Increasing high-rise construction worldwide has led lift manufacturers to develop a double-deck or twin elevator design. With this, instead of the conventional one lift car per shaft design, two passenger cars are contained within the same shaft, using the same guide rails. Separate traction drives enable the two cars to travel to different floors simultaneously using the same set of guide rails. The passenger destination and direction of travel for the elevators is recorded at the start of all passenger calls and an electronic destination control system assigns the cars to the levels according to efficiency of operation. The electronic control also ensures that the cars never collide within the lift shaft. One of the major benefits of such a system is the reduction in service core space that is needed in a building by effectively combining two lift systems into one. Time saving for passengers is also a major advantage.
WORK ON BURJ KHALIFA PROGRESSED RAPIDLY AND HAD REACHED LEVEL 150 BY SEPTEMBER 2007.
EFRAIM EVIDOR/ITP IMAGES
FRANCISCO FERNANDEZ/ITP IMAGES
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FOUNDATIONS 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. Of course, there isn’t a situation that we could imagine where you would need such heavy power for drilling piling holes – half of this would be sufficient for
2008
2007 JULY 2007 Level 141 reached, making it the world’s tallest building AFP/GETTY IMAGES
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SEPTEMBER 2007 Level 150 reached KARIM SAHIB/AFP/GETTY IMAGES
CONSTRUCTION WEEK JANUARY 16–22, 2010
APRIL 2008 Level 160 reached, making it the world’s tallest manmade structure DMITRY DOLZHANSKIY/ITP IMAGES
OCTOBER 2009 AND WORK ON THE OBSERVATION DECK AT LEVEL 124 IS IN FULL SWING.
most situations. However, a reserve of torque means there is less stress put on the machine, so it can get on with what it is required to do. 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. A high density, low permeability concrete was used in the foundations, as well as a cathodic protection system under the mat.
2009
JANUARY 2009 Completion of spire; Burj Khalifa tops out ALEXANDER HASSENSTEIN/GETTY IMAGES