Some Notes on Gothic Building Processes: the Expertises of Segovia Cathedral.

Gothic architecture has aroused the interest of architects, engineers and historians for centuries (Frank1 1960). The technical point of view has also received attention; in particular, there is an abundant literature on gothic vault construction and structural behaviour. The rational approach of Viollet-le-Duc (1854), followed by Choisy (1899) and many others, was subsequently criticized, mainly by Pol Abraham in the 1930s (for an excellent risumi of the debate, see Kubler 1944, pp. 135-7; see also Mark, 1977). From a structural point of view the discussion focused on the actual functioning of the different elements of the vault (the ribs, webs and bosses) and the debate was actually closed by Heyman (1 966, 1968) with the application of the ideas of modern limit analysis to masonry structures. However, the deep meaning and the practical consequences of Heyman's disco~reries have not yet been fully understood by many architects and engineers, who are still using sophisticated computer programs to try and obtain the actual state of internal stresses in niasonry. There is another aspect that has been rarely considered: the cathedral must also have been in equilibrium during the building process. In any of the intermediates phases, the sequence of the operations, the dispositions of scaffoldings, materials, etc., must have assured a safe state o