middle East is concrete, but to get it past 100 stories has been a huge challenge for Samsung. Special mixes prepared at the base of the building are strong enough to support the weight of Burj, yet also watery and light enough to be pumped to the top of the building.

An added challenge — concrete doesn't set well in 120-degree temperatures, so Samsung adds ice to its concrete mix and pours it at night when temperatures are cooler.

The numerous setbacks should limit sway at the top to one meter, Efstathiou says. “We've simulated the building many times in wind tunnels with sensors attached to our model,” he reports. “What's important in a high rise is that you don't want the human middle ear to sense motion, which can give people a feeling of seasickness. That won't be a problem here.”