“It was the first time that we’d undertaken a project of this complexity and so there was an element of trial
and error. But we augmented the team and added more resources. The client has never worked on anything like this either, so we were all on the same learning curve. Capital Gate was all designed from first principles, which was both a challenge and very exciting at the same time.” He explains how the building required a unique collaboration between sub-contractors. “Normally, the politically
correct way to work with sub-contractors is to direct all communication through the main contractor, but with this project we had to use a unique approach. We all sat down together and talked everything through, right down to the nitty gritty details. We also held frequent informal workshops with small groups to talk through problems and identify challenges. It was a great collaboration and is the only way we could have made it work.”
MAKING IT HAPPEN
Like London’s ‘gherkin’ tower, by Foster + Partners, Capital Gate uses a diagrid structural system – a steel grid with diagonal support beams. Archibold says: “The diagrid has 728 elements, all unique, which are stacked and welded together to create the exterior skin. Currently there are no other diagrid buildings in the UAE. It is also the first fully asymmetric diagrid. “A standard column and beam design would’ve used 30 percent more concrete and steel, but the diagrid gives us a com- pletely clean floor plate. This means that the offices from floors two to 16 have a 360 degree panorama and 270 degrees of that are unobstructed. It’s only the core that gets in the way.” Yet he adds that the use of the diagrid also created challenges. “The fact that the network and system isn’t the classic column and beam made life really difficult for us,” he says. Johnson reiterates that the nature of the design resulted in immense engineering requirements. “The tower is not just leaning in one direction, it slowly rotates. The steel and piling requirements are immense. “To build something like this you need a lot of development to the structural steel design. There’s a concrete core but stemming from that is structural steel. It’s a very complex design and it involved a lot of development, especially the glass façade.” Archibold adds: “All that weight is transmitted through
huge trusses which connect at just four points at the core. This perfect engineering is testament to the skill of the steelworks fabricators.” The team decided to make the raw power of the
steelwork a feature of the interior. Archibold says: “We wanted to the leave steelworks exposed and show off its muscular appeal and maximise on architectural detail. It’s a wonderful material and we didn’t want to cover it up – we just finished it with a fire resistant coat of paint.” Achieving the lean required an unconventional approach
to construction, which involved actual movement of the building core during the process. Archibold explains: “To accommodate the lean we built the concrete core at an angle. As we poured the floors, the centre of gravity of the building moved and pulled the core straight; so the whole building moved as it was under construction. We had to adjust the force on the lower floors using 80-millimetre thick steel, which is a phenomenal thickness.”
The movement of the building had to be considered when fitting the glazing. “It was like firing a rocket at the moon and planning the trajectory before the moon reached the launch position,” remarks Archibold. He continues: “Each pre-glazed exterior panel measures eight by eight metres and had to be dropped into place like a giant jigsaw puzzle. It all had to be delivered on site in the right order. Despite the size and complexity, the design enabled us to put one piece into place in just 30 minutes.” The high-specification glazing also eliminates the need for solar shading, as Archibold explains: “The exterior glazing
is a first for the UAE – it’s from the US and is a next-generation glass (Cardinal 240) that comes from a family of low- emissivity (LowE) glass. It has a silver coating which reduces glare yet doesn’t cut down the amount of visible light. This means that we didn’t need external shading devices.” Johnson adds: “I think the company responsible for the exterior glazing, Waagner-Biro, and the structural steel con-
tractors, Eversendai, have done an amazing job. Those panels are twisted and distorted and they all fit perfectly. It’s just amazing – I haven’t seen anything like it.” The building also has a double glass façade, which helps to reduce energy consumption. “Cooled air is trickled into the metre-wide gap between the layers to pre-cool the internal space. These geo-efficiencies reduce the overall cooling load on the building,” adds Archibold. Johnson reveals that that the twist and lean of the building created a major headache for the positioning of the Mechanical, Electrical and Plumbing (MEP) shafts. “Normally MEP riser shafts run vertically, but if the floor is stepping 700mm or so then the riser shafts can’t be vertical all of the time. This causes major engineering and build-ability issues. We overcame them but it wasn’t easy.”
6
LASTING LEGACY
The team’s passion and belief in the project is palpable. While standing outside the site office, Johnson remarks: “My favourite view of the building is definitely from this spot. It’s quite incredible.” ADNEC’s Vincent says that the citizens of Abu Dhabi are starting to share the team’s fascination with Capital Gate. “When
the building was halfway up, the odd car might stop. But now I see many people taking photos every day. People are beginning to recognise it. We’re seeing the wonderful process of people starting to love a building.” Archibold adds: “Capital Gate is a global benchmark. I’ve certainly never seen anything else like it and it’s on a par with
buildings such as the ‘bird’s nest’ Olympic Stadium in Beijing.” Vincent is convinced that the building will be a much-loved addition to Abu Dhabi’s skyline. “I genuinely think you
only get one chance in your lifetime to work on a building like this. I think Capital Gate will be an icon for Abu Dhabi like the Burj Al Arab is for Dubai.”
apr-may 2010
/ / 51
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68