How Antoni Gaudí modeled the Sagrada Família and calculated its structure
Gaudi loved the catenary arch and used models of string and small bags of sand to calculate how load would be transferred from ceiling to ground. The string represents the line of force running through walls, arches and beams. The bags of sand represent point loads, abstractions of the weight of the building itself.
[These photos were taken in Gaudi’s workshop turned museum in the basement of the Sagrada Familia, during a tour of the church in 2009.] The string and sand represent an inversion of the forces that will act on the built structure, so Gaudi used mirrors to reflect the model, and traced the curvature of the strings to determine how the arches needed to be built.