Rib

RIB. - This is the name generally given to the arch placed diagonally that forms the load-bearing framework of vaults. This principle was not unknown to the Romans, who, however, applied it only for the purpose of reinforcement and without making the structures project from the surface. The projecting ribs of the Hispano-Moorish domes of the 9th-10th centuries have only a decorative function; attempts at load-bearing arches are instead observed in Armenian churches of the late 10th century and the beginning of the next, but only to the Lombard builders must be acknowledged the merit of introducing this system and of its diffusion.

At the end of the 11th century they were adopted in S. Ambrogio and then in S. Nazaro Maggiore, also in Milan. In Lazio they appear, around 1050, in S. Flaviano at Montefiascone and in the churches of Tarquinia; and in this same century they are also found in France and in England (the cathedrals of Durham and Peterborough).

In France ribs transverse to the nave were also used, particularly frequent in Normandy and Burgundy, and in the late Gothic there were, also in England and Germany and Spain, stellar vaults, that is, with ribs intersecting in various directions. In late Gothic the ribs are often simple decorative elements.

In Italy, on the other hand, the ribs retain the original arrangement of diagonal arches still in the full fifteenth century (S. Agostino in Rome, S. Maria delle Grazie in Milan), except in Sicily and Sardinia where the influence of Aragonese Gothic is manifest.

In the apses the ribs almost always have only a decorative value; in the domes, on the other hand, the static function of the ribs has assumed decisive importance, constituting the load-bearing system of the entire architectural organism (the greatest examples in S. Maria del Fiore, where the ribs made it possible to eliminate the centering, and in the Vatican basilica).

In the seventeenth century Guarini also adopted intersecting ribs in domes, achieving constructive daring (S. Lorenzo in Turin) surpassed only in the last century by Antonelli in S. Gaudenzio in Novara.

The section of the ribs, at first rectangular, was later complicated with moldings to the point of also taking on a decorative character. As material, cut stone was mostly used, but in Emilia also brick and terracotta in general.

Mario Zocca