Gulf Construction Online - Round icon wins applause

Round icon wins applause

As Abu Dhabi’s latest icon opens its doors, Gulf Construction delves into its design and construction in a special project report.

01 May 2010

OVER the last three years, visitors and passers-by at one of Abu Dhabi’s newly-developed beachfronts in Al Raha would have watched with great interest as a unique structure rose beside the sea like some futuristic flying saucer poised for take off or coin standing on its diameter.

Now, with the tower nearly complete, they will soon be visiting and admiring this spherical 110-m-high landmark from Aldar Properties, one of Abu Dhabi’s premier real estate developers, when it opens its doors later this year.
Built at a cost of Dh950 million ($258.8 million) and christened ‘HQ’ – as it will be home to Aldar’s headquarters – the tower enters the record books as the first spherical building in the Middle East.

From concept to completion (top) ... HQ is a new landmark on Abu Dhabi’s skyline.

Aldar’s brief for MZ Architects was challenging but precise: it wanted a building that would combine its architectural aspiration for an iconic headquarters and the requirements of a high-end office tower for regional and international clients.
Green design was also part of the brief: it had to achieve Silver certification under the Leed (Leadership in Energy and Environmental Design) environmental classification system awarded by the US Green Building Council (USGBC).
Main contractor Aldar Laing O’Rourke started work on the project in April 2007, and is currently testing and commissioning the tower ahead of handing it over to Aldar this month.
HQ boasts a prime location, at the heart of Al Dana precinct, the central business district of Aldar’s Al Raha Beach development located off the main arterial road network linking Abu Dhabi to Dubai. Set upon an elevated peninsula and offering spectacular views of the city, canal and sea, Aldar says HQ will provide an “unrivalled working environment” through the integration of exceptional services and facilities as well as proximity to leisure and retail outlets located throughout the development.
HQ offers 50,086 sq m of premium space over a podium containing five levels of parking. The average footplate area per floor is 1,600 sq m, going up to 2,700 sq m from the ninth to 13th floor.
It features 21 storeys of offices, a top-floor exhibition and general function area (level 23), two cafes at the ground and mezzanine levels overlooking the reception area, three retail kiosks in the external podium area accessed from the promenade and four levels of the basement car parking (five levels to PC813, adjoining the parking lot) offering slots for 1,225 vehicles. The car-park – restricted to tenants and guests – is accessed from the ground floor via a 4-m-wide ramp. A barrier will be located at the entrance, allowing access via a card reader.
The basement levels also house essential services such as a substation, a generator room, a refuse compacting room, water tanks and pump rooms.
Other facilities include prayer rooms for men and women and gymnasiums with shower facilities.

Design
The design objective was to achieve a cost-efficient building that allows spatial requirements to be met whilst respecting the form of the building and permitting the creation of the strong visual shape. The design is sufficiently robust to facilitate future fit-outs by tenants and provide significant areas of flexibility where possible.
The building comprises a steel frame rising up to 23 storeys and connected to two large concrete cores to transfer the loads of the exterior weight. It has a diameter of 120.9 m with its width varying from 10 m at ends to 36.4 m in the middle.

Tight deadlines ... the project team worked closely together, using advanced 3D models developed by Arup.

HQ’s elegance belies its complex steel structure and super-fast construction schedule. To meet the tight deadline, the project team worked closely together, using advanced 3D models developed by Arup, a leading global firm of consulting engineers. Its striking shape is achieved through the use of a structural diagrid – a diagonal grid of steel – which largely eliminates the need for internal columns to support the building. The result is spectacular, uninterrupted views of the city and coastline through fully-glazed facades.
The building includes several complicated elements such as peripheral diagrid columns, an outer ring, an internal ring, central ring columns, diagrid nodes, and a plane truss connecting the outer, internal and central columns at all floor levels. The roof is an integral part having primary beams in line with the columns.

Sleek design ... side angle of HQ.

The central diagrid on the east elevation at ground floor level provides access to the building through an entrance vestibule that follows the diamond shape. The entrance is mirrored on the west elevation, creating a unique footprint. The dual entrance leads visitors to a double-height reception lobby. Reception desks and security barriers are located at each entrance.

Construction
Built to international Grade A standards, HQ sits on reinforced concrete (RC) piling connected to suspended RC slabs. The superstructure comprises RC slipformed core and steel frame while the flooring consists of steel superstructure with composite metal deck floors.
Steel-frame superstructure forms the curved shape of the main façades, laterally braced to two RC slipformed cores with suspended composite metal deck floors.
Various strengths of concrete have been used to suit the application, ranging from C40 to C70.
The external facade comprises a double-glazed, panel façade system with solar-reflective and low-emissivity coatings.
The facade was analysed and glazing options were investigated in order to develop the most efficient strategy for production and construction purposes. A series of studies were carried out in order to find a geometric shape that enables the most efficient unitising of glazing units, while maintaining the aesthetics of the form and shape.
At the concept stage, each facade consisted of 5,821 glazing units with a total of 11,642 individual glazing units. Overall, there are 1,451 sets, each consisting of eight identical glazing units. As a result, it was necessary to increase the unitising of the glazing in the schematic design process.
In adherence to Leed guidelines, the building features extensive use of recyclable materials, and prefabricated elements to ensure minimum waste creation and an automated vacuum waste system – the first of its kind in Abu Dhabi – to aid in recycling waste materials.

Finishes & features
HQ features world-class finishes throughout all common areas incorporating natural materials. The ground floor reception and lift lobbies feature Calacatta marble flooring, skirting, Portuguese limestone wall cladding and suspended plaster-board ceilings.
Typical floor lift lobbies feature Calacatta marble flooring, skirting, glass and stainless steel wall panelling and a suspended plasterboard ceiling.

Blueprints ... the basement and floors (below).

The office levels (Category A) feature 150-mm raised access floors, plasterboard wall and column cladding and 600 by 600 perforated metal ceiling tiles.
The basement car-park has an elastomeric floor finish, skirting and anti-carbonation paints for the walls and columns.

Landscaping
The area around HQ has been extensively landscaped with an elliptical-shaped pool at the entrance and two pedestrian paths cutting through the water feature, enhancing the vibrancy of the plaza as well as offering pedestrians a different perspective of the project.
There is continuous paving across the forecourt (warm and cool grey granite tones) and water features. The paving pattern evokes the facade of the building in plan, with the ‘diagrid’ spreading down throughout the plaza and stretching across the landscape.
Clever use has been made of lighting to highlight and enhance the landscape features. Creating an appropriate landscape for the project was no small feat. The design team’s goal was to provide a strong impact that relates to the scale and significance of the building.

“The aim has been to frame the building setting with a generous soft landscape zone to the perimeter of the site,” explains an Aldar spokesman. “While providing a buffer zone around the site, it also creates a rich, lush landscape with a pool of water at the centre. The play of softscape versus hardscape and a water feature intermediating between the two provides for a subtle complementary landscape.”
In addition, two observatory decks provide splendid look-out points to the various parts of the precinct. A mooring dock will be added at the northeastern corner of the site to provide for an arrival point via marine transportation, thus extending the accessibility to the site.

Challenges
HQ presented a challenge right at the outset of construction because of the high water table in the area. The builders had to drive piles from the ground level and work without the support of a diaphragm wall at the southern elevation.
There were other challenges. The late appointment of the BMU (building maintenance unit) contractor and lack of pre-construction services for this package led to co-ordination tangles with the façade and steelwork interfaces which had to be resolved on site, the spokesman explains. The roof’s unique geometry made it necessary to design a special BMU as well.

Uninterrupted views ... HQ uses structural diagrids, eliminating the need for internal columns.

To meet the project’s deadlines, work on HQ continued through the hot and humid summers and in shifts during the months of Ramadan. “The project team worked closely together and this allowed a significant overlap between the design and construction phases,” he explains. “Within three months of the design team’s appointment, piling work had started on the site. The concrete cores were completed within a year, and the steelwork had risen to the fourth floor within 14 months of the launch of construction.”
This collaborative approach allowed lead consultant Arup to design the building with the most efficient means of construction in mind. Concrete elements such as stairs and columns were precast while bathrooms were prefabricated.
“This not only saved time, but also improved quality, because the fitters did not have to work around other parts of the construction,” the spokesman says.
As Aldar gears to open HQ, its designers and builders can take pride in having succeeded in creating a stunning visual icon for Aldar.
But more importantly, behind the superlatives and the plaudits – HQ won the Best Futuristic Design award at the 2008 Building Exchange Conference, and was also a winner at the 2009 Arabian Commercial Property Awards in two categories – lies a functional office tower built to world-class standards that will add to the stature of Abu Dhabi as an international destination for business.

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