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Capital Gate in 2013
|Type||Commercial offices; Hotel|
|Location||Abu Dhabi, United Arab Emirates|
|Construction started||September 2007|
|Owner||Abu Dhabi National Exhibitions Company|
|Roof||160 m (520 ft)|
|Floor area||53,100 m2 (572,000 sq ft)|
|Design and construction|
|Main contractor||Al Habtoor Engineering Enterprises|
Capital Gate, also known as the Leaning Tower of Abu Dhabi, is a skyscraper in Abu Dhabi adjacent to the Abu Dhabi National Exhibition Centre. At 160m(524.9ft), or 35 stories, it is one of the tallest buildings in the city and has been built so it inclines 18° to the west. The owner and developer of Capital Gate is Abu Dhabi National Exhibitions Company. The tower is a focal point of Capital Centre (Abu Dhabi)'s surrounding area.
- September 2007 – Enabling works commence
- November 2007 – Pile driving starts
- April 2008 – Core wall construction starts
- February 2009 – Façade commences
- May 2009 – Reaches 100 m in height
- June 2009 – Incline starts to take shape
- October 2009 – Attains final height of 160 m
- December 2009 – Completion of exterior core structure
- January 2010 – First phase of splash completed
- February 2010 – Interior fit-out commences
- March 2010 – Commencement of link bridge to Abu Dhabi National Exhibition Centre
- April 2010 – Commencement of atrium roof
- 2011 – Completed construction
- Opening date 21 Dec 2011
The structure sits above an extensive distribution of 490 piles that have been drilled 100 feet underground to accommodate the gravitational and wind force, as well as seismic pressures caused by the lean of the building. Of the total 490 piles, 287 are 1 meter (40 in) in diameter, and 20–30 meters (65–100 ft) deep; the remaining 193 are 600 mm (24 in) in diameter and 20 meters (65 ft) deep. All 490 piles are capped together using a densely reinforced concrete mat footing nearly 2 meters deep (7 ft). The piles, which were initially in compression during construction to support the lower floors of the building, are now in tension as the stresses caused by the overhang have been applied.
Core of the structure
The core of the Capital Gate was built using jumping form work. The center concrete core had to be specially designed to account for the immense forces created by the building’s lean. The core, which contains 15,000 m³ of concrete reinforced with 10,000 tons of steel, uses vertical post-tensioning and was constructed with a vertical pre-camber. This pre-camber means the core was constructed with a slight opposite lean. As each floor was installed, the weight of the floors and diagrid system pulled the core and slowly straightened it out. The core contains 146 vertical steel tendons, each 20 meters long, which are used for post-tensioning.
Given the 18-degree lean of the 160-meter Capital Gate, construction required two diagrid systems: an external diagrid defining the tower’s shape, and an internal diagrid linked to the central core by eight unique pin-jointed structural members. The external diagrid comprises 720 sections of varying shapes, as it is based on the direction in which the tower leans. The external grid carries the weight of the floor while the internal diagrid connects with the external and transfers the load to the core , thereby eliminating the need for columns in the floor.
In June 2010, Guinness World Records certified Capital Gate as the "World’s furthest leaning man-made tower." The new record shows that the Capital Gate tower has been built to lean 18° westwards; more than four times that of the Leaning Tower of Suurhusen. The Guinness World Record was given by a Guinness-appointed awards committee in January 2010, when the exterior was completed.
The gravitational pressure caused by the 18° incline is countered by a technique called pre-cambered core, using a core of concrete reinforced with steel, with the core deliberately built slightly off-center. It is also anchored to the ground by 490 piles which are drilled 20–30 meters underground.
Architecture and design
The building has a diagrid specially designed to absorb and channel the forces created by wind and seismic loading, as well as the gradient of Capital Gate. Capital Gate is thought[by whom?] to be the Middle East's first building to use a diagrid while others around the world include London's 30 St Mary Axe (Gherkin), New York's Hearst Tower, and Beijing's National Stadium.
The Capital Gate project was able to achieve its inclination through an engineering technique, known as pre-cambering, that allows floor plates to be stacked vertically up to the 12th story, and staggered, one over another by between 300 mm to 1400 mm.
- Capital Gate at Emporis
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- Mail Foreign Service (2010-06-10). "Abu Dhabi's Capital Gate 'leans nearly five times more' than Tower of Suurhusen to claim world record". Mail Online. Retrieved 2010-06-10.
- Laura Salmi (28 October 2008). "Capital Gate, Abu Dhabi, United Arab Emirates". World Architecture News. Retrieved 7 June 2010.
- Mace Group, http://www.macegroup.com/media-centre/advanced-diagrid-technology-gives-shape-to-capital-gate | retrieved=July 29, 2015