Although they have existed for centuries and even millennia, stone and masonry bridges are still virtually unknown to engineers. In the 21st century, when it seems that the methods of analysis and calculation are been deeply studied, it is not yet possible to assess with sufficient guarantees what are the acceptable thresholds of movements in vaults, walls or piles in the face of foundation problems (the Achilles heel of these structures), or the fillings contribution and spandrel walls capacity, and other significant uncertainties.
Although very important steps have been taken for the engineering study, not only historical, of stone and masonry bridges, it has been found that it is still necessary to deepen the knowledge of the configuration of these bridges of their various components and of the design and construction methods.
This research aims to shed light on the lack of knowledge that still exists, pursuing the following objectives: offering a glossary of terms, with the corresponding explanations, that will help nowadays engineers to understand the jargon of those treaties; to document the auxiliary structures (for the construction of foundations, frameworks for vaults and access gateways); to study and systematize the maintenance works; to document the criteria related to roadways, capstones, belt course, stoves, parapets and, finally, to define the project criteria and the construction methods corresponding to all the components of the bridges: plinths, piles, walls, spandrel walls, vaults, fill materials, drainage, etc.
Due to the breadth of the topic, the work carried out will have a limiting geographical scope and focus on the study of the Spanish treatises on the construction of stone or masonry bridges between the 16th and early 20th centuries.
These treatises, in chronological order, are: the Veinte y un libros de los Yngenios, and Maquinas de Iuanelo, which deal with a multitude of hydraulic themes, including bridges; the work of Fray Lorenzo de San Nicolás, Art and Use of Architecture; the treatise on bridges that Fray Antonio de San José (Padre Pontones) wrote between 1759 and 1768; and, finally, the contribution of the military engineer Miguel Sánchez Taramas completing the A Treatise containing the elementary part of fortification (1746) by John Muller.