Capital gate

ADNEC is putting the finishing touches to its ‘gravity defying' tower in Abu Dhabi. Michael Johnson, senior project manager at ADNEC, explains.
Capital gate
By Middle East Architect Staff Writer
Wed 02 Jun 2010 03:09 PM

ADNEC is putting the finishing touches to its ‘gravity defying' tower in Abu Dhabi. Michael Johnson, senior project manager at ADNEC, explains .

Towering over the Abu Dhabi National Exhibitions Company (ADNEC) conference centre, the host of Abu Dhabi's Cityscape event, Capital Gate had a captive audience back in May.

The iconic tower, famed for its 18 degree lean -which is steeper than the Leaning Tower of Pisa - has been under construction since 2007, and all of the major work has now finished.  As of April 2010, workers at Capital Gate had clocked 6.5 million man hours, and at the peak of construction there were more than 1,200 workers on site.

The question on everyone's lips, of course, is how ADNEC got the building to lean. Michael Johnson, senior project manager at ADNEC, explains that the floor plates throughout the building are more or less the same size, and up to level 12 are stacked vertically on top of each other.

"Between levels 12 and 29 the plates stagger over each other, in relation to the lean and twist of the shell, by between 800 to 1,400mm and then back to 900mm - which is 4m floor to floor. Between the 29th storey and the 35th, the range is between 900 and 300mm in relation to the line of the façade," he said.

The lean, of course, puts immense pressure on the core of the building, which uses vertical post-tensioning to resist the stress. The core has been built with vertical pre-cambering and contains more than 15,000m3 of concrete reinforced with 10,000 tons of steel.Capital Gate's shell comprises a super-strong exo-skeleton called a ‘diagrid' that provides a clear, unobstructed floor plate, using much less steel than a conventional structural frame.  The external diagrid has more than 720 members with some of the heaviest weighing 16.5 tons.

All in all Johnson says Capital Gate was an ambitious and exciting project to work on.

"I have worked on some interesting projects in my career, but none of the others comes close in terms of complexity," he said.

"We have used techniques on this tower which have never before been attempted anywhere in the world,  such as the development of the world's first pre-cambered core. These are things that will be studied by students of architecture for years to come."

Work on the exterior façade of the tower is now complete, although the installation of the bridge that links to the Abu Dhabi National Exhibition Centre is still underway. ADNEC are now primarily focused on the interior of the projects, including kitting out 20,000m2 of office space and a 20,000m2  luxury Hyatt hotel.

"Interior fit-out of the hotel floors is currently ongoing, as is installation of all MEP services. Construction of the helipad is also ongoing and landscape design is expected to commence over the coming months," Johnson said.

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