Providing sheer scale and spectacle, creating world firsts and the emphasising the importance of the human factor, are all vital to the success of a towering structure.
And each of the challenges of creating a supertall were addressed at an architectural roundtable which took place at Cityscape Global in Dubai.
Taking the lead were the world’s two top high-rise designers, Adrian Smith and Gordon Gill, whose partnership AS + GG has been selected to design Dubai’s Burj 2020 skyscraper.
Both are currently working on Saudi Arabia’s 1km-tall Kingdom Tower and Smith designed the building which holds the record for the tallest on Earth – Dubai’s Burj Khalifa.
As the forum started Smith explained that it was at Cityscape 2006 that his partnership with Gill received its first project – the Burj Vista which “sat on the shelf for five years” but is now under construction. He said he felt it was appropriate, as well as exciting, that the firm was now embarking on a new architectural adventure. Smith said: “We feel very fortunate to have participated in the competition for the DMCC [Burj 2020] tower and we have been selected to move forward to develop the tower and to help the masterplan – and the buildings around the masterplan – to be formed into a portion of the larger district.
“I think that’s a very important ingredient to form those seven buildings plus the podium and the base to be a family, where each building will participate in the activities of the mixed-use complex.”
The architects explained that the project is still in its early stages and demand for space will dicate exactly how tall it will eventually be.
Smith told the meeting: “You will notice that the model is pretty abstract and it is abstract on purpose because it’s at a conceptual level – not all buildings have been fully designed yet.
“But we are working on that and we are also working on the tower in terms of mechanisms to increase the structure and decrease the structure from a size point of view.” The architects said each building will reinforce the design and use of the other ones outlined in the masterplan.
Smith then outlined the challenges faced by designers of supertall structures and how increasing the height of a skyscraper also increases factors which need to be taken into account.
He said: “One of the aspects of supertall towers is that it’s a science, in and of itself. It’s different. The difference between a 20 storey building and a 50 storey building is not a very keeling [possibility of tipping over] difference from an engineering perspective. But when you start going from 100 storeys plus….we like to say in the industry that 300m is where you begin to get into the supertall category of design.”
The movement of the earth and possibility of tremors then become huge factors in design and construction, Smith told the conference.
He explained: “What happens is that the forces on the building no longer become gravitational only. They are gravitational but there are also horizontal forces within the movement of the earth.
“So these horizontal forces that play on the building have a significant impact on how the building gets designed and engineered. So most supertalls that you see, you will learn that the form matters in terms of the performance of these towers from an engineering perspective.
“If they are tapered, that helps, if they are stepped, that helps. If they are straight up and down, that hurts. In other words, if they are straight up and down they will use more structure per square foot as they need to battle horizontal forces than if they are tapered or stepped.
“When the wind is blowing at the building the natural inclination is to think that it will blow it over. What happens is that the wind has to get around that building and as it blows around that building it starts moving sideways and so starts to combine with the wind that is also moving past the building and so achieves higher speeds.
The architect said this begins to create a vortex on the side of the building and at its back and the air then rushes in to fill that void – just as a stream creates ripples and eddies as water flows up to and past a rock.
“So if you look at a rock in a moving stream, you will see how the water eddies in advance of those rocks, and it’s the same thing with buildings,” said Smith.
“But it does it all the way up the building. If it’s a consistent eddy it can build up – that force can build up on the building. So if you taper the building, or if you manipulate the profile of the building, then that eddy changes from floor to floor and therefore the forces are mitigated. They are reduced and that in turn reduces the quantity of steel and concrete.
“So these are just some of the things that make supertall design and engineering different.”
Islamic forms are an important part of the design of the high rises the architects have worked on in the Middle East region.
The Burj Khalifa incorporating the traditional arch is an example of this, Smith said.
Gill emphasised how cutting carbon emissions was also an important part of the design of a high rise – so the most efficient use of concrete which is ever improving was an important factor.
He also told the group that the human factor was vital in ensuring that even the most ambitious project was fully fit for purpose.
“The building needs to have a community feel as it is bringing people into a space,” Gill said. “The client in the case of the Burj 2020 has been rigorous in ensuring we capture a quality of scale as we bring the building down to the ground. That is a fantastic quality and it is also one which is frequently overlooked.”
He said the aim of the team was to provide the best possible environment for people to live life to their fullest, with the use of as much innovation to promote sustainability as possible.
“The question is – can we deliver that?” he said. “We don’t want to compromise people’s way of living. We don’t think we have to take something away from people’s quality of life to deliver a sustainable design.”
Smith said the new tower will be another major architectural icon for the city of Dubai.
“This can become one of the great places in the world and we are striving to make it a great world centre, for living, working, entertainment, shopping and relaxing,” he said.