Foster+Partners breaks new ground with the Living Wall concrete creation.
Few architectural sites in the world are as striking as Petra in Jordan. The iconic location is known around the world for its rock-hewn forms and is now designated as a UNESCO World Heritage Site.
Its backdrop undoubtedly posed challenges to the architects of the time. Now, some two thousand years later, a Foster+Partners project in Amman is similarly defying the problems posed by sheer rock.
Living Wall is a 150,000m2 mixed used complex located in the Jordanian capital, close to the new Al-Abdali city centre. The site is a carved-out rock shelf, with a sheer 30m backdrop.
The living wall
Taking cues from the raw rock in which the project will sit, the project will consist of six interconnected towers, which have been designed to emulate and empathise with their surroundings.
The project is based around the idea of bringing something still to life; the slope of the urban Wadi in which it is located. Hence the name, 'Living Wall'.
The project sits on a rough-hewn podium cut into the rock face, featuring strong, vertical incisions into a line of natural rocks. The Foster+Partners design envisages a community that appears to grow out of the very rock in which the towers are embedded.
Spaces between the towers will be shaded, so these are to be used as public spaces, sheltered from the heat of the sun. The public spaces will include a sunken amphitheatre and a large piazza. Meanwhile, creeping up from the shady depths, the towers will host shopping facilities, residential areas and a boutique hotel.
The towers have double-skin facades with screens, whose horizontal lines recall delicate rock strata.
This aesthetic design also serves a practical purpose: The screens stimulate air circulation and provide shading, which becomes denser in areas with the highest potential heat gain.
"[They] will store overnight coolness to create a comfortable work environment," says George Keliris, project leader for Buro Happold, which is providing structure and MEP services on the project.
The spaces between the screens provide balconies and terraces, meaning the buildings always appear to be alive as people make use of these social spaces.
In addition to recalling the rock strata, the project is also intended to reflect the history and topology of the region, creating a sense of the ancient caves which would have once populated the region.
Implementing such a design required careful selection of materials. Concrete was selected because of its ability to fit the structural demands of the project, but also the construction culture of the region.
Concrete is the customary building material in Jordan and is the material of choice for local builders.
"We recognised the importance of establishing a clear and effective stability diagram for the structure, but also needed to ensure that our design could be properly executed," says Keliris.
The use of a locally preferred material also helps out with the prevailing aesthetic of the design. Just as the Living Wall is embedded into the raw material fabric of Jordan, the accessibility of its construction material means it is also embedded in the cultural and economic fabric of the country.
Jordan is an area frequently affected by seismic activity. Therefore the design and implementation of Living Wall had to be done in such a way so as to withstand frequent earthquakes. "Seismic effects are directly related to weight," says Keliris.
It was critical in Living Wall to reduce the overall mass of the construction.
To assist in this, lightweight floor slabs have been used.
These comprise of simply-reinforced concrete waffle slabs, supported on a two-way grid of reinforced concrete beams.
In addition to reducing the weight, structures need to be able to resist laterally applied loads during an earthquake.
Since the front building comprises five separate towers connected below their lowest half, the "connection" of the towers through the podium is key to establishing the performance of the entire structure.
Because the five towers are connected, the way in which they react to vertical and lateral movement is significantly more complex than that of independent towers.
Mass is evenly distributed across the podium, meaning in an earthquake, the buildings will flex more uniformly, so the sway of one tower should not influence the sway of another.
"Seismic resistance has been further achieved by sub-dividing the podium into smaller building blocks, allowing each block to behave independently of the others, with its own dual lateral stability system of concrete cores and moment frames," explains Keliris.
Ensuring the buildings stay stable required the use of novel design solutions.
Each tower stems from a concrete core which is designed to act in conjunction with the floor beams and columns.
During an earthquake, the beams regulate, and ultimately limit, the seismic activity of the towers, similar to the way in which electricity is regulated through the use of electrical fuses.
"The idea behind the system is that in the event of a severe earthquake, the concrete beams which form the movement-resisting frames act as fuses. They limit the force transferred to the sensitive elements of the structure, just like a fuse limits the electricity running through a plug," says Keliris.
Moreover, concrete plays a significant role in ensuring structural damage can be easily repaired. Because of the design of Living Wall, any affects from seismic activity will first occur within the concrete beams before spreading to the floors.
Because the beams are made from reinforced concrete, repair is relatively simple, since any localised spalling of the concrete can be boxed out and grouted without any major works being necessary.
By creating a structure designed to emulate the rock in which it sits, in a seismic zone, the Living Wall could run the risk of succumbing to the damage caused by earthquakes.
Yet its design and implementation have created a practical solution to sustainable living, while acknowledging the local culture.
The inherent sustainability of the tower design is combined with shaded social spaces below to create a pleasant living environment for residents, and innovative construction using vernacular materials will help Living Wall to continue to breathe life into its rock shelf.
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