Monday, April 6, 2015

Flying Carpets – Foster’s Concrete Canopies

A good while back I had the great opportunity to visit the Kingdom of Jordan and  dear friends of mine.
Beyond visiting the out of this world amazing Petra, a few Biblical sites, beduin and desert castles  – well, the Concretely highlight was the new international airport to Ammann. Queen Alia International Airport designed by Sir Norman Foster and finished in 2013.

A nice opportunity to search into the construction of the airport came when asked to lecture about concrete as an architectural material at the Royal Danish Academy of Fine Arts, School of Architecture.

[Great light, grand spaces, and nice temperature - but was this really prefab or cast on site? Image by Yours Concretely]

[The modular design of tessellated roof canopies allows for a planned expansion of the airport, canopy by canopy. Image via]
[Detail of the column head. Really tight and great surfaces. Image by Yours Concretely]
[The large outdoor area - in the poor image taken with my mobile phone, the tessellated canopies appear to continue. Image by Yours Concretely]
[Images of Queen Alia Intl Airport. Photos by Anne-Mette Manelius, Yours Concretely]

Cast in place or prefab elements?
The search was initiated from my wonder - how were the gigantic canopy-like vaulted ceilings actually made? It was puzzling because the structure appeared, at the same time, to be cast in place and cast as prefabricated concrete elements. The details and connections as well as the finish of the concrete is of much higher quality than anything else I had seen in Jordan. – furthermore,  there are clearly defined connections between structural elements. All indicating the use of prefabricated concrete.

Structurally, on the other hand, such large-spanning vaults are traditionally constructed as cast in place. Also – were these huge structure made from elements, - the cranes and trucks to deliver them would have had to be enormous. Furthermore, the price of human labor – a crucial ingredient in concrete, Adrian Forty reminds us – would be fairly low in Jordan.

A visit to the airport’s Wikipedia-page added weight to my ponder as it stated how the airport is composed of 127 concrete domes, each weighing up to 600 metric tonnes

[Detail of the ceiling with acoustic elements mounted on the concrete - oh concrete bliss. Photo by Yours Concretely]

Cast in place AND as prefab
The beauty of concrete is that it comes in many forms and properties - and the revelation is that the structure is cast as prefab as well as cast on sight. High performance fiber-reinforced concrete (HPC) was used to make the  stay-in-place formwork elements. They were thin double-curved concrete shells cast in molds made in a factory in Greece. Here shipbuilding skills were used to develop the curves.

The challenge for these elements comes down to this: at the end, the hardened concrete structure of each canopy will function as one. Yet the most challenging loads impact the elements during construction as well as transportation from abroad. The construction of the airport using prefabricated concrete molds was possible with the development of high performance concrete.

[Images from the engineering of the high performance fiber-reinforced (HPC) concrete shells. Images above are via Greek consultants Cubus Hellas]

Behind the scenes
I enjoy the construction of architecture, so I always enjoy the process more than the final result. With impressive works such as this one, I want to see the "making of" images. The British Concrete Quarterly ran a nice article on the project with lots of facts that you can open here – yet no images from construction. Below is a collection of images that I have found on web sites of contributors
to the project.
[Image of Queen Alia Airport under construction. Via 'High Contrast' Wikimedia]

[Montage of hollow fibre-reinforced concrete elements. Via Joannou & Paraskevaides]
[Images from the engineering of the high performance fiber-reinforced (HPC) concrete shells. Image via Greek consultants Cubus Hellas]

Project: Queen Alia International New Airport (2005-2012)
Client: The Hashemite Kingdom of Jordan Ministry of Transport 
Architect: Foster + Partners
Structural and MEP engineer: Buro Happold
Contractor: Joannou & Paraskevaides