Installation Continues on Abu Dhabi's Spiraling Capital Gate Tower
July 20, 2009
Considered by some to be one of the world's most challenging buildings
under construction, the Abu Dhabi National Exhibition Company's
(ADNEC) Capital Gate project recently passed the halfway mark. The
tower, which leans 18-degrees westward-14 degrees more than the
Leaning Tower of Pisa-includes a giant internal atrium suspended
on the 17th and 18th floor; the façade comprises 23,000 square
meters of steel and glass elements spiraling skywards.
$35 million glass facade is the responsibility of Austria's Waagner-Biro,
which is handling the steel and glass engineering. According to
RMJM, the United Kingdom-based architectural firm that designed
the project, the façade will feature Cardinal C240 glass
that is being shipped from the United States straight to Abu Dhabi,
though at press time RMJM representatives could not confirm what
company is actually supplying the glass. (Editor's note: USGNN.com
contacted Cardinal Corp. for additional information, but at press
time had not received a response.)
The design of the building poses several challenges with regards
to planning, production and erection. In keeping with the triangular
configuration of the main supporting structure, more than 700 diamond
shaped glass panels will be prefabricated on site from triangular
tubes and lifted into position fully glazed. No two of the 12,000
triangular panels are alike.
Because of the tower's unique posture, the 35-story Capital Gate
is being constructed on top of a 2-meter deep concrete raft with
an extremely dense mesh of reinforced steel. The steel exoskeleton
known as the "diagrid" sits above an extensive distribution
of 490 piles that have been drilled 30 meters underground to accommodate
the gravitational, wind and seismic pressures. The design of the
central core, which slants in opposition to the lean of the building,
straightening as it grows, has never been attempted before.
diagrid technology has only been used on a few buildings, including
the Hearst Tower in New York, The Gherkin in London and the CCTV
headquarters tower in Beijing. The system requires less structural
steel than a conventional steel frame and is formed by creating
triangular structures with diagonal support beams.
The total weight of Capital Gate's steel is estimated to be around
21,500 tons. Its diagrid is subdivided into 722 elements and approximately
8,500 structural steel beams for the entire building. Each diagrid
element weighs approximately 15 tons.
The building's decorative 'splash' is designed to mimic a wave.
Besides providing an innovative sunshade for the Capital Gate tower
itself, the splash provides a new and creative treatment for the
roof of the existing grandstand canopy in the adjoining Abu Dhabi
National Exhibition Centre grandstand. The splash is a completely
independent structure made of structural steel I-beams fixed to
the main building structure.
"The unique nature of this building has meant that the teams
responsible for delivering Capital Gate have experienced some immense
challenges, which they have overcome through vision, ingenuity and
cooperation. There is nothing standard about this tower. Each room
is different, each pane of glazing is different and every angle
is different," says Simon Horgan, ADNEC group chief executive
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