Burj Dubai stretches almost a kilometre skyward. Photo from www.burjdubai.com
The world’s tallest tower opened on January 4 in Dubai, with fireworks and an official announcement that it was 828 metres high. The Burj Dubai was also renamed Burj Khalifa.
The surprise renaming is in honour of Sheik Khalifa bin Zayed Al Nahyan, the ruler of neighbouring Abu Dhabi and president of the United Arab Emirates. Sheik Khalifa has poured millions of rescue dollars into Dubai since the formerly booming resort’s economy and real estate market collapsed last year.
The Dubai skyscraper is easily the tallest building in the world, standing 305 metres high than its nearest rival, the Tapei 101 in Taiwan, which has been the world’s tallest building since 2004. Toronto’s CN Tower is 553 metres.
Skidmore Owings Merrill of Chicago (with SOM’s William Baker as structural engineer) designed the tapering tower, which is visible 95 kilometres away. Ontario’s RWDI performed wind analysis (see CCE, December 2008, page 34-35). Emaar Properties is the developer.
Costing $1.5 billion, the tower has 165 habitable floors. It will boast the world’s highest mosque on its 158th floor, and a swimming pool on the 76th floor. There’s also an observation deck at the 125th floor which costs around $27 to access.
Following is a description of the tower’s structural design from the Burj Dubai website. For more details about the foundation, podium, cladding, spire, mechanical systems, fire protection, etc. see www.burjdubai.com/the-tower/structure.aspx
“In addition to its aesthetic and functional advantages, the spiraling “Y” shaped plan was utilized to shape the structural core of Burj Dubai. This design helps to reduce the wind forces on the tower, as well as to keep the structure simple and foster constructability. The structural system can be described as a “buttressed core”, and consists of high performance concrete wall construction. Each of the wings buttress the others via a six-sided central core, or hexagonal hub. This central core provides the torsional resistance of the structure, similar to a closed pipe or axle. Corridor walls extend from the central core to near the end of each wing, terminating in thickened hammer head walls. These corridor walls and hammerhead walls behave similar to the webs and flanges of a beam to resist the wind shears and moments. Perimeter columns and flat plate floor construction complete the system. At mechanical floors, outrigger walls are provided to link the perimeter columns to the interior wall system, allowing the perimeter columns to participate in the lateral load resistance of the structure; hence, all of the vertical concrete is utilized to support both gravity and lateral loads. The result is a tower that is extremely stiff laterally and torsionally. It is also a very efficient structure in that the gravity load resisting system has been utilized so as to maximize its use in resisting lateral loads.
“As the building spirals in height, the wings set back to provide many different floor plates. The setbacks are organized with the tower’s grid, such that the building stepping is accomplished by aligning columns above with walls below to provide a smooth load path. As such, the tower does not contain any structural transfers. These setbacks also have the advantage of providing a different width to the tower for each differing floor plate. This stepping and shaping of the tower has the effect of “confusing the wind”: wind vortices never get organized over the height of the building because at each new tier the wind encounters a different building shape.” — Source: http://www.burjdubai.com/the-tower/structure.aspx