L’Abbatiale est le seul vestige visible d’une ancienne Abbaye bénédictine fondée au IXe siècle. Elle a été en grande partie construite entre le XIe et le XIIe siècle. Cet ensemble architectural est remarquable par sa grandeur et la richesse de son histoire.

L’Abbaye de Cruas fut fondée par des moines bénédictins autour de l’an 804, en pleine période carolingienne. Elle fut un lieu de prière, d’étude et de travail pour les moines. Au Moyen Âge, elle bénéficiait d’une grande influence et possédait de vastes terres dans la région.

Comme dans la plupart des monastères bénédictins, la vie des moines à l’Abbaye de Cruas était régie par la règle de saint Benoît, qui mettait l’accent sur la prière, le travail manuel et l’étude. Les moines se consacraient à la prière divine (les offices liturgiques), mais également à la gestion de terres agricoles, à l’artisanat et à l’éducation. Ils étaient responsables de la culture des terres, de la production de vin, de l’élevage et d’autres activités économiques, garantissant ainsi l’autosuffisance du monastère.

La vie monastique était marquée par une grande rigueur, avec des périodes de silence, des prières régulières et une discipline stricte. Le monastère servait également de centre d’hospitalité pour les pèlerins et de lieu d’enseignement pour les jeunes moines en formation.

L’Abbatiale de Cruas est particulièrement célèbre pour sa rare et très bien conservée tribune monastique, qui est un des éléments les plus spectaculaires de l’édifice (elle n’a pas été restaurée, mais seulement dégagée de son carcan d’alluvions amenés par les débordements réguliers du ruisseau Crûle, situé au Nord). Cette tribune, construite au milieu du XIIe siècle, est un espace surélevé destiné à accueillir les moines pendant les offices. Elle permettait aux moines de suivre les chants liturgiques et les prières tout en étant séparés de l’assemblée des laïcs.

L’Abbatiale de Cruas est aussi remarquable pour ses chapiteaux sculptés, particulièrement ceux de la tribune monastique et de la crypte. Ces chapiteaux, pour la grande majorité, œuvres de tailleurs de pierres locaux, présentent des motifs décoratifs très variés.

La crypte, bien préservée, constitue l’un des éléments les plus anciens de l’abbaye. Elle servait à abriter les reliques sacrées et à fournir un espace de prière supplémentaire. La crypte a une atmosphère particulière, étant un lieu de recueillement et de méditation qui préserve une grande part de l’histoire spirituelle du site. L’architecture de la crypte est sobre mais impressionnante, avec sa multitude de colonnes hétérogènes et ses voûtes d’arêtes qui créent un espace intime et mystique.

Entre autres trésors, l’église possède encore son Maître Autel du XIe siècle (une belle pièce en marbre) consacré en 1095 par le Pape Urbain II lors de son déplacement l’amenant à Clermont pour prêcher la première croisade et une magnifique mosaïque du début du XIIe siècle qui représente le prophète Elie et le Patriarche Hénoc sous la main de dieu (ce sont les deux seuls hommes, selon l’ancien testament,  à avoir été enlevés vivants au ciel). Encadrée par ces deux personnages, nous avons une représentation du jardin d’Eden, avec l’arbre de vie et l’arbre de la connaissance du bien et du mal.

Le déclin de l’Abbaye débute à la fin du Moyen Âge, et elle subit de nombreuses destructions, notamment pendant la guerre de cent ans (1337-1452) et les guerres de religions (deuxième moitié du XVIe siècle). Les moines sont chassés de l’Abbaye de plaine et les bâtiments conventuels sont partiellement ruinés.

Au début du XVIème siècle, avant de fuir les crues causées par Crûle pour aller s’abriter sur les hauteurs, les moines, par manque de moyens, ont muré la tribune monastique, le reste de l’Abbatiale n’a pas été protégé. Par la suite, l’eau a charrié toutes sortes de boue et de vase, ce qui entraîna peu à peu le comblement des parties non murées. Les moines revenant de temps en temps dans l’Abbatiale, n’eurent pas d’autres options que de combler par des apports de terres volontaires et de la chaux (pour assainir les sols) le reste de la nef et les bas-côtés. Ces opérations se répétèrent jusqu’à ce que le niveau du sol soit homogène dans tout l’édifice. En plongeant ainsi dans l’oubli la tribune basse, ils ont donc créé une nouvelle église de plain-pied.

On peut encore aujourd’hui voir les traces sombres laissées sur les piliers, nous signalant l’ancien niveau du sol.

Protégé et entouré par ses quatre murs, le niveau inférieur de la tribune a ainsi longtemps été perçu comme étant une seconde crypte.

Les fouilles archéologiques entreprises à partir des années 1970 ont permis de mettre en lumière de nombreux aspects de l’histoire de l’Abbatiale et de l’abbaye de Cruas. Ces fouilles ont révélé des vestiges importants, notamment ceux d’une Domus gallo-romaine, les fondations d’un édifice paléochrétien de la fin du Ve ou du début du VIe siècle, des parties de la première Abbatiale élevée au IXe siècle, des tombes, des objets liturgiques et des pièces de monnaie entre autres. Elles ont également permis de mieux comprendre l’organisation de la vie monastique au Moyen-Âge et d’identifier les différentes phases de construction et de transformation de l’abbaye au fil des siècles.

Lors des fouilles archéologiques, environ 1 200 mètres cubes de déblais ont été enlevés, ce qui a permis de redécouvrir la tribune monastique et d’autres éléments architecturaux enfouis sous les couches de sédiments accumulées au fil des siècles. Les fouilles ont aussi mis en évidence l’importance de l’abbaye dans la région à travers les siècles.

L’abbatiale de Cruas est donc un lieu chargé d’histoire et de spiritualité, un témoignage impressionnant de l’architecture religieuse du Moyen Âge et de la vie monastique. Avec ses chapiteaux sculptés, sa crypte préservée, son authentique tribune monastique et les fouilles archéologiques qui ont révélé son passé, elle continue d’être un lieu de mémoire et de découverte pour les visiteurs. Elle est un exemple de la richesse historique de l’architecture romane et un symbole de la vie monastique dans l’ancien Vivarais

Between 1825 and 1850, more than 450 major suspension bridges were built in France.

If a small part of them remained faithful to the Anglo-Saxon chains, the vast majority was based on wire cable suspension, Seguin’s invention.

The latter and their associates probably built between 80 and 90 of them.

From France, the technique of the light cable suspension bridge spread to Switzerland, Italy, southern Germany, Spain, etc.

However, a terrible accident in Angers in 1850 caused more than 200 victims: a regiment passing in close ranks as a storm broke out.

The combination of the soldiers’ footsteps and the gusts of wind caused the structure to oscillate uncontrollably, which suddenly collapsed.

This was a phenomenon that was poorly understood at the time: resonance. This discredited on this type of work, particularly in Europe, giving way to a new architecture of bridges made of arches and metal beams, then concrete structures.

However, their construction continues and develops in the United States, based on the model of suspension by fine steel wire cable, while introducing the more rigid metal deck.

The suspension bridge provides an unrivaled solution for crossing large spans.

The Brooklyn Bridge in New York (1883) and the Golden Gate Bridge in California (1937) achieved legendary fame.

The history of the suspension bridges between Tournon and Tain is rich.

Marc Seguin himself led the construction of three of them. The first is the historic bridge completed in August 1825.

Its traffic was immediately very important but it suffered from two important limitations: it was too low for the development of steam navigation and it was too narrow with a single passageway.

In 1848, the Seguins received a state subsidy to demolish it and replace it with a new structure, higher and with two tracks.

To avoid interrupting traffic, the new bridge was built slightly downstream in 1848-49.

This is the current Seguin footbridge, preserved essentially in its original state. The demolition of the historic bridge followed.

However, Marc requires that the masonry bases be preserved to build a small raised footbridge in memory of the historic work.

This third Seguin work was completed in 1850. It has often been confused with the 1825 bridge of which it only retains the masonry bases.

The success of the Tournon-Tain bridge triggered a mania for suspended structures, particularly in the current Rhône-Alpes region.

Projects are flourished in Lyon sur la Saône, Grenoble sur le Drac, in the department of Ardèche, in Ain, etc.

Among the very first works carried out entirely using the Seguin technique, with cables, are the bridges of Thévenet, an architect from Tournon who was the Seguin site manager for the 1825 bridge.

He then directed the construction of Andance – Andancette on the Rhône and the Doux bridge at Tournon – Saint-Jean (today replaced by a concrete structure).

They were both put out to tender in 1827 and immediately set about opening the following year. With the Fourques bridge (Bouches-du-Rhône) on the Petit Rhône, the Andance-Andancette structure is today the most faithful witness to the general architecture of the first Seguin style suspension bridges, the porticos of entrance in particular.

The suspension bridge was successfully tested by the ‘Ponts et Chaussées’ administration at the end of August 1825, after static load tests and then the passage of heavily loaded convoys.

It was inaugurated and opened for the first time to the public on August 25, 1825, on the occasion of the “Onion Fair”, a Tournon fair of medieval origin which then lasted three days! It was a considerable popular success: the Seguin brothers were celebrated in both cities for a whole week: cannon shots, blessing by the bishop, banquet on the bridge, popular balls, parades, aubades, songs, etc.

Marc Seguin, who was already known in the region as an engineer, then became a popular figure of national stature.

The negotiation of the toll for the Tournon-Tain suspension bridge is the subject of difficult negotiations between the Seguins and the governmental administration.

It takes into account the estimated price of the bridge (190,000 francs), an exceptionally low price compared to masonry bridges, and the traffic previously recorded by the ferry that it replaced.

The latter’s toll was ultimately more or less renewed for the benefit of the Seguins, which proved to be most beneficial for them.

Indeed, the Tournon-Tain structure is immediately overwhelmed by considerable traffic.

The Seguin brothers, who had anticipated the technical commercial success of the bridge, finally decided to do without the anticipated shareholders, the bourgeois of the two towns, and to assume the construction risk alone.

It was a complete success and Marc Seguin saw it, a few years later, for his family as “the beginning of our fortune”.

Authorization for the Tournon-Tain bridge was obtained at the end of 1823.

The bridge was to be built at the ‘contractors’ own risk’, in only 18 months, which was extremely rapid given the technical means of the time.

The work begins in the spring, and they experienced the hazards of a very new construction site as well as those of a river with violent and devastating floods.

The high waters of November 1824 stopped the construction site for many weeks and, ultimately, destroyed a large part of the pile works where the pouring of hydraulic concrete had begun.

They had to start again!

The Seguin brothers courageously resumed work on December 15.

A certain number of documents have been preserved in the company’s archives, giving an idea of the work carried out and the conditions of such a site.

Invention of the thin iron wire cable

Among the innovative practices of the Tournon-Tain bridge, that of fine iron wire cables attracts particular attention.

Seguin also widely highlights it as the key to the success of the suspension bridge in his book Des ponts en fil de fer (Wire Suspension Bridges).

This is one of the bases of the project, because the French civil engineer understood the weaknesses of English forged chains as well as their great difficulty of manufacturing in a country like France in the 1820s.

Using iron wire from Franche-Comté, of which this is one of the specialties, he assembles them into bundles of numerous parallel wires with a section of 3 mm. It thus reduces the risk of breakage and benefits from their better resistance compared to forged bars.

He presented this discovery of resistance of materials to the Academy of Sciences in September 1823.

This scientific success led to the acceptance of the proposal by the ‘Ponts et Chaussées’ (Bridges and Road administration), until then opposed to the suspension wire cable which they judged to be too uncertain and never used before by the English.

The parapet’s rigidity structure

If the idea of the fine wire for the suspension cables appeared at the origins of the project, other innovations were gradually dictated by the reality of the test footbridges on the Cance in Annonay, then on the Galaure in Saint-Vallier: the suspension bridge oscillates as its users pass by!

A particularly difficult problem to control and understand physically (the mechanical resonance of elastic structures).

With the help of his collaborators, notably the master carpenter Barjot, he gradually imagined an apron with a rigid structure; and this is a field where the Ardèche engineer is once again doing pioneering work on an international scale.

This structure is remarkable.  It is the first large suspension bridge built in continental Europe,

following initial tests carried out in the United States and Great Britain.  It brings a major innovation, by replacing the forged chains traditionally used for British bridges with thin stell wire cables.

The Tournon-Tain suspension bridge brings back the possibility of crossing a river like the Rhône, with its strong currents and flash floods, with a permanent structure.

It is a light structure, quick to build, relatively inexpensive and requiring only a central pile and superstructures to support the suspensions.

In addition to the cable, it provides a set of innovative solutions that make it possible. The success of the new bridge is immediate, and its replication in the Rhône valley is rapid, with around ten new structures of this type in the following five years, between Lyon and the Mediterranean, then throughout France, Switzerland and Europe. In the United States as well.

The original historic bridge opened in 1825 between Tournon and Tain and had to be demolished in 1849 due to higher clearance required for the passage of the new steamboats. It was then replaced by a bridge of the same type, wider, which was built about a hundred meters downstream, by the same Marc Seguin and following the same technological principles. This is the current footbridge on which you are standing.

The foundations of the 1825 bridge were reused to establish a small raised footbridge which was long confused with the original bridge and which was definitively demolished in 1967.

Visual rendering of the 1825 Historical Bridge created by Archéovision and MCC-Heritage

The foundation of the piers of a bridge in the Rhône was a particularly difficult challenge due to the currents and rapidly variable water levels, even in summer.

The choice of the suspension bridge reduced the construction to a single central pier, which also limited the disruption to navigation.

One of Seguin’s advantages in his business is the presence, near the site, of lime from Monsieur de La Farge (today the Lafarge group), in Le Teil (Ardèche), which has the very rare property of being hydraulic, that is to say allowing concretes that set and harden under water.

This use was actually known for a long time in the Rhône valley, as a regional know-how. Seguin then uses this property on a large scale, pouring concrete masses between submerged formworks.

They form the “sole” of the foundations and they are surrounded by large blocks of rock to limit the scouring effects of the current.

The reinforced concrete.

In the construction of his first Rhône bridge, Seguin faced considerable and often new, challenges.

With his collaborators, he was on the lookout for any innovative idea that could strengthen the quality of his work.

To ensure the stability of the three gantries supporting the cables, which he feared would crack under the repeated tension of the cables, he included large vertical iron rods within the concrete of the « straight legs », which he wedged at their ends by sealed stones.

These metal bars can be stressed in tension while the concrete resists through its compressive qualities. It is “reinforced concrete”, almost 25 years before the first patent was filed on this material !

But this is a “manufacturing secret” that only the site archives reveal, and not the printed texts of the time.