Phase 3 The Capital Gate ‘Feature Tower’ is high quality iconic building located on the exhibition site. It is distinguished by a dramatic steel and glass facade with a striking organic form. With its cantilevered tea lounge and open air pool deck, it provides a unique presence on the skyline of Abu Dhabi and creates a memorable identity to the exhibition centre.
ADDITIONAL INFORMATION •The building has a diagrid especially designed to absorb and channel the forces created by wind and seismic loading. •A gigantic internal atrium, including a ‘tea lounge’ and swimming pool suspended 80 metres above the ground, has been constructed on the 17th and 18th floors, the halfway point of the 35 storey, 160 metre high tower. •The tower was developed by Abu Dhabi National Exhibitions Company (ADNEC). It forms the centrepiece of the Capital Centre development, an AED8 billion (£1.5 billion) business and residential micro city being constructed around the Abu Dhabi National Exhibition Centre. •Due to its unique design, each hotel room is unique in size and shape •Abu Dhabi’s first Hyatt hotel, ‘The Hyatt @ Capital Centre’. •His Excellency Sheikh Sultan Bin Tahnoon Al Nahyan, ADNEC’s Chairman is quoted as saying: “Capital Gate is a landmark development for Abu Dhabi and with this recognition the tower takes its place among the world’s great buildings. It is a signature building which speaks to the fore-sight of the emirate.” •The building’s form is meant to represent a swirling spiral of sand. •It was a deliberate decision to integrate with the National Day Grandstand – one of Abu Dhabi’s most historic structures. In this way, Capital Gate underscores the bond between the traditional and modern that is characteristic of Abu Dhabi’s developmental approach. •Due to the location, views from Capital Gate are extensive in all directions. •The façade glazing emphasizes the organic elements with diagonals spiraling up along the structural diagrid. This weaving pattern is further broken down with individual panes of glass in a complex mesh wrapping the entire building.
DESIGN FEATURES 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 storey, and staggered, one over another by between 300 mm to 1400 mm.
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-centre. It is also anchored to the ground by 490 piles which are drilled 20–30 metres underground.
490 foundation piles were driven 20 to 30 meters underground to support the structure and counter stresses. 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.
Diagrid systems - 1– External 1 – Internal Diagrid nodes - 702 external – 120 internal There are currently 12,500 triangular glass panes on facade There are currently 720 diamond shaped sections on facade The building has a total incline of 18°, 14° more than the Leaning Tower of Pisa. The tower overhangs from the base a total of 33 meters. The Cardinal façade is 51% more efficient than standard typical façade in restricting solar heat to the building. This reduces the energy consumption by HVAC system by 15%. The Capital Gate floor plates are stacked vertically up to the 12th storey after which, they are staggered over each other by between 300mm to 1400mm giving rise to the tower’s dramatic lean. Every one of the 12,500 panes of glass on the façade is a different size, although each pane is triangular. Floor plates change shape and orientation to create the distinctive “overhang” moving from “curved triangular” to “curved rectangular,” while increasing in overall size and migrating from east to west as they progress up the tower. Capital Gate is one of the few buildings in the world to use a diagrid structure. The Capital gate features 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. Due to Capital Gate’s unique shape, the upper half of the tower widens to create an atrium at the hotel’s guest room floors. The curved canopy, known as the “splash,” which rises on one side of the building, creates a wave-like effect, reflecting the building’s proximity to the water and the city’s seafaring heritage.
Capital Gate’s base structure is a vertical concrete core surrounded by a steel diagrid describing the external form of the tower. Steel beams span between the two, supporting metal deck and concrete composite floor slabs.
Above the base, the atrium is formed with an internal steel diagrid attached to the core. Steel girders span directly between the external and internal diagrids, creating column-free floor spaces with typical spans of about 12 meters.
The external diagrid is composed of hollow square sections 600 x 600 millimeters on a side. They carry floors four meters high. The external diagrid elements are made from welded steel plates, 80 millimeters thick at the bottom floors, and progressively lightening to 40 millimeters at the top floors.
The diagrid connections are nodes located at the floor slab levels where girders frame in. The external diagrid nodes are also designed for the façade panels to frame on the outside. Designers studied these connection details extensively to optimize construction, as well as structural integrity. The upper half of the tower has a double skin façade to reduce the solar heat gain at the hotel levels. This is a modified double façade, which recycles interior air from the guest rooms into the façade cavity. Here it creates an insulating buffer between the hot outside air and the cool inside air. The air is re-used in the room rather than exhausted and replaced with outside air. The ‘splash facade’ eliminates 30% of the sun’s heat before it reaches the building, reducing the air conditioning load on the protected floors. The concrete core occupies the only vertical space available in the tower profile. During construction a pre-cambered core was poured slightly off vertical, so when the tower floors were framed into the opposite side, the added load straightened the tower.
The tower includes many passive and active sustainable systems, including: •Metal mesh sun shading, •A double skin façade, •High-performance glazing, •vegetated roof on the basement, •Low-flow water fixtures, •District cooling, •Variable speed air conditioning, •Heat exchange for ventilation, •Energy monitoring and controls.
