Taking on the towers
Antoni Gaudí’s La Sagrada Familia church, in Barcelona, is finally due for completion in 2026, one hundred years after his death. Gaudí’s expressive and flowing vision has been an adventure in structural design and construction technology ever since he started work on the project in 1883.
In 2014, with the building 60% complete, the Sagrada Familia Foundation approached Arup to help with the remaining structural design, particularly how to produce the remaining six towers, dedicated to the Four Evangelists, The Mother of God (Mare de Deu) and Jesus Christ.
6 new towers designed in prestressed stone
172.5mwill be the height of the central Jesus Tower when complete
40%of the project will be completed between 2016 and 2026
The team were aware that towers built in traditional masonry or earthquake resistant reinforced concrete (with stone cladding) would make the towers too heavy for the foundations and crypt below. Instead we developed a scheme using the stone itself as structure, producing a beautiful finish and reducing the weight of the tower by a factor of two. This approach also reduced build cost and accelerated the construction programme.
Jordi Faulí, Architectural Director at the Sagrada Familia Foundation commented "The work of the Arup team has allowed us to build the central towers with the innovative technique of pre-stessed stone. We value their rigour and the research for the most effective, clear and simple solutions."
The resulting design used pre-stressed stone masonry panels as the primary structural element. Pre-stressing provides greater strength to the panels, allowing them to be accurately fabricated remotely, transported to site and easily assembled on site by crane. This solution also allows the panels to resist stresses imposed by wind and earthquakes.
Arup modelled each and every component in 3D to a construction level of detail (including nuts, bar threads, couplers, fillets and chamfers). Carefully designed connections ensure that when panels are craned into place, they fit together like Lego blocks, without further adjustment.
Our pre-stressed stone panel method echoes the pure masonry construction used in the earlier construction of Sagrada, while the more modern off-site manufacture approach guarantees consistently high quality. Installing a 5m tall by 4m wide panel now take 30 minutes, saving time and enabling a safer construction process – important as the basilica will remain open during the final years of the build.
Human, digital, physical
In all our work on the Sagrada Familia we have used a new generation of digital tools to produce workable structural designs. This parametric approach combines deep human knowledge of the structural variables in the Towers’ form and position, with powerful algorithmic tools that could model the hundreds of subtle variations of geometries for the design. This human-plus-digital ethos was the best way to make Gaudí’s design pragmatic to construct in a realistic timeframe, and would have been unrealistically laborious to carry out without cutting-edge technology.
Our experience working alongside 2BMFG Architects and the Sagrada Familia Foundation has demonstrated how the near-limitless capacity of digital tools, used creatively by human beings with their experience and insight, can solve almost any engineering challenge – even on projects as singular as Gaudí’s church. Design of the towers is now complete and construction of the tower dedicated to The Mother of God had reached the ninth level by February 2017.
This digital model is then used to automatically cut the individual blocks of stone that are accurately fabricated into a panel using laser cut plywood templates; pre-stressed with machined stainless steel bars; and assembled on site.
Watch the video below from La Sagrada Familia Foundation to discover more about how the central towers are being raised:
The next chapter
We are now helping the Sagrada Familia team with the design of nucleus, stair and lift within the Jesus Christ tower, the roofs for the Nave and the pinnacles that will complete the tops of the towers for this breath-taking church.