Pergamon Bridge
Coordinates: 39 ° 7 ′ 18 ″ N , 27 ° 10 ′ 58 ″ E
| Pergamon Bridge | ||
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| use | Substructure for the forecourt of the Red Hall | |
| Crossing of | Selinus ( Bergama Çayı ) | |
| place | Pergamon ( Turkey ) | |
| construction | Arch bridge with vaulted vaults | |
| width | 183-196 m | |
| Number of openings | 2 | |
| Clear width | 9 m | |
| Arrow height | 4.5 m | |
| Clear height | 7.5 m | |
| construction time | Hadrian's time (AD 117-138) | |
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The Pergamon Bridge is a Roman river construction in the ancient city of Pergamon (today: Bergama ) in Turkey . The double tube under the forecourt of the Red Hall is by far the largest river overburden in antiquity with a length of 183 or 196 m.
Classification as a river development
The Pergamon Bridge , which is entirely above ground, is often misleadingly referred to as a tunnel in specialist literature because of its unusual width . Although it has hydraulic and hydrological properties comparable to those of a tunnel , completely different construction techniques were used in its construction, since, given its position above ground, neither determining the direction of advance nor the risk of water ingress or slab collapses played a role. According to Klaus Grewe , it therefore makes more sense to speak of a river superstructure, the construction of which corresponds to that of a particularly wide bridge, in which the weight of the barrel vault is absorbed by the abutments and the wall between the two tubes performs the static function of a central pillar .
In terms of urban planning, such substructures are particularly useful when in the middle of the city - in the best location, so to speak - a large open space is to be gained for public or other buildings. This was also the case in Pergamon, where at the time of Hadrian (r. 117-138 AD) a considerable part of the city river Selinus (today: Bergama Çayı ) was bridged to make room for the forecourt of the Temple of the Egyptian Deities (also known as Serapis Temple or Red Hall ) (another example in Asia Minor is the Nysa Bridge ).
construction
The river superstructure of Pergamon consists of a straight double tube with two parallel barrel vaults, between which a continuous partition runs. The difference in length between the western (183 m) and eastern tube (196 m) results from the fact that the tunnel openings - which are at the same height on the mountain side - end offset 13 m on the valley side. As a result of a later built-in threshold of 2 m height, the west tunnel is now partially silted up. The dimensions of the two semicircular arches are practically identical: the span is 9 m each, the stitch height from the fighter point to the top of the arch is 4.5 m and the clear height is 7.5 m. The vaults made of unworked stones in a solid mortar bond lie on both sides on a substructure made of stone blocks.
Above and below the river superstructure, two well-preserved ancient bridges cross the Selinus, the Tabak Köprüsü and the Üç Kemer Köprüsü (“three-arch bridge”).
Flow capacity
The limit capacity of the river overburden during flooding was the subject of hydraulic and hydrological studies. With a gradient of 0.6%, a maximum flow capacity of 360 m³ / s per tunnel tube was determined before the Selinus accumulates, puts the structure under internal pressure and causes damage. If this value is based on the fact that the Selinus is 13.4 km long, has an average gradient of 2.2% and a catchment area of 101 km², the following average return intervals result, depending on the method :
- 250 years (Günerman method)
- 550 years (DSI method)
- 1,100 years (Mockus method)
- 8,500 years (Snyder method)
According to this, statistically every 700 years - the value that Grewe describes as the " arithmetic mean " - a flood would be expected that would exceed the capacity of the Pergamon Bridge.
Individual evidence
- ^ Grewe, Klaus et al. (1994), pp. 350,352
- ↑ a b All information: Grewe, Klaus et al. (1994), pp. 348f.
- ↑ All information: Grewe, Klaus et al. (1994), p. 350
- ^ Grewe, Klaus et al. (1994), p. 349
- ↑ All information: Grewe, Klaus et al. (1994), pp. 351f.
literature
- Klaus Grewe, Ünal Özis and others: The ancient river structures of Pergamon and Nysa (Turkey). In: Ancient World . Vol. 25, No. 4, 1994, pp. 348-352.
- Ünal Özis et al .: Flood Flows and Capacities of the Historical Pergamon and Nysa Tunnels in Anatolia. In: International Association for Hydraulic Research (IAHR), 18th Congress Proceedings. Vol. 6, Cagliari 1979, ZDB -ID 998222-x , pp. 696-698.
- Ünal Özis: Ancient Water Works in Anatolia. In: Water Resources Development. Vol. 3/1, 1987, ZDB -ID 1251957-1 , pp. 55-62.
