Groin vault
Introduction
The groin vault is the vaulted architectural element that is used to cover quadrangular spaces; It results from the intersection of two barrel vaults, which intersect perpendicularly. Geometrically, it is generated by two orthogonal semi-cylindrical surfaces whose lines of intersection, or edges "Edge (architecture)"), are ellipse arcs that intersect at the upper vertex.
Its use is not only widespread due to its easy construction with formwork, but also because it allows the forces of the roofs to be distributed towards the exterior walls with great ease.
History
Ancient Rome
Roman engineers and architects spread it throughout the Empire, using it as an alternative to lintel systems and flat roofs for small spaces. In important installations, Roman baths were often covered with enormous groin vaults, such as the Baths of Diocletian in Rome, built between 298 and 305, the Baths of Caracalla, also in Rome, from the beginning of the century with a groin structure 32.9 meters high[1] or the Baths of Cluny in Paris. Other examples located in Rome itself would be Trajan's market or the Basilica of Maxentius.
The ashlar groin vault poses problems of stereotomy, which the Romans used to avoid by staggering the falsework so that the base of one was at a higher level than the key "Key (architecture)") of the other.[2] Of the few groin vaults from Roman times that remain, several belong to the Eastern school.
There is an example of a carved stone cross vault in the access gallery of the southern theater of Gerasa (Jordan), 2nd century. Gerasa, although part of the Roman Empire, remained deeply influenced by Greek traditions. All buildings have the particularity of being built in medium or large "Survey (construction)"), with a tight joint "Survey (construction)"). The mortar that was sometimes used as a coating was never used there as a binder for masonry and no evidence has been found in opus caementicium.[3].
The triumphal arch of Cáparra in Extremadura (Spain), dating from the late 19th century, is another notable Roman example. The only surviving monument on the Italian peninsula that has a well-matched cross vault in carved stone is the mausoleum of Theodoric, the Ostrogoth king, built in Ravenna in 530. The 'zigzag' way of assembling the voussoirs on the façade, although practiced in the Roman Empire during the imperial era, only seems to be practiced in the Middle East in the century, leading to the hypothesis of that the creator of the mausoleum could have come from Syria or Asia Minor.[4].