In Arabic, the name “Burj Dubai” means “The Tower of Dubai.” Presently the building is over 1800 feet off the ground, making it officially the tallest building in the world, surpassing the Taipei 101 building in Taipei, Taiwan, at 1667 feet. The total height of the building upon completion is still a secret. What is known is that it will be substantially taller than any other building currently standing. To provide some added perspective to just how tall the building will be, George Efstathiou, managing partner for Skidmore, Owings, & Merrill (SOM), Chicago, says that if you put the Hancock building in Chicago on top of the Sears Tower, the Burj would be approximately the same height.
Along with the Trump International Hotel and Tower construction in Chicago, the Burj is a structurally reinforced concrete building. Structural concrete may be the material of choice for all future super-tall buildings (buildings more than 80 stories tall) because concrete systems have twice the dampening effect compared to steel due to its increased mass, according to Bill Baker, the structural engineering partner at SOM. Reducing the force in super-tall buildings caused by wind is important. Baker adds that you can add dampening devices to the tops of buildings but they are expensive, must be maintained, and consume valuable retail space.
Another reason for using concrete is that in-place costs have become much more competitive with steel. Baker credits the changing technology in forming, placing, and concrete mixes for making the difference.
Doka is supplying the core forms for the project and the core structure forms are self-climbing. They also support the placing booms, which rise as the forms rise.
In order to reduce floor height requirements, most of the floors in the building are “flat plate,” meaning that slabs are even thickness. In order to do this work, the forms must be versatile and erect very quickly.
Concrete placement for tall buildings also has taken great steps forward with recent developments in concrete pumps and placing booms. Putzmeister, Stuttgart, Germany (Sturtevant, Wis., in the United States), supplied the pump for the Burj, which moves concrete in a single lift to the top of the building. Pumping is much faster than lifting concrete with tower cranes, plus the cranes are free for other work.
Improvements in concrete mixes, including both strength and modulus of elasticity, have made concrete high-rise construction more attractive. Baker believes that the modulus of elasticity of a mix is as important as its compressive strength for super-tall building work. Self-consolidating concrete is playing a greater role in high-rise construction as well—needed because of reinforcing steel congestion and ease of placement. At the Burj site, soils are very corrosive, having both high chloride and sulfate contents, so high-performance, dense concrete is a must.
The idea to build the Burj started in 2003 when Emaar Properties, Dubai, decided to develop a new central downtown area. The centerpiece for the project would be a super-tall building surrounded by a huge surrounding mixed-use development comprised of residential, commercial, hotels, entertainment, shopping, open green spaces, water features, pedestrian boulevards, and tourist areas. Efstathiou says that Emaar invited five architectural firms to submit design ideas for the building, choosing SOM to do the work. The original thought was to make it the tallest building in the world; but only slightly taller than Taipei 101. The building became even taller as the design progressed.
One of the great differences between designing super-tall buildings and low-elevation structures is managing wind forces, or to use a more technical term—vortex shedding. Wind vortices around a building can cause it to move from side to side at right angles to the wind, says Baker. This can be countered by altering the width and shape of floors along the height of the structure.
SOM managed wind forces on the Burj by spreading out the base of the building to three wings, which SOM is calling a buttressed core system, providing support for the structure regardless of the direction of the wind.
Concrete work for the structure will top out late in 2007. Then a structural steel “pinnacle” containing communications will be added to the top. With this complete, the total height of the building will be made public for the first time. The structure will be complete and ready for occupancy in 2009.
- Number of stories: 160
- Total height of building: TBA
- Project square footage: 5 million square feet
- Square footage of concrete wall construction: 4,628,482 square feet.
- Cubic yards of concrete: 300,000 cubic yards (equivalent to a 200-foot cube, 1200 miles of sidewalk, or the weight of 100,000 elephants)
- Steel reinforcement: 31,400 metric tons
- Current days to complete one floor level: Three
- Owner: Emaar Properties, Dubai
- Architect/engineer: Skidmore, Owings & Merrill, Chicago
- Project management: Turner Construction International, Dubai
- General contractor: Samsung, Seoul, South Korea
- Forms manufacturer: Doka, Lawrenceville, Ga.
- Concrete pump: Putzmeister, Stuttgart, Germany