A team of researchers at the Massachusetts Institute of Technology has painstakingly scanned the entire Bourges Cathedral in France. The reason? The construction of a 3D printed replica could help to reveal the structural secrets of ancient buildings.
The team is led by John Ochsendorf, an engineer who specialises the structural safety of historic monuments and the design of more sustainable infrastructure. An expert on the mechanics and behaviour of masonry structures, Ochsendorf has been collaborating with art historians, architects and engineers to investigate how the construction of 21st-century buildings might benefit from the lessons learned from medieval practitioners.
Speaking to New Scientist magazine, Ochsendorf said 3D printing will act as a complement to computer modelling to help connect students to the craft buried beneath the science; assist in determining the stability and safety of historic buildings, as well as enable the transference and application of such knowledge into modern buildings.
"Structural engineering has been 'dimensionless,'" Ochsendorf said. "It wasn't modelled off of any specific building."
3D printing, he added, will help students learn from tactile examples and remove a layer of abstraction from the process of understanding how buildings are actually constructed.
Built in the 12th century, the Bourges cathedral is one of the earliest examples of the use flying buttresses, intended to fortify the structure of the building. The flying buttress is a masonry arch extending off the outside of a building, often along the length of the nave of a cathedral, which transfers the thrust of the roof outwards and down to a pier.
This innovation allowed for the creation of the great soaring, light-filled, Gothic cathedrals of medieval Europe. As this was a fairly new technique when the Bourges Cathedral was designed, the walls of the building were still built to a substantial thickness.
The structural integrity of this brick building depends on a family of bricks working together.
“What happens to one brick can affect the stress throughout the entire building so that it’s even more complicated to understand how such buildings might behave in response to physical forces,” said Mathew Bronski, a structural engineer at architecture firm SGH in Boston.
By scanning and 3D printing thousands of bricks to create the Bourges replica at 1:50 scale, the team can see how those bricks might behave under environmental pressures.
Team member Andrew Tallon, a professor of architecture at Vassar College, added that while computer simulation and modelling offers some insight into the inner workings of masonry structures, they lack the critical details needed by architects and designers to further their understanding.
"People have been drawing buildings forever, but they've often been making up the building as they go because they can't measure it," Tallon told New Scientist. "With a laser, you can get into places that you couldn't hope to reach without three months of scaffolding and shutting down the cathedral you're working on."