ROBOT.LK

EIGHT centuries on, the flying buttresses of Bourges Cathedral in France still beguile engineers. The secrets behind this marvel of medieval masonry are now about to be laid bare, thanks to a group of researchers who are rebuilding it, brick by brick.

Using a laser scan of the cathedral, a team led by John Ochsendorf of the Massachusetts Institute of Technology have 3D-printed thousands of bricks and are building an exact 1:50 replica. The researchers hope to use the mock-up to devise a way to gauge the stability, and thus safety, of historical buildings built of brick and stone.

Modern buildings are usually constructed around a steel framework. The steel pieces are fused, so under stress from a sinking foundation or an earthquake, say, the framework behaves as a cohesive unit.

Masonry structures are much more complex. Removing a single brick can change the pattern of stresses throughout the building. This makes it difficult to capture the forces at play, says Mathew Bronski, a structural engineer at architecture firm SGH in Boston. Computer models and simulations help, but there are a lot of inherent shortcomings, he says.

"People have been drawing buildings forever, but they've often been making up the building as they go because they can't measure it," says team member John Tallon at Vassar College in Poughkeepsie, New York. "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."

Building the replica is painstaking work, but Ochsendorf thinks the process itself may be as valuable as the mechanics uncovered. For students of architecture and structural engineering, hands-on experience has largely given way to computer modelling. Techniques like 3D printing could be a way of reconnecting them with the craft behind the science, he says.

"Until now [structural engineering] has been dimensionless," says Ochsendorf. "'Here's a prototypical dome of this thickness and this span' – but it wasn't modelled off of any specific building." As 3D printing becomes ubiquitous, he says, learning could become less abstract and students will increasingly work from real-world examples.

This article appeared in print under the headline "History comes alive in 3D-printed bricks"