Case study: 360km steel tubes create Saudi Aramco cultural centre's façade
Details have been revealed of King Abzulaziz Center for World Culture's façade, which comprises 70,000 steel tubes that were tested and installed using a customised C#-language programme
Saudi Arabia’s King Abdulaziz Center for World Culture (KACWC) has been fitted with a façade comprising 360km of steel tubes.
KACWC has been established in Dhahran by Saudi Aramco to promote the kingdom’s knowledge economy, in line with the country’s Vision 2030 vision.
Aramco says the center has been built “near the Prosperity Well, the kingdom’s first commercial oil well”.
Custodian of the Two Holy Mosques King Salman inaugurated the centre, commonly known as Ithra, in December 2016 to mark Saudi Aramco’s 75th anniversary.
Details of the project’s façade have now been revealed by Seele, a German firm specialised in the design and construction of façades and building envelopes made from glass, steel, aluminium, membranes, and other materials.
Seele said the project required its team to not only develop “a solution for the construction” operations, “but also the software for the self-learning machines” that were used for each steel element within the façade.
KACWC’s five buildings were designed by its architect, Snøhetta, to “shine in the sunlight like bright pebbles”.
To achieve the vision, Seele created a building envelope as a free-form surface, using thousands of stainless steel tubes bent in three dimensions, to cover a total area of 30,260m2.
The tallest of the three-dimensional, free-form shapes rises 90m, and all the tubes are fixed to a supporting structure made from a weatherproof, unitised building envelope clad with sheet metal joined by standing seams.
The tubes are attached to pins that compensate for the different movements of the building envelope and the tubes.
Approximately 70,000 stainless steel tubes have been used for the project, which, laid end to end, would total 360km.
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The reference point for the geometry, design, production, dimensional checks, and erection of each tube was its virtual centre-line. The distance between adjacent, double-curvature tubes is exactly 10mm.
Each tube had to be marked and bent corresponding to its subsequent position on the structure, and for the sunshades around the windows, some had to be crimped as well.
Visual ‘transitions’ were necessary where the round tube took on the so-called ‘squashed’ look, and Seele said its engineers’ expertise was required to achieve “this geometrically challenging building envelope”.
A façade using stainless steel tubes across all floors had never been built before, requiring Seele to implement numerous tests for the project, as well as special programming for the bending and measuring of the tubes, on free-form bending machines.
Next page: Testing and installation of the 360km-steel tube façade
Testing and installation
Seele says four tests were required to produce a single correctly bent tube. To ensure that the thousands of tubes would be produced efficiently, Seele wrote programmes in the C# computer language to bend and measure machines that can communicate and learn from each other.
Mistakes during production could therefore be reduced to less than 3%, and wastage was also minimised.
Stefan Kloker, senior structural engineer at Seele, explains the process: “With the help of the programming and then collecting the data in a database, we were able to build a mock-up and get the self-learning machines up and running within four months.
“The solution was to back-calculate the final geometry of the bent tube to a straight tube prior to bending, simulate the bending process, check the accuracy of fit, and then produce the tube after checking all the data.
“As every specific data record is stored, it can be reconstructed at any time.”
The Seele team was therefore able to account for critical design factors – such as tight tolerances, material behaviour, the fitted tubes’ accuracy, and the tubes’ fixing to the supporting structure – during production.
Owing to the material’s properties, there was only one chance per tube to get the bending and twist right, because re-bending in the machine was impossible. Bending the tubes beyond their required shape accounted for the springback of the steel.
Seele engineers also had to account for the markings and the drilling for the fixings, so that the positions would be obvious after bending, and the drilled holes would be in the right places.
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The bending machines developed new algorithms automatically through a measuring system, which were then used as the basis for performing each bending process.
Each tube was bent, with its ends tapered for connection, using the bending and measuring machines, and based on precisely generated 3D data. The exact erection sequence was also specified through computer simulations.
While each tube is a “one-off” piece, Seele says each element was categorised according to its connections, in order to reduce the complexity of the parts.
As a result, every tube required individual instructions in the form of precise QR codes and laser engraving, which was automatically applied to each tube.
After production, every tube was wrapped separately by Seele to protect the surfaces, and then packed in crates to match the erection sequence on site. The crates were delivered to the site in a fixed order.
Site crews scanned QR codes to identify the tubes and their position on the building by way of a 3D model.
Jürgen Laky, managing director of Seele Middle East, outlines the benefits of using technology for KACWC: “All phases of the project – from design through production to erection – benefited from the use of a coherent system throughout.
"Erection procedures on site in the desert of Saudi Arabia were distinguished by efficiency and economy.
“As a result of the perfectly planned logistics and ingenious preparations, not one of the tubes was wrong or missing when work was carried out on site.”
Seele says its work on the project has ensured that the façade “wraps itself around the building without any steps or edges, has harmonious, rounded features, and tubes that run perfectly parallel”.