The design concept of the world tallest building

"Structural Design of the World’s Tallest Building:
The Burj Dubai Tower"

By:
William F. Baker, SOM Partner in Charge of Structural and Civil Engineering , Chicago, IL
D. Stanton Korista, SOM Director of Structural Engineering, Chicago, IL
Lawrence C. Novak, SOM Associate Partner,
Chicago, IL

The Burj Dubai Tower, when completed, will be the world’s tallest structure. The superstructure is currently under construction and as of the start of 2007 has reached near 100 stories. The final height of the building is a “well-guarded secret.” The height of the multi-use skyscraper will “comfortably” exceed the current record holder of 509 meter (1,671 ft) tall Taipei 101. The 280,000 m2 reinforced concrete multi-use Tower is utilized for Retail, a Giorgio Armani Hotel, Residential, and Office. The goal of the Burj Dubai Tower is not simply to be the world’s highest building; it’s to embody the world’s highest aspirations.

Designers purposely shaped the structural concrete Burj Dubai—“Y” shape in plan—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 a “buttressed” core. Each wing, with its own high performance concrete core and perimeter columns, buttresses the others via a six-sided central core, or hexagonal hub. The result is a tower that is extremely stiff torsionally. SOM applied a rigorous geometry to the tower that aligned all the common central core and column elements to form a building.

Each tier of the building steps back in a spiral stepping pattern up the building. 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. This allows the construction to proceed without the normal delays associated with column transfers.

The setbacks are organized such that the Tower’s width to change at each setback. The advantage of the stepping and shaping is to “confuse the wind.” The wind vortexes never get organized because at each new tier the wind encounters a different building shape.

The 280,000 m2 (3,000,000 ft2) Tower and 185,000 m2 (2,000,000 ft2) Podium structures are currently under construction and the project is scheduled for topping out in 2008.

The design for the 270,000 square meter Burj Khalifa (formerly Burj Dubai) combines historical and cultural influences with cutting edge technology to achieve a high-performance building. Some of these technologies are:

• High performance glazing with Low E coating: A low-emissivity glass provides Burj Khalifa with enhanced thermal insulation against high ambient temperatures of Dubai.
  
• Sky sourced ventilation: Cooler air temperatures, reduced air density, and reduced relative humidity at the top of the building allow for “sky-sourced” sustainability innovations. When ventilation air is withdrawn at the top of the building, it requires less energy for air conditioning, ventilation, and dehumidification.
  
• Condensate recovery system: Burj Khalifa has one of the largest condensate recovery systems in the world. Diverting and reusing water from air conditioning condensate discharge prevents it from entering the wastewater stream and reduces the need for municipal potable water. Estimated annual savings are equal in volume to 14 Olympic sized swimming pools.
  
• Higher voltage power up in building: Conduction of electric power using higher voltage reduces energy losses and increases energy efficiency when compared to low voltage energy distribution.
  
• Electronic metering: Individual electric energy monitoring systems enable ongoing energy optimization of the tower’s systems over its lifetime. This will result in a reduction of Burj Khalifa's energy related environmental impact.
  
• Smart lighting and mechanical control: Burj Khalifa's building management system (BMS) provides the tower with low operational costs, a more efficient use of building resources and services, good control of internal comfort conditions, effective monitoring and targeting of energy consumption.
  
• Stack effect controls: Great thermal differences between the building’s interior and exterior generate a stack effect. Burj Khalifa was designed to passively control these forces, reducing the need for mechanical means of pressurization while saving energy.

Learning from the design and construction processes of Burj Khalifa, SOM is currently applying similar technologies to new projects. For example, the new DMC Tower in Seoul will make use of the naturally occurring wind stack effect. By generating a percentage of the building’s power demand using wind turbines, the design will reduce municipal energy use to a fraction of a supertall building’s typical consumption.

Other supertall structures are also learning from Burj Khalifa. In the world’s tallest building, SOM has implemented new ways to increase structural and construction efficiencies while reducing material use and waste. Lessons learned from Burj Khalifa will help to decrease the environmental impact associated with construction and raw material extraction.