External reinforcement

This signifier encompasses the cases in which tensioned elements collaborate with the compression resistant voussoir in order to create a mixed structural performance. An early example is the application of outer steel tie rods to prevent the opening of abutments of the dome of Vasari’s Santuario dell’Umiltà. This solution, although of a retrofitting nature, “does not belong to rehabilitation only but in that matter which turns a concept into a design” (Foraboschi, 2016, p. 971) as it was designed and applied during the final stages of construction. Tension resistance may also be used from the first design stage to overcome lack of weight or support of voussoirs such as in the Grand Théâtre of Bordeaux (R. Etlin, 2015), Periscope (McGee et al., 2013), or Hypar Gate (Fallacara and Barberio, 2018b). Metal is also used to hold voussoirs in place while building a stereotomic structure: in the RFoSAD (Ariza et al., 2017) the stone voussoirs are actually hold in place by cast in place dowel joints, revealing an interesting case of compression and tension working together.