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The second vault that I wanted show you is a vault existing in the cloister of the Segovia cathedral, built at the end of the 15th. century by one of the most important gothic architects in Spain, Juan Guas. As you can see the vault shows one interesting drawing of ribs, the diagonal arches, the tiercerons and formerets compose an interesting and intelligent crossing up of nervatures (photo 1).
In this case we took measures of the real vault with which we obtained an accomplished design of the vault, in plan and elevation. That allows us to notice how, apparently, the three main arches with which the vault is built seemed to be different. The diagonal arch was a semicircular arch whit its centre, set in the impost level, the tiercerons reach the height 3 and the formerts reach the height 4, so that the three arches, as in the previous vault, seem to have different curvatures (photo 2).
But one most accurate observation of the cluster of ribs in its springs allows us to notice different inclinations of the nervatures, and that idea suggests to us that perhaps the vault could be built with only one arch. If we use the semicircular diagonal arch and we lightly tilt it around its beginning point in the impost level till it reaches the height 3, the tierceron could be the same arch as the diagonal one. Once again it should be possible to tilt the same arch forward a little bit more till reach the height 4 and in this case the former also should have the same curvature, so that all of the vault could be built with only one arch (photo 3,4). [....]
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