How was Dubai's 828m-tall Burj Khalifa built?
Construction Week revisits the design and engineering nitty-gritty of Dubai's Burj Khalifa on its eighth anniversary
On 4 January, 2018, Dubai celebrates two momentous occasions.
For starters, the date represents 12 years of HH Sheikh Mohammed Bin Rashid Al Maktoum's leadership as the Ruler of Dubai.
The date also marks the eighth anniversary of the world's tallest tower, Burj Khalifa.
In the years since its 2010 opening, Burj Khalifa has put Dubai on the world map, and become a core ingredient of the Emirate's global brand identity.
Its 148th floor observation deck, unveiled in 2014, was officially declared as the world’s highest when opened.
In March 2016, a spiral staircase that takes Burj Khalifa's 555m-high observation deck to another level was revealed.
Level 125 is now part of the At the Top Burj Khalifa Sky journey that takes visitors to the world's highest observation deck on Level 148.
The spiral flight is built with 60 metric tonnes of steel, 700sqm of glass, and 350sqm of stainless steel cladding.
While the UAE and indeed, the GCC, has witnessed the development of numerous other landmark towers since the Burj Khalifa's launch, the global design, architecture, and construction spotlight has remained firmly fixated on the 828m Dubai landmark for the engineering marvel it is.
As Burj Khalifa celebrates its eighth anniversary, Construction Week takes a look at the tower's key statistics and achievements since its opening.
2010: The Grand Opening
Vision is a word you hear a lot in the GCC. But just imagine if you will, sitting down in a meeting and deciding to construct the world’s tallest building in your city. Not one that is going to be the tallest by a few dozen metres, and relinquish its title to another tower, in another city, within a few years, but the tallest by a massive margin.
If you can imagine that, then you can get a feeling for the vision that went into coming up with the Burj Khalifa, officially the world’s tallest tower, a whopping 200m-plus taller than the next nearest rival. More than six years in the making and not fully-finished just yet, the project was and is a massive undertaking, one that has paired bold vision with a brave leap into the engineering unknown.
Making it happen not only needed vision, but cash as well as design and engineering genius. Pushing at the envelope of engineering means trying new things, developing new techniques and carrying out rigorous rounds of testing.
And while it’s hard to find a construction contractor or supplier who doesn’t claim to have been involved in the making of the Burj Khalifa, CW takes a look at what those who were really there had to do to build an icon.
Next page: Finance, Design, and Foundations
Once you’ve had the vision, the real work doesn’t start until you find a way to pay.
Mohamed Alabbar, Emaar chairman, in January 2010, suggested a final budget of $1.5bn. Mashreqbank, Emirates Bank International, and Abu Dhabi Commercial Bank formed a syndicate to provide finance way back in 2005.
The triumvirate of banks signed a financing agreement with Korean contractor Samsung Corporation and its project partners Belhasa Six Construct and Arabtec. The good news is that around 90% of saleable space was sold off-plan, helping ensure that money never ran tight.
Skidmore, Owings & Merrill was the architecture firm behind the design and engineering of the tower.
The design team developed what has become known as a spiraling “Y” shaped plan, which was used to shape the structural core of the building.
Key considerations included the impact of wind forces and ‘constructability’, architecture cant for practical construction considerations. The design employs a ‘buttressed core’, which has each wing of the building buttressing the others via a six-sided central core.
It is this central core that provides the structure’s torsional resistance. The design of wall and corridor intersections means that all of the vertical concrete is used to support both gravity and lateral loads.
As the building spirals in height, the wings set back to provide many different floor plates. 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 disrupting the flow of the wind over the height of the building.
If you want to build high, you must first dig deep, driving foundations down well below the surface. The tower’s superstructure is supported by a large reinforced concrete mat, which is in turn supported by 192 bored reinforced concrete piles.
The mat is 3.7m thick, and was constructed in four separate pours totaling 12,500 cubic metres (m³) of concrete. Bauer Spezialtiefbau, with Middle East Foundations, took on much of the piling work, which required bores to be sunk for cast in-situ piles, to a depth of 43 metres.
Known by some as the ‘Rolls-Royce’ of the drill rig world, the Bauer BG40 can deliver, as the name suggests, 40nm of torque.
Around 45,000m³ of concrete, weighing more than 110,000 tonnes, were poured for the foundations – that’s equivalent to 18 Olympic sized swimming pools – with 192 piles running to a depth of over 50m.
Next page: Concrete and steel, Pumping, and Cladding
Concrete and steel
You know already that over 45,000m³ of concrete was used to in construction of the tower’s foundations. The overall construction process will have used 330,000 m³ of concrete and 39,000 tonnes (43,000 ST; 38,000 LT) of steel rebar. Laid end to end, the rebar used in the tower would extend over a quarter of the way around the world.
For the construction of the tower, BASF developed a special concrete mix that was pumped to a height of more than 600 metres (see ‘Pumping’) without segregating. Thanks to BASF’s admixture Glenium Sky 504, the concrete could be worked on for more than three hours before hardening took place.
This allowed for a shorter construction time and gives the building a longer useful life, making it more sustainable.
In November, 2007, the highest reinforced concrete corewalls were made using concrete pumped from ground level to a vertical height of 601m. This broke the previous pumping record for a building of 470m on the Taipei 101 and the previous overall world record for vertical pumping of 532m for an extension to the Riva del Garda Hydroelectric Power Plant in 1994.
The concrete pressure during pumping to this level was nearly 200 bars.
The mix was able to reach such astounding heights by running through a high-pressure trailer mounted pump (a Putzmeister 14000 SHP D). The concrete required approximately 40 minutes from the filling of the hopper to its discharge from the delivery line.
The concrete volume in the line amounted to approximately 11m³ with this installation height – meaning there was roughly 26 tonnes on the pump after every piston stroke – or five big elephants.
Over a period of about 32 months, the high pressure pump and two others delivered more than 165,000m³ of high-strength concrete, which, using our preferred unit of measurement, is about 66 Olympic sized swimming pools.
Next page: Cranes, Dismantling, and People
They’re graceful, mysterious and it seemed for a time everybody’s favourite topic. The high level cranes at Burj Khalifa were always enigmatic.
Three Favelle Favco cranes served right up to level 156.
Given that the machines worked 24 hours for much of the project’s duration it would be safe to assume that there was a team of at least nine drivers and many other technicians to ensure safe operation.
Usually, the cranes’ loads consisted of steel reinforcement beams, but welding equipment, scaffolding, gensets, and even tanks of fuel for the diesel powered cranes all needed to be lifted to the correct floor.
Installing the three high-level cranes was relatively straightforward as sections of the cranes could be moved up the tower with the completion of new levels.
Getting the towers down however, required a little more lateral thinking. The first high-level crane was moved in November 2007 down to level 99 in order to serve as a future recovery crane.
The next high-level crane came down in October 2008, leaving one prominent machine at the top.
Another small crane had to be lifted to floor 159. With a crane on this floor as well as the one on level 99, the dismantling process was ready to begin. The process started with the crane climbing down from its working height of over 700m.
The crane removed its own mast sections and lowered them to the ground until the boom and power pack were at the position of the Level 159 recovery crane.
From there, the Level 159 recovery crane dismantled the remainder of the main crane, lowering the pieces of boom, mast and power pack to the recovery crane at Level 99, which further lowered them to the ground.
The dismantling of the cranes at Burj Khalifa was indeed a finely orchestrated set piece – except that the artists here were huge machines.
The three cranes on the tower were all diesel Favelle Favco units, of various specifications.
This type of diesel-hydraulic crane is popular on ‘supertall’ skyscrapers, due to a useful turn of speed and power.
Burj Khalifa was an international collaboration between more than 60 contracting and consulting companies from all over the world.
At the peak of construction, over 12,000 workers and contractors were on site every day, representing more than 100 nationalities.
Next page: MEP and people-flow
The mechanical, electrical, and plumbing (MEP) services for Burj Khalifa were developed in co-ordination during the design phase with the co-operation of the architect, structural engineer, and other consultants.
Hyder Consulting was appointed as a supervision consultant with responsibility for overseeing execution of the MEP. An ETA-Hitachi-Voltas joint venture was awarded the building’s MEP contract.
Seven double-storey mechanical floors housed the equipment that brought Burj Khalifa to life. Distributed around every 30 storeys, the mechanical floors housed the electrical sub-stations, water tanks, pumps, and air handling units that were essential for the running of the building.
These mechanical areas typically serve the 15 floors above and below them. The primary distribution route for services is through the main risers within the central core of the structure, which remains the same size to level 150 despite the overall building shape tapering with height.
Elevators and lifts
The Burj Khalifa features distinct sections: residential apartments, serviced apartments and hotel rooms, and corporate offices. Elevators have been arranged in zones to serve these different audiences, with what is known as a ‘sky lobby’ system.
The sky lobby is an intermediate floor where residents, guests and executives will change from an express elevator to a local elevator, which stops at every floor within a certain segment of the building. Burj Khalifa’s sky lobbies are located on level 43, 76 and 123 and will include a lounge area and kiosk, amongst other amenities.
All elevators have been supplied and installed by Otis. No elevators are installed to travel all 160 floors of Burj Khalifa. Instead, they are grouped to align with the floor layout, offering passengers a direct express service to their destination by bypassing other floors.
The main service elevator, positioned in the central core of Burj Khalifa, has the world’s highest elevator rise at 504m – more than the height of Taipei 101 in Taiwan (448m). It travels at nine metres per second and also has the world’s longest travelling distance for an elevator.
Next page: Podium and access, Landscaping, and Fitout
Podium and access
The podium provides a base anchoring the tower to the ground, allowing access from three different sides to three different levels of the building.
Fully glazed entry pavilions constructed with a suspended cable-net structure provide separate entries for the Corporate Suites at B1 and Concourse Levels, the Burj Khalifa residences at Ground Level and the Armani Hotel at Level 1.
The number of underground car parking spaces is reported to be 3,000, which suggests that the owners are keen for people to use the nearby metro station and downtown light railway for access.
At the foot of the mighty Burj sits the ‘The Park’, an 11ha expanse of gardens, trees and water features. What is perhaps most noteworthy about The Park is that is irrigated using a water collection system that recovers the condensation from the tower’s cooling equipment.
This provides the park with around 15 million gallons of water a year – or enough to fill 20 Olympic-sized swimming pools. The Park was designed by SOM, designer of the tower itself, and SWA Group of California. WET, the designers of The Dubai Fountain, developed the park’s six water features.
The interior design of Burj Khalifa’s public areas was done by the Chicago office of Skidmore, Owings & Merrill LLP and was led by award-winning designer Nada Andric. It features glass, stainless steel and polished dark stones, together with silver travertine flooring, Venetian stucco walls, handmade rugs and stone flooring.
Over 1,000 pieces of art from prominent Middle Eastern and international artists adorn Burj Khalifa and the surrounding Emaar Boulevard. Many of the pieces were specially commissioned by Emaar.
The two main contractors for the interior fitout were DEPA and Fino International.
Next page: Spire and Window Washing
The crowning glory of Burj Khalifa is its telescopic spire comprised of more than 4000 tons of structural steel. The spire was constructed from inside the building and jacked to its full height of over 200m (700ft) using a hydraulic pump.
In addition to securing the Burj Khalifa's place as the world's tallest structure, the spire is integral to the overall design, creating a sense of completion for the landmark. The spire also houses communications equipment.
Access for the tower's exterior for both window washing and façade maintenance is provided by 18 permanently installed track and fixed telescopic, cradle equipped, building maintenance units. The track mounted units are stored in garages, within the structure, and are not visible when not in use.
The manned cradles are capable of accessing the entire facade from tower top down to level seven. The building maintenance units’ jib arms, when fully extended, will have a maximum reach of 36m with an overall length of approximately 45m.
Next page: Milestones, World Records, and Fantastic Facts
- Record base jump broken off Dubai's Burj Khalifa
- Hollywood actor Tom Cruise etches message on Burj Khalifa
- Entire Burj Khalifa floor goes on sale
- French Spiderman conquers the Burj Khalifa
At over 828m and more than 160 stories, Burj Khalifa holds the following records:
- Tallest building in the world
- Tallest free-standing structure in the world
- Highest number of stories in the world
- Highest occupied floor in the world
- Highest outdoor observation deck in the world
- Elevator with the longest travel distance in the world
- Tallest service elevator in the world
- 28,261 Glass cladding panels make up the exterior of the tower and its two annexes.
- 1325 Days after excavation work started in January 2004, the Burj Khalifa became the tallest free-standing structure in the world.
- 12,000 Workers and contractors were on site every day at the peak of construction.
- 124 Storeys up is the publicly accessible observation deck, with an outdoor terrace.
- 606 Metres is the height to which concrete was pumped, a world record for concrete pumping.
- 504 Metres is how high the Burj Khalifa’s main service lift travels, the most of any elevator.
- 57 Elevators will move occupants around.
- 31,400 Tonnes of rebar were used in the structure of Burj Khalifa.
- 5,500 KG is the carrying capacity of the service lift