Puente de Alconétar
Coordinates: 39 ° 45 ′ 14 " N , 6 ° 26 ′ 14" W.
| Puente de Alconétar | ||
|---|---|---|
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| Crossing of | Tagus | |
| place | Garrovillas de Alconétar , Province of Cáceres , Extremadura ( Spain ) | |
| construction | Segment arch bridge with vaulted vaults | |
| overall length | 290 m (including bridge ramp) | |
| width | 6.55-6.80 m | |
| Number of openings | Approx. 18 (with flood outlets) | |
| Clear width | 7.20-15 m | |
| Pillar strength | Approx. 4.4 m | |
| Arch thickness (vertex) | 1.20 m (2nd flood passage) | |
| Arrow ratio | 4-5: 1 | |
| Flow profile | 73% | |
| Arch slenderness | 6: 1 (2nd flood passage) | |
| height | Min. 12.50 m | |
| construction time | Probably between 98 and 138 AD | |
| Status | ruin | |
| location | ||
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All values are based on measurements before relocation and are necessarily fragmentary due to the state of destruction. The remains of the bridge were moved to a new location 6 km upstream in 1970. |
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The Puente de Alconétar ( Spanish for "Bridge of Alconétar"), also known as Puente de Mantible , was a Roman segment arch bridge in the province of Cáceres in the Spanish region of Extremadura . The ancient building with its flat arches ( arrow ratio of 4–5: 1) is one of the earliest examples of this type of bridge. Due to its design, it is believed that the bridge was built in the early 2nd century AD under the emperors Trajan or Hadrian , possibly under the guidance of Apollodor of Damascus , the most famous master builder of his time.
The almost 300 m long Alconétar Bridge carried the Via de la Plata , the most important north-south connection in western Hispania , over the Tagus , the longest river on the Iberian Peninsula . It remained in operation until the Reconquista , and numerous recent attempts at reconstruction by Spanish engineers failed. The remains of the bridge, which essentially stood on the right bank of the river, were brought to safety in 1970 before the Alcántara reservoir was flooded .
Location and road connections
The historic Puente de Alconétar, which should not be confused with the monumental bridge of Alcántara further downstream, spanned the Tagus not far from the mouth of the Almonte in the heart of the Spanish province of Cáceres in the Extremadura region. The convenient location of the Roman Bridge between northern and southern Spain is underlined by a modern expressway and a railway line that cross the Tagus in the immediate vicinity. The now visible bridge ruin was moved in 1970 when the Alcántara dam was built from its original location to a meadow 6 km to the north near the municipality of Garrovillas de Alconétar . On the other hand, no significant remains of the neighboring ancient bridge over the Almonte have survived.
In ancient times , the Alconétar Bridge belonged to the Roman road Iter from Emerita Caesaraugustam , later also called Via de la Plata . This important inner-Iberian connection led in a south-north direction from the provincial capital Mérida through the river valleys of the Alagón , Tiétar and Tajo down to the western Meseta with its capitals Salamanca and Zamora . Their end point was in Astorga in the northwest. The Via de la Plata was one of the four main routes built by Augustus (30 BC – 14 AD) and his successors for the military control of the peninsula and for the exploitation of the rich Spanish gold and silver deposits.
In addition to the transition over the Tagus, the remains of four other ancient bridges can be identified along the road, namely over the Albarregas, the Aljucén, near Cáparra and over the Tormes . On the heights above the Alconétar bridge, a Roman mansio with the name Turmulus (Spanish Ad Túrmulos ) was set up , as it corresponded to the distance intervals at that time, the fourth of a total of sixteen in the section between Mérida and Astorga .
history
The exact construction date of the Puente de Alconétar is unknown due to the lack of literary or epigraphic information. Their segmental arches suggest, however, a dating to the early 2nd century AD, namely the era of Emperor Trajan (98–117 AD), who himself came from the Spanish province of Baetica and when he came to power the Iter from Emerita Caesaraugustam had it repaired. Segmental arches were often used by Trajan's court architect Apollodor von Damascus, for example in the Trajan's Forum and above all in the largest civil engineering structure of the time, the wooden Trajan's Bridge , which spanned the over 1000 m wide Danube on 20 huge concrete pillars and was used for the march in the Dacer Wars .
Even Arab geographers silent about the ancient bridge, although they also leading over the Tagus Roman Bridge of Alcántara praise to the skies. After all, the existence of a town called Alconétar, Alconétara or Alcontra ( Arabic: small bridge ) can be temporarily proven for the 13th century - possibly an indirect reference to the towering Alcántara Bridge. It also remains unclear why the Alconétar Bridge is known locally as the Puente de Mantible , an allusion to the legend of Charlemagne and his Twelve Paladins .
The bridge probably remained in use until the Reconquista, when the Tagus River formed the border between Christian and Arab domains from the 11th to the 13th centuries , and the frequent fighting could easily have rendered the ancient structure unusable. According to another theory, the slow erosion of the ancient foundations could have had a negative impact at that time.
The Puente de Alconétar was first mentioned in a document in 1231 and - now expressly under traffic - in 1257. It was probably repaired by the Knights Templar who had taken the bridge and the village of Alconétar under their care in the meantime; Repair sheets 1 and 3, which are still visible today, are said to date from this time. As early as 1340, however, the river crossing seems to have been unusable again, so that boats were used to cross over, the use of which is documented for later times. At the site of the ancient resting place, a fortress was built in the Middle Ages , the tower of which is made of Roman Spolia and now protrudes from the reservoir when the water is low.
Numerous attempts in modern times to put the bridge back into operation were unsuccessful: in 1553 the architect Rodrigo Gil de Hontañón estimated 80,000 ducats for the repair without his plans being implemented. Even the building project by Alonso de Covarrubias and Hernán Ruiz in 1560 did not get beyond the planning stage, nor did another project between 1569 and 1580.
In the 18th century, two further attempts at repair failed in 1730 and 1760–70; in the latter, the plans of the military engineer José García Galiano envisaged a completely new building with three wide-span flat arches. The plan drawing shows that the bridge arches that have been preserved were already limited to the right bank at that time, as confirmed by the elevation by Fernando Rodríguez from 1797 and the excellent engravings in Alexandre de Labordes Voyage pittoresque de l'Espagne a few years later. Rodríguez's attempt at reconstruction by drawing (see graphic below) shows an evenly rising bridge profile, which is defined in the middle of the river by three central round arches, which are flanked on both sides by nine further segmental arches. The symmetrical character of the arches indicates that in ancient times there could have been another segmental arch instead of the bank reinforcement seen upstream on the right.
The basis of the modern scientific examination of the Puente de Alconétar is the study by the road construction engineer Antonio Prieto (1925), which shows the state of the bridge before it was laid. Although efforts were made to rebuild the building true to the original, according to Durán, minor changes to the structure cannot be ruled out in principle.
The Puente de Alconétar has been listed as "historical heritage" by the Spanish authorities since 1931 (as of 2010).
construction
The main characteristic of the Puente de Alconétar was its flat segmental arches, which were rarely used in ancient bridge construction. According to Prieto, the bridge had sixteen arches with the following spans (estimates in brackets, all in meters) without the two high water culverts on the right driveway :
- 7.30 - 8.20 - 9 - 10.15 - (11 - 12 - 13 - 14 - 15 - 14) - 13 - 12 - 11 - (10) - 9.30 - 9.10.
Other specifications, however, range from eleven to fifteen sheets. The total length of the straight structure was 290 m, 190 m of which was used to bridge the river bed at low tide. Adding the clear arch widths and assuming an average pier thickness of 4.4 m on the basis of the pillars obtained , the distance between the two bridge ramps was 244 m (= 178 + 15 × 4.4), which corresponds to a river cross-section of 73%. For comparison: the corresponding values for the Roman bridges to Córdoba , Mérida and Salamanca are 62%, 64% and 80%.
Before the relocation, the structure that had been preserved was concentrated on the right bank of the Tagus, where the current was less strong; a number of pier stumps protruded from the middle of the river just above the surface of the water, while on the left bank two piers still stood upright, to which the left abutment was attached. The bridge parts moved in 1970 were essentially (see photos): the right bridge ramp with its two arched flood openings, the pillars 1, 2, 3 with the remains of 4 and 6 and the arches 1 and 3. The few other remains sank into the 1970s Floods of the Alcántara reservoir.
The ramp has a length of 42 m and a width of 6.55–6.80 m. The clear widths of the two segment arches in the abutment are 6.95 m and 7.40 m, which corresponds to an elevation of 4.0 and 3.3 to 1, respectively. The precisely fitting inclined support surface for the fighting stones clearly demonstrates the Roman origin of these arches. The 1.20 m thick wedge stones appear heavily oversized in relation to the span (ratio of 1 to 5.8 or 6.2). The two surviving bridge arches No. 1 and 3, on the other hand, are substitute arches with poor load-bearing capacity made of uncleanly walled rubble stones; their age, like all repair work, is unknown; they may date from the time of the Knights Templar.
The masonry of the first two bridge piers above the lower cornice , which protrudes at the same height on all pillars, is also recognizable after the antique period . The superstructure of the pillars could have been reconstructed for a drawbridge or a tower, which, according to a picture in the picturesque Voyage, sat on pillar 2. In contrast, the Roman structure of the third pillar has been preserved up to the top of 12.50 m; the carefully worked ashlar masonry and the second cornice, which ran through all the ancient pillars, give the clearest impression of the original form of the Roman bridge.
In particular, the arrow height of the original segmental arches can be reconstructed very precisely on the basis of the angle of the inclined support surface for the arch attachment . Accordingly, the third arc originally described a section of a circle of 95 °, which suggests an arrow ratio in the range of 4-5 to 1 for the remaining segment arcs. This value is supported by the engravings de Labordes, according to which an intact Roman segmental arch spanned the neighboring fourth yoke at the beginning of the 19th century. This makes the Alconétar Bridge - along with other early examples such as the Limyra Bridge or the Ponte San Lorenzo - one of the oldest segment arch bridges in the world and bears witness to the fact that Roman bridge builders, contrary to previous doctrines, were familiar with the flat arch.
The pillar strengths increase slightly to 4.25 m, 4.45 m, 4.55 m and 4.80 m towards the middle of the river, while the intervals between the piers increase from 7.30 m to 10.20 m. The fifth and last surviving river pillar has by far the largest cross-section (8.10 m) under the significant name of the 'table of the bishop' and stands as a solitaire far forward in the river bed. It may be a medieval pillar that could have been erected instead of two ancient arches as the foundation for a defense tower. All five pillars are reinforced on the upstream side with pointed breakwaters.
The shell wall of the bridge piers consists of locally cut granite blocks , which were built up without mortar or anchor connections using the opus-quadratum method; As with many Roman bridges, the interior of the pillars and ramps was filled with Roman concrete . Externally, the arches, which were exceptionally flat for ancient times and later times, should have given the structure a rather squat profile, so that the roadway ran either horizontally or slightly rising on both sides.
Reconstruction and dimensions
| Bridge part | Galiano (ca.1770) |
Rodríguez (1797) |
Prieto (1925) |
Durán (2004) |
|---|---|---|---|---|
| Span of 1st flood passage | 6.86 | 7.04 | 7.00 | 6.95 |
| Ramp strength | 10.60 | 11.63 | 12.00 | 14.00 |
| Span of 2nd flood passage | 7.40 | 7.10 | 7.50 | 7.40 |
| Ramp strength | 12.90 | 11.65 | 13.00 | 13.50 |
| Span of 1st arch | 7.50 | 7.62 | 7.30 | 7.30 |
| Strength 1st pillar | 5.60 | 4.17 | 4.25 | 4.25 |
| Span of 2nd arch | 9.00 | 8.44 | 8.20 | 8.10 |
| Strength 2nd pillar | 5.60 | 4.19 | 4.25 | 4.45 |
| Span of 3rd arch | 9.86 | 8.92 | 8.95 | 8.50 |
| Thickness 3rd pillar | 5.50 | 4.21 | 4.25 | 4.55 |
| Span of 4th arch | 10.10 | 10.32 | 10.15 | 10.20 |
| 4th pillar thickness | 4.81 | 4.80 | ||
| Span 5th arch | 12.03 | (11.00) | ||
| Thickness 5th pillar | 6.21 | |||
| Span 6th arch | 16.72 | (12.00) | ||
| Thickness 6th pillar | 6.21 | |||
| Span 7th arch | 8.92 | (13.00) | ||
| Thickness 7th pillar | 6.21 | |||
| Span 8th arch | 16.74 | (14.00) | ||
| Thickness 8th pillar | 6.21 | |||
| Span 9th arch | 11.93 | (15.00) | ||
| Thickness 9th pillar | 4.79 | |||
| Span 10th arch | 10.22 | (14.00) | ||
| Thickness 10th pillar | 4.19 | |||
| Span 11th arch | 8.82 | 13.00 | ||
| Strength 11th pillar | 4.19 | |||
| Span 12th arch | 8.38 | 12.00 | ||
| Thickness 12th pillar | 4.19 | |||
| Span 13th arch | 11.00 | |||
| Thickness 13th pillar | ||||
| Span 14th arch | (10.00) | |||
| Thickness 14th pillar | ||||
| Span 15th arch | 9.30 | |||
| Strength 15th pillar | ||||
| Span 16th arch | 9.10 |
See also
literature
- Antonio Prieto Vives: El Puente Romano de Alconétar . In: Archivo Español de Arte y Arqueología , Vol. 2 (May / Aug. 1925), pp. 147–158.
- Carlos Fernández Casado : Historia del Puente en España. Puentes Romanos: Puente de Alconétar . Instituto Eduardo Torroja de la Construcción y del Cemento, Madrid 1970 without page numbering .
- Colin O'Connor: Roman Bridges . Cambridge University Press 1993, ISBN 0-521-39326-4 , pp. 108f., 171.
- Luis García Iglesias: Alconétar, Cáceres, Spain . In: Richard Stillwell et al. a. (Ed.): The Princeton Encyclopedia of Classical Sites. Princeton University Press, Princeton NJ 1976, ISBN 0-691-03542-3 .
- Juan Gil Montes: Via Delapidata . In: Elementos de la Ingeniería Romana , Congreso Europeo: Las Obras Públicas Romanas, Tarragona 2004.
- Manuel Durán Fuentes: La Construcción de Puentes Romanos en Hispania . Xunta de Galicia, Santiago de Compostela 2004, ISBN 978-84-453-3937-4 , pp. 181-87.
- Teresa González Limón et al .: A Brief Analysis of the Roman Bridges of the Way "La via de la Plata" (PDF; 386 kB). In: PB Lourenço, P. Roca (Ed.): Historical Constructions . Guimarães 2001, pp. 247-256.
- Vittorio Galliazzo: I ponti romani. Catalogo generale , Vol. 2, Edizioni Canova, Treviso 1994, ISBN 88-85066-66-6 , pp. 358-361 (No. 755).
Web links
Remarks
Individual evidence
- ↑ Durán 184; Fernández: Puente de Alconétar; Prieto 150
- ↑ Prieto 155; O'Connor 108f .; Galliazzo 359
- ↑ a b c O'Connor 20
- ↑ a b Prieto 147
- ↑ a b c O'Connor 108f.
- ↑ a b c d Prieto 149
- ↑ a b c Durán 182
- ↑ Durán 91f.
- ↑ Gil 9f.
- ↑ a b Prieto 155
- ↑ Prieto 155; O'Connor 108f.
- ^ O'Connor 142f.
- ↑ Prieto 10f.
- ^ Prieto 158
- ↑ a b Prieto 155f .; Duran 182
- ↑ a b c d e Prieto 157f.
- ↑ a b c d Fernández: Puente de Alconétar
- ↑ a b Durán 183
- ↑ Durán 181, 184
- ↑ Patrimonio histórico: Bienes culturales protegidos. Consulta de bienes inmuebles. Bien: "Puente de Alconétar"
- ↑ Prieto 149f .; Fernández: Puente de Alconétar; O'Connor 108f.
- ↑ a b c d e Durán 184
- ^ O'Connor 165
- ↑ Prieto 150f.
- ^ Galliazzo 358
- ↑ González 250, Tab. 2
- ↑ Prieto 149f .; Fernández: Puente de Alconétar; O'Connor 108f .; Duran 184
- ↑ Prieto 150; Durán 183
- ↑ a b c Prieto 150
- ↑ Prieto 152; Durán 185f.
- ^ O'Connor 171
- ^ Prieto 151
- ↑ Prieto 150, Fig. 3
- ↑ Prieto 152; Fernández: Puente de Alconétar; Galliazzo 359
- ↑ Durán 186f.
