Structural typology

Arches can be based on two structural principles:

It is possible that these structures will be combined in mixed works. An example of them is the so-called "aqueduct II" of Almuñécar. It consists of a Segovia-type arch that in the highest openings - the three central ones - are reinforced with supporting arches that rest on pilasters attached to the main pillars.

The behavior of both types when faced with collapses is very different. In the "Segovia type" the breakage of an arch can cause significant damage to the entire work. In the "Mérida type", on the other hand, the breakage of one or more arches can weaken the whole, but the pillars remain intact long enough to make necessary repairs possible (and even to survive the centuries).

Construction techniques: rigging

The construction techniques of the arches are varied. For works in which a prestigious image of Roman power is pursued, stone ashlar (opus quadratum) is used, but the most common is the use of easier and cheaper construction techniques. Local materials are usually used, the transportation of which is not too expensive. The application of concrete (opus caementicium) facilitated the massive dissemination of this type of works. To protect the concrete, it is covered with masonry (opus incertum), brick (opus testaceum) or ashlar facings. Although it is possible to find arches built entirely of masonry, the same is not true of brick, which only appears as a covering for the concrete.

The construction technique for coated concrete consists of first raising the exterior walls in bands or courses. Then the space left between them is filled with layers of lime and sand cement in which irregular pieces of stone are embedded (caementa).

There are mixed techniques: in the Pont du Gard, which is part of the aqueduct that supplied Nemausus, today Nimes, in France, the entire structure is made of ashlar, except for the canal, which is made of masonry. In the arch of Los Milagros, in Mérida "Mérida (Spain)"), groups of five courses of granite ashlars alternate in the covering of the concrete core of the pillars with others composed of the same number of courses of red brick. The brick grouting gives the work an interesting chromatic effect, apart from the practical usefulness of leveling the work periodically. The arches that support the pillars are also made of brick, except for the one located over the dry channel of the Albarregas River "Río Albarregas (Spain)"), over whose valley the arches fly. The latter is made of carefully carved granite voussoirs.

An alternative solution for arches

In the area known as Los Bañales, in the district of Uncastillo (Zaragoza, Spain), an alignment of 32 pillars is preserved today (in ancient times there had to be just over 70),[4]​ built in roughly hewn stone ashlars that follow one another at fixed intervals of four meters. At no time did they hold any bow. They were part of a convoy whose destination is not well known. The upper ashlar of each pillar has a notch that served as support for the channel. The third or fourth ashlar from above has a groove that closes with the immediate ashlar, so that the pillar is pierced. There is no other possibility, except that the channel was made of wood and that the holes drilled in the pillars were used to launch props that acted as tie rods. The wooden channels for the conduction of water are attested by Faventino in his work De diuersis fabricis architectonicae, from the 1st century, although, in this case, the presence of legionary marks on the aqueduct allows us to assume that it was a work carried out in the last years of the century BC. C. with the help of the Macedonian Legio IV.[5]​.

Structural typology

Arches can be based on two structural principles:

It is possible that these structures will be combined in mixed works. An example of them is the so-called "aqueduct II" of Almuñécar. It consists of a Segovia-type arch that in the highest openings - the three central ones - are reinforced with supporting arches that rest on pilasters attached to the main pillars.

The behavior of both types when faced with collapses is very different. In the "Segovia type" the breakage of an arch can cause significant damage to the entire work. In the "Mérida type", on the other hand, the breakage of one or more arches can weaken the whole, but the pillars remain intact long enough to make necessary repairs possible (and even to survive the centuries).

Construction techniques: rigging

The construction techniques of the arches are varied. For works in which a prestigious image of Roman power is pursued, stone ashlar (opus quadratum) is used, but the most common is the use of easier and cheaper construction techniques. Local materials are usually used, the transportation of which is not too expensive. The application of concrete (opus caementicium) facilitated the massive dissemination of this type of works. To protect the concrete, it is covered with masonry (opus incertum), brick (opus testaceum) or ashlar facings. Although it is possible to find arches built entirely of masonry, the same is not true of brick, which only appears as a covering for the concrete.

The construction technique for coated concrete consists of first raising the exterior walls in bands or courses. Then the space left between them is filled with layers of lime and sand cement in which irregular pieces of stone are embedded (caementa).

There are mixed techniques: in the Pont du Gard, which is part of the aqueduct that supplied Nemausus, today Nimes, in France, the entire structure is made of ashlar, except for the canal, which is made of masonry. In the arch of Los Milagros, in Mérida "Mérida (Spain)"), groups of five courses of granite ashlars alternate in the covering of the concrete core of the pillars with others composed of the same number of courses of red brick. The brick grouting gives the work an interesting chromatic effect, apart from the practical usefulness of leveling the work periodically. The arches that support the pillars are also made of brick, except for the one located over the dry channel of the Albarregas River "Río Albarregas (Spain)"), over whose valley the arches fly. The latter is made of carefully carved granite voussoirs.

An alternative solution for arches

In the area known as Los Bañales, in the district of Uncastillo (Zaragoza, Spain), an alignment of 32 pillars is preserved today (in ancient times there had to be just over 70),[4]​ built in roughly hewn stone ashlars that follow one another at fixed intervals of four meters. At no time did they hold any bow. They were part of a convoy whose destination is not well known. The upper ashlar of each pillar has a notch that served as support for the channel. The third or fourth ashlar from above has a groove that closes with the immediate ashlar, so that the pillar is pierced. There is no other possibility, except that the channel was made of wood and that the holes drilled in the pillars were used to launch props that acted as tie rods. The wooden channels for the conduction of water are attested by Faventino in his work De diuersis fabricis architectonicae, from the 1st century, although, in this case, the presence of legionary marks on the aqueduct allows us to assume that it was a work carried out in the last years of the century BC. C. with the help of the Macedonian Legio IV.[5]​.