30 aug 11 | Arabian Business
Kingdom Tower architect grapples the wind at 3,000 ft
Kingdom Tower, Saudi Prince Alwaleed bin Talal’s project to erect the world’s tallest building in Jeddah, is designed to imitate the contours of a sprouting desert plant. Adrian Smith’s task is to make sure it doesn’t sway in the wind like one.
The American architect has the right resume for the job. He already grappled with effects like horizontal wind divergence and negative pressure high above the Gulf desert when he designed Dubai’s Burj Khalifa, today’s highest tower.
“Wind can move the tower from side to side and when the movement is rapid, people inside will feel it,” Chicago-based Smith, 67, said in a telephone interview. “We design to reduce that effect.”
Kingdom Tower will rise from three separate bases in continuous slopes that end at different heights, helping to balance the building’s weight and stabilize it against winds that can reach 120 miles per hour at the top. The 1,000m structure will cost $1.2bn to build over the next five years and will include a Four Seasons hotel, apartments, offices, three lobbies on the upper floors and the world’s highest observation deck on the 157th level.
Wind is the enemy of tall buildings, Smith said. The Burj Khalifa was designed as a collection of tubes reaching various heights around the central core to help “confuse” the wind by preventing it from forming whirlpools of air, he said.
“We learned from Burj Khalifa that the more steps you have, the better you shed the vortices, and that helps stabilize the building against any horizontal wind divergence,” Smith said. “Kingdom Tower will do that by having a continuous series of slopes to the top, which is more effective but more expensive.”
The tower is designed to move about 1 meter side-to-side at 500 meters in the most severe storms that occur once every 50 years or so, he said. The movement will be much less in more typical weather conditions.
Smith worked at Skidmore, Owings and Merrill when he designed the Burj Khalifa, which opened in January 2010. Now a partner at Adrian Smith + Gordon Gill Architecture in Chicago, the architect says his passion for reaching new heights hasn’t diminished.
“I’ve been drawing tall buildings since I was a child in California,” he said. “Each building that gets designed and built in the super-tall tower range adds about 10 percent to the whole base of knowledge for all architects out there,” he said. Kingdom Tower will be about 50 floors higher than Burj Khalifa and its design will constantly evolve, Smith said.
Filling a giant tower is another matter. Apartment owners in the Burj Khalifa were forced to slash rents by 40 percent after the building failed to attract tenants, Better Homes, a broker that marketed the properties, said in October.
“This is about making a statement and not addressing any real needs in the market,” said Majed Azzam, a real-estate analyst at AlembicHC Securities in Dubai. “However, there is a lot of concentrated wealth in Saudi Arabia and there will be enough take-up in such a large country.”
Apartment prices in Kingdom Tower will probably be comparable to luxury homes in Dubai and a two-bedroom apartment will probably sell for around SR3m ($800,000), which is very high for Saudi Arabia, Azzam said. Private developers prefer the upper end of the market, where profit margins are higher, than the needs of the wider population, which are hard to resolve without an active government role, he said.
The project’s owners haven’t provided any estimates of property prices in the tower.
Designing the world’s tallest buildings presents numerous challenges beyond high winds. The observation deck will stick out from the building in an 80ft-wide disc that was originally designed as a helicopter-landing platform, Smith said. The idea was abandoned after several pilots judged that landing there would be too risky.
Water must be pumped up the 163-floor Kingdom Tower in stages, using holding tanks at various levels, to avoid too much pressure building up in the pipes and causing them to burst, Smith said.
Evacuation also requires special planning. The Jeddah tower will have emergency refuge rooms every 20 floors, where people can stop to get water and protection while descending to the ground. Smith said he’s looking at ways to use the elevators in emergencies rather than following the common practice of banning their use.
“Any time you are fighting a fire in a tower, it’s localized to a particular floor or part of the building,” Smith said. “You don’t have to completely evacuate the building and the structure will be very robust here. It’s all concrete and the walls are 2ft thick for the most part, so fire won’t bring it down.
Smith’s design includes a system that collects moisture out of the air and from mechanical systems within the tower, producing enough fresh water each year to fill 14 Olympic-size pools. Summer temperatures in Jeddah, the gateway to Islam’s holiest sites in Mecca and Medina, can soar to 40C with 80 percent humidity.
The Kingdom Tower’s exterior walls will be made of glass with insulation behind it to help the structure control the heat, Smith said.
“We use glass because it’s easy to maintain and has longevity,” he said. “It also reflects the sky and helps the tower feel lighter and more elegant.”
Washing the tower’s windows will be a much simpler task than on the Burj Khalifa because it doesn’t have as much “complex exterior geometry,” Smith said. Still, it would take crews working around the clock for at least three months to clean the exterior because of the sheer size.
Residents and visitors will be carried by 59 elevators that travel 10 meters per second, including five double-deck elevators. For the first time, three-level elevators may be used to take visitors to the sky lobbies, observation deck and offices at the top of the tower.
The Burj Khalifa has the world’s highest swimming pool, on the 76th floor. Smith decided not to repeat the feat in Saudi Arabia, where at least two pools would be required because of the strict separation between the sexes.
Saudi Binladin Group, the country’s biggest construction firm, has been hired to build the tower as the centerpiece of a SR100bn development in Jeddah known as Kingdom City. The group will own 17 percent of Jeddah Economic Co, the project’s owner.
Bin Talal’s Kingdom Holding and Abrar International Holding Co each hold a third of the company and Abdurrahman Sharbatly owns the remaining 17 percent.
Binladin Group, which expanded the holy mosque in Mecca and built large projects across the Middle East, is owned by the family of deceased al-Qaeda leader Osama bin Laden.
Smith said he’s confident Kingdom Tower will attract tenants, citing market studies by the developer. While the building itself may not generate a lot of profit for its owners, it will raise the profile of the whole Kingdom City project, attracting buyers and boosting values, he said.
The design includes about 120 serviced apartments and 385 condominiums, although that number may change as the plan progresses. The building will include 54,000 sq m of office space distributed between the lower and upper floors.
Saudi buyers may use apartments in the tower as vacation homes to take advantage of Jeddah’s mild winter weather, Smith said. They also may rent properties out to visitors who come for the annual pilgrimage to Mecca and want to extend their stay in the kingdom, Smith said.
“Saudi Arabia is ambitious about opening up to private business in a much more business-friendly environment,” he said. “In order to do that, you need all types of housing.”
Smith prefers living closer to earth - choosing a house over a high-rise apartment block - though his office is 23 floors up in downtown Chicago’s Harris Bank building.