Gulf's leaning tower

AN iconic 160m high building which will eventually lean further than the world famous Leaning Tower of Pisa is halfway to completion.

Abu Dhabi National Exhibitions Company (ADNEC) has announced the achievement of one of the most significant milestones in the construction of the iconic Capital Gate, adjacent to the Abu Dhabi National Exhibition Centre.

A gigantic internal atrium, including swimming pool and 'tea lounge' has been suspended on the 17th and 18th floors, the halfway point of the 35-storey, 160m high tower. The tower now stands approximately 100m high with the central core at level 22 and the external diagrid at level 18.

A diagrid (from diagonal and grid) is a design for constructing large buildings with steel which creates triangular structures with diagonal support beams. It requires less structural steel than a conventional steel frame and also removes the need for large corner columns and provides a better distribution of load in the case of a compromised building.

Well-known buildings which use this type of structure are the Hearst Tower in New York and London's beloved Gherkin - 30 St Mary Axe.

When complete Capital Gate will lean an astonishing 18 degrees westward, 14 degrees more than the Leaning Tower of Pisa. By installing a huge number of steel struts, engineers have realised ADNEC's and project architect RMJM's vision of the atrium - creating a cantilevered 'tea lounge' and swimming pool suspended 80m above the ground at level 18.

Because of its unique posture, the 35-storey Capital Gate is being constructed on top of a 2m deep concrete raft with an incredibly dense mesh of reinforced steel.The extraordinary steel exoskeleton diagrid sits above an extensive distribution of 490 piles that have been drilled 30 metres underground to accommodate the gravitational, wind and seismic pressures.

The design of the central core, which slants in the opposite direction to the lean of the building, straightening as it grows, has never been attempted before.

Commenting on Capital Gate's progress, Simon Horgan, ADNEC group CEO, said: "When complete Capital Gate will be a modern day icon for Abu Dhabi, recognisable throughout the world. Capital Gate is not about being the biggest or the tallest, it is about advanced technical ingenuity and aesthetic splendour. This is one of the most challenging buildings under construction in the world at the moment but due to the partnership between ADNEC, RMJM and all contractors on the project, ground breaking solutions are being designed on a daily basis."

Tony Archibold, RMJM project director, added: "Passing the half-way point in development is a great success and we are now entering a critical period in Capital Gate's development. While we are facing some of our toughest architectural challenges, it is also the beginning of the most exciting stage; where this unique structure begins to take shape."

Capital Gate will house Abu Dhabi's first Hyatt hotel - Hyatt at Capital Centre, a presidential style luxury five star hotel which will provide 200 hotel rooms and will serve ADNEC's visitors and exhibitors as well as international business and leisure travellers.