Awash in the harsh sun of the Saudi Arabian desert, the gleaming 984-ft.-tall Kingdom Centre shimmers like a mirage as it towers over the Riyadh skyline. Rising from an elliptical base, the almond-shaped tower is topped by a dramatic yet simple inverted catenary arch, adding an element of geometric mystery to its dominating presence.
The newly completed 3.3 million-sq.-ft. mixed-used facility is the dream of Prince Alwaleed Bin Talal Bin Abdulaziz Alsaud, nephew of King Fahd, grandson of King Abdulaziz, founder of Saudi Arabia, and owner of the Kingdom Holding Co. The fruit of the prince's desire to build an iconic structure on a par with the Eiffel Tower, the center is the same height as the Paris landmark.
Though his requirements were straightforward — to build a simple, strong, monolithic, and symmetrical structure — the prince rejected more than 100 designs from firms around the world before turning to Minneapolis-based A/E Ellerbe Becket. The firm teamed with Omrania & Associates, an A/E firm owned by the prince, to form Ellerbe Becket/Omrania Consortium.
"The prince said he wanted a design that he could sketch on a napkin," says Philip Oliver, one of Ellerbe's project designers for the center. The firm produced a dozen different designs for the prince, including the silver reflective-glass curtain-wall structure. "When he saw the model for this project, he hugged it and said, 'This is my building,'" says Oliver.
With more than 3 million people, Riyadh, like most Arabian cities, is spread out. The city's zoning ordinance, which limits the number of floors in a building to 30 but permits building heights of up to 300 meters, resulted in a unique design for the skyscraper. The lower two-thirds of the building are comprised of reinforced concrete up to the 30th floor. The top third of the building constitutes a decorative sculpture made of a structural steel skeleton. A shallow-arch observation bridge spans 60 meters across the top of the parabolic curve.
"The entire top of the building is essentially a sculptural form filling out the building up to the observation deck," says Oliver.
Steel hat alters structural properties
"It's rather unique," says Leo Argiris, a principal with the New York office of Arup, the project's structural engineer. "It's a thousand-foot-tall, 30-story building with a 100-meter hat."
Because its mass is lower than typical buildings of this height, the building does not follow standard engineering rules, says Argiris. "The lower mass affects the building's dynamic properties," he says. With the top third of the building unoccupied, the drift criterion for the building was slightly relaxed, says Argiris. "Serviceability is more defined for the top occupied floor," he says. Because the observation deck is closed in high-wind conditions, the drift criterion does not impact it as significantly as it otherwise might.
A unique aspect of the construction sequence involved the observation bridge, according to Ellerbe's Oliver. It was constructed atop the concrete structure on the 30th floor and then jacked up as the structural steel grillage was assembled for the sculptural headpiece.
Mixed-use components
Located on 23 acres, the property offers a mixture of uses. The tower contains a breathtaking 72-ft. lobby and 14 office floors, including the headquarters of one of the country's largest banks. A 10-floor, 225-room Four Seasons hotel, said to be the first five-star hotel in Saudi Arabia, followed by four floors of apartments and one condominium floor, tops this. Kingdom Holding Co. occupies the 30th floor.
A three-story retail mall is located in a podium to the east of the tower's base, housing two anchor tenants. The west podium contains a sports club, complete with tennis courts and pool, as well as a wedding and conference center. Weddings are big events in Saudi Arabia, says Oliver, and can routinely involve a thousand people or more. Two levels of parking located beneath the retail and conference podiums provide 3,000 parking spaces.
Islamic design elements were incorporated into the project to accommodate Saudi religious and cultural traditions. The third floor of the retail mall is for use by women only, enabling them to shop without having to wear traditional coverings. Glass screens along the atrium edges of the floor obscure views into the area. Separate elevators and a drop-off area also are provided. Prayer rooms are located throughout the project.
The tower shape, being wider in the middle, enabled the design team to locate separate elevators for each of its mixed-use components in the building's core. Visitors to the observation deck transfer to a perimeter elevator just above the 30th floor for the remainder of the ride. Mitsubishi Electric Saudi Ltd. supplied the elevators.
To reduce solar heat gain in a climate that can hit 130 F in summer, designers sited the project so that the slim ends of the tower face east and west, preventing sunlight from directly striking its wider 252-ft. north and south faces. Sheathing the tower in reflective glass curtain wall and providing liberal use of sun-shading devices on the podiums also were intended to reduce heat gain and increase energy efficiency. Sunshades adorn all of the carports. Large porte-cocheres at the north and south entrances of the tower provide shade and protection from desert rainstorms. Large canopies on the mall side shield the lower two levels and the women's level from the sun, as does a brow that runs the length of the vehicular drop-off on the west podium.
The curtain wall was selected because of the monolithic appearance it gave the tower. "The intent was to create a singular form. That's why it's a pretty tight curtain wall," says Oliver.
Arup's London office was the project's façade engineer. "Façades are becoming more complex elements," says Argiris. "The goal was for the façade to have a tight skin and for the tower to look like an extruded object. We defined the procurement and worked with the wall supplier to ensure the performance and the architectural intent was carried through."
Although the mall and conference center have been open for months, the official grand opening of the project has been held up by the war in neighboring Iraq. Nonetheless, says Ellerbe's Oliver, this minor setback has not dulled the impact the gleaming skyscraper has made on the landscape of the city, nor has it clouded the prince's vision of a Saudi Arabian icon.
