Mixed-use leaning tower
The Capital Gate is a 160m-tall leaning tower in Abu Dhabi, UAE. The tower inclines at an angle of 18° westward, 14° more than Italy’s Leaning Tower of Pisa.
The 35-storey building was designed by Robert Matthew, Johnson-Marshall & Partners (RMJM) and is used for mixed commercial purposes, including offices and retail spaces, the Hyatt Capital Gate hotel and a tea house.
It has 30 meeting rooms, conference facilities for 1,200 people, a business centre on the ground floor, a helipad and an eight-outlet food court.
The $231m project was developed by Abu Dhabi National Exhibitions Company (ADNEC). Construction work on the tower was started in September 2007 and was completed in 2011. Commercial leasing of the tower began in April 2011.
In September 2011, the project won the Best Commercial / Mixed Use Project and the Best Overall Project of the Year at the 2011 Cityscape Global Awards for Architecture in Emerging Markets. Capital Gate Hyatt was ready to start operations at the hotel in December 2011.
Capital Gate forms the centre of the $2.2bn Capital Centre, a 23-tower business and residential micro city being developed by ADNEC next to the Abu Dhabi National Exhibition Centre.
The tower is a two-layer design. The central core of the tower leans in the opposite direction to the inclination of the building and straightens with the height.
Advanced diagrid technology has been adopted for the building’s twisted design. It is the first tower in Abu Dhabi to use the technique. The building depends on the diagrid lattice arrangement of the façade which supports the tilting external load and provides structural integrity.
The technology used consumes less structural steel than conventional frames, reducing costs and environmental impact. A triangular structure with a diagonal support beam is used for the formation of the diagrid.
The technology has been used for structures such as the Swiss Re building in London, Hearst Tower in New York and CCTV headquarters tower in Beijing.
The building is constructed on a 2m-high concrete raft. The raft in turn is positioned on 490 piles, drilled 30m underground to withstand wind, seismic and gravitational forces caused because of its inclination. The basement for the tower has been densely reinforced and required a concrete pour of more than 6,000m³.
An 80m-long cone-shaped atrium is built through the upper floors of the building to form open balconies for the hotel rooms. The central core is constructed with pre-stressed concrete using automatic climbing formwork. The total built-up area of 53,100m² includes a basement of 5,500m².
About 21,500t of steel is estimated to have been used for the construction of the tower. The diagrid of the entire building is approximately 8,500 structural steel beams. Each diagrid weighs about 15t and is divided into 722 elements.
The east side has a decorative splash, designed in the form of a wave, connected with the canopy of the adjoining Abu Dhabi National Exhibition Centre grandstand canopy. The splash provides sun shade for the Capital Gate tower and a roof treatment for the centre’s grandstand.
The façade of the building is made of glass and steel elements which spiral skywards. The glazed panels give a striking effect to the 23,000m² façade. It is connected to the concrete core with steel structures.
The 728 custom-made glass panels fit the considering curvature of the building and form diamond shape. The glazing system, called Cardinal C240, is made of two silver coatings which are transparent, increasing its light transmission.
The 16 lower floors with 15,000m2 is used for offices, while the upper 16 levels house Abu Dhabi’s first Hyatt International five-star hotel and occupy 25,000m2.
The 17th and 18th floors – the halfway point of the building – are constructed with a gigantic internal atrium. It has a cantilevered tea lounge and a swimming pool suspended 80m above the ground on the eastern side of the façade.
The top of the lounge is an open sun terrace which gives a clear view of Abu Dhabi and the Gulf.
Al Habtoor Engineering Enterprises was the main contractor involved in the construction of the Capital Gate. Mace Group was the project manager.
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