Pont Saint-Martin

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Coordinates: 45 ° 35 ′ 58 ″  N , 7 ° 48 ′ 0 ″  E

Pont Saint-Martin
Pont Saint-Martin
Pont Saint-Martin
Convicted Connection Po Valley - Gaul
Crossing of Lys
place Pont-Saint-Martin ( Italy )
construction Segment arch bridge with vaulted vaults
width 5.8 m
Number of openings 1
Clear width 36.65 m or 31.4 m
Arch thickness (vertex) 1.03 m
Arrow ratio 3.3 to 1
Arch slenderness 34 to 1
construction time between 27 BC BC and AD 14
location
Pont Saint-Martin (Aosta Valley)
Pont Saint-Martin

The Pont Saint-Martin ( Walser German : Martinstäg ) is a Roman segment arch bridge in the village of the same name Pont-Saint-Martin in the Aosta Valley in Italy . With a span of approx. 36 m (according to other information 31.40 m) and a vault thickness of only around one meter, the single arch construction is one of the largest and most daring bridges of antiquity . The Pont Saint-Martin has served traffic for more than two thousand years.

Traffic situation and dating

The Pont Saint-Martin is located in the municipality of the same name at the entrance of the Aosta Valley, where it crosses the Lys mountain stream just before it flows into the Dora Baltea river . The bridge was part of a transalpine Roman road through the Aosta Valley, which led over the Great and Small St. Bernhard to Gaul and was built in the 2nd and 1st centuries BC. In the course of the Roman expansion over the Alps was gradually expanded. The construction of the bridge that stands today is likely to have taken place in the time of Emperor Augustus , who after taking the city of Aosta in 25 BC. And its re-establishment as a Roman colony Augusta Praetoria had the local road system completely renewed. The foundation of hewn stone blocks, which clearly stands out from the quarry stone cladding above, has given rise to the assumption that a previous building with a similarly large span dates back to 141 or 120 BC. B.C. when the first military roads were built in the valley, but because of the not yet fully developed concrete technology, it did not last long.

construction

Underside of the arch vault

In terms of construction , the Pont Saint-Martin stands out from the typical Roman bridge with a number of special features, in particular its unusually large span and the extremely thin arched arch, which also has a circular segment shape.

The clear width of the bridge is approx. 36.65 m (or 31.4 m), making the structure one of the largest Roman bridges still standing. The width is 5.80 m, with the parapet on both sides narrowing the driveway to 4.60 m. The height from the transom points to the road surface is 12 m and up to the upper end of the parapet 13.60 m.

The Pont Saint-Martin is one of the few flat arch bridges of antiquity. The center of the arch is 5.80 m below the fighter points, which means that the barrel vault describes a section of a circle of 144 degrees. With a ratio of clear span to elevation of approx. 3.3 to 1, the bridge differs quite clearly from the typical Roman semicircular arch bridge, in which only two meters in length were gained by one meter in height. The flatter arched profile resulted in material savings in the vertical, but also made stronger abutments on the embankment necessary in order to be able to absorb the higher lateral pressure. The neighborhood to the Pont de Pierre in Aosta, which is on the same stretch of road and was also built under Augustus, could indicate a local concentration of segmental arch technology.

The special character of the Pont Saint-Martin can also be recognized by its 71 supporting wedge stones, which are only about 1.03 m thick. According to Colin O'Connor, the ratio of arch thickness to clear span is the most important parameter when building stone arch bridges. Roman builders usually took a more conservative approach, avoiding arch strengths less than 1/20 of the span for larger bridges. This value drops to a bold 1/34 at the Pont Saint-Martin, which was unsurpassed among the more than forty Roman bridges examined by O'Connor.

Other preserved Roman bridges in the Aosta Valley are the Pont de Pierre and the Pont d'Aël .

Individual evidence

  1. ↑ a b c O'Connor (1993), p. 171.
  2. ↑ G. Frunzio et al. (2001), p. 592.
  3. ↑ a b c d e f g h i j k O'Connor (1993), p. 89f.
  4. ↑ a b c O'Connor (1993), p. 169 (Fig. 140)
  5. ↑ a b O'Connor (1993), p. 167.
  6. ^ O'Connor (1993), p. 170.
  7. ^ O'Connor (1993), pp. 170f.

literature

See also

Web links

Commons : Pont-Saint-Martin (bridge)  - Collection of images, videos and audio files