Pontoon bridge

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Pedestrian pontoon bridge over Lake Okutama , Japan

A pontoon bridge (also ship bridge or floating bridge ) consists of a series of pontoons , ships, boats or other floating bodies floating on a body of water , on which a pier, a bridge deck or, in rare cases, a track is mounted.

Description of the pontoon bridge

Types of use

Since a pontoon bridge does not require any foundations, bridge piers or abutments, it can usually be erected faster and cheaper than a permanent bridge . It can also be built where a great depth of water or the low load-bearing capacity of the subsoil would not allow a fixed bridge or would only allow a disproportionately large effort.

There are therefore typically three types of use of pontoon bridges:

  • for a short term purpose, typically as part of a military movement of forces;
  • permanently, for structural reasons, for cost reasons or to be able to move away from the bridge (e.g. Queen Emma Bridge );
  • as a makeshift replacement of a destroyed fixed bridge, typically as a result of war.

Pontoon bridges can be designed as pedestrian, single or multi-lane road bridges and also as railway bridges.

Types, orders of magnitude, materials

Simple pontoon bridges

In the simplest case, pontoon bridges can consist of a series of connected floating plastic elements that form a bathing jetty or the jetty around an open swimming pool by the sea.

Pontoon bridges often consist of a series of locked metal barrels or boxes on which a handrailless footbridge is mounted, which, for example, allows access to the boats in a marina and rises and falls with them according to the water level. In the case of small pedestrian bridges, a railing consisting of a rope or thin metal rods is mounted on the footbridge.

Bradley armored personnel carrier leaves pontoon bridge in Iraq

Military pontoon bridges for troop movement in wars

For use in the military , especially for crossing rivers and canals, there are standardized transportable pontoons that have a roadway made of metal planks or wooden planks . The pontoons can be closed metal bodies or flat, stackable hulls or even durable inflatable boats. The individual elements are designed and coordinated in such a way that they can be assembled and dismantled easily and quickly, but still have the required load-bearing capacity, e.g. B. for tanks. For reasons of weight, military pontoon bridges have only a low height above the water surface and short distances between the pontoons.

In the disaster relief -like bridges are used.

Permanent pontoon bridges

Earlier, permanent bridges over larger rivers typically consisted of wooden ships or boats connected with wooden planks. A deck made of boards and a wooden railing on both sides were attached to it.

Today's civil pontoon bridges often consist of steel pontoons and deck girders, are usually higher than military bridges in order to be protected from waves and spray, and have railings, guardrails and similar devices known from fixed bridges.

The modern two-lane Nordhordlandsbrua in Norway has ten pontoons at intervals of 113.25 m each, on which a 5.5 m high steel box girder bridge lies, which in turn is located 5.50 m above the water level. A ramp is mounted on one end of this bridge section, which leads up the roadways to the adjacent cable-stayed bridge at a height of more than 30 m.

While short pontoon bridges are only a few meters long, the Governor Albert D. Rosellini Bridge is 2310 m long, making it the longest existing pontoon bridge.

Large, floating road bridges with several lanes lie on hollow bodies made of reinforced concrete , which are the size of a building and can weigh 11,000 tons. The lanes including railings, guard rails and light masts do not differ in any way from the lanes of solid bridges.

anchoring

Typically, each pontoon is secured in position with anchors at both ends . This means that a largely straight bridge is possible. However, if the water is so deep that anchoring is no longer sensible, only the outer pontoons are attached to the respective bank. The middle pontoons are simply connected to each other and float freely in the water. In this case, the pontoons form a long, arched line between the banks due to the current or wind.

Changing altitude

The floating bridge naturally rises and falls as the water level changes. A rising water level results in an increase in the distance between the banks on sloping bank slopes. On the other hand, the difference in height between the road on the bank and the bridge changes. Therefore, special precautions must be taken to adjust the length of the bridge and to compensate for the changed height difference with ramps or the like. Occasionally, bridge segments are held that are swum in when the river rises to lengthen the bridge.

Since railways can only negotiate small gradients, pontoon bridges over bodies of water with strongly fluctuating water levels are usually out of the question for them.

Closure of the water

Ship bridge with bascule bridge in Deventer , Netherlands, ca.1910

Pontoon bridges without special precautions block the water not only to shipping traffic, but also to trees, bushes and rubbish washed up by rivers. In the case of military bridges that are only used for a short period of time, this often does not have to be taken into account, but it does need to be taken into account for long-term bridges on navigable waters.

In these, therefore, raised sections are often installed as passages. In the Netherlands, a (floating) bascule bridge is often installed in the course of the pontoon bridge to allow shipping traffic to pass . In other cases, a part of the bridge is cut off and floated out so that it can be reinstalled after the ships have passed. Sometimes the bridge as a whole or a large part is swiveled towards the bank and pulled back to its original position after the ships have passed. To avoid these cumbersome procedures, the pontoon bridge is occasionally combined with a conventional bridge with a greater clearance.

Special properties of pontoon bridges

Various peculiarities occur with pontoon bridges. When stepping on a small pontoon jetty in a marina or driving a temporary bridge with a heavy vehicle, it is clearly noticeable: The pontoon bridge sinks more locally depending on the load (and the impact) and thus generates the necessary additional buoyancy. A bridge intended for vehicles must therefore be made sufficiently rigid in the longitudinal direction or provided with pontoons that are sufficiently close to one another to prevent individual loads from sinking in too much. Pontoon bridges are seldom suitable for railroads because the sinking locomotive has to constantly drive uphill and quickly reaches the limits of its climbing ability, even if there are no special gradients on the bank. The sinking of the pontoons driven over also creates a wave in the water, which lifts the following pontoons and, from a certain speed, the bridge elements in front of the heavy vehicles can rise to a kind of hump, which can lead to vibrations and overstressing of the bridge.

On narrow makeshift bridges, two-lane vehicles are often guided through recessed lanes in the middle of the roadway, as off-center loads cause pontoon bridges to tip over to the side. When overloaded, a pontoon is temporarily submerged. Tires and other cavities in a vehicle then also create lift. Correspondingly, the grip of the tires on the road surface is reduced and flow forces can shift the vehicle sideways. Waves with a sufficiently long wave length raise and lower smaller pontoons.

When planning a pontoon bridge, therefore, not only the dead weight of the bridge and the weight of the users must be taken into account, but also various dynamic factors such as the speed and distance of the vehicles as well as loads from currents, wind and waves.

Damage can be caused by unforeseen floods, raging currents, storms, strong waves, ice drifts, floating debris and collisions with ships.

history

Larger rivers that could not be crossed on a ford were already crossed with pontoon bridges when the construction of such large solid bridges was not yet possible. Pontoon bridges can be found in Assyria and Babylonia up to the 9th century BC. Trace back to BC. In China, too, the first pontoon bridges were probably made in the 9th or 8th century BC. Built.

The ship bridge over the Bosporus , built by the Persian great king Dareios I in 513 BC. BC on the occasion of his campaign against the Scythians is the first that Herodotus reports. From Herodotus' simple mention that Dareios ordered not only the delegation of soldiers and warships but also the bridging of the Bosporus in preparation for his campaign , it can be seen that the construction of pontoon bridges was already a matter of routine at this time, even if a bridge was over the at least 700 m wide Bosporus with its strong current was an outstanding achievement.

Herodotus also describes that Darius I also crossed the Danube on a pontoon bridge during this campaign , probably near Isaccea .

The ship bridges over the Hellespont , today's Dardanelles , over the Xerxes I. 480 BC. BC moved to Greece in the 2nd Persian War , are described in detail by Herodotus, although certain details seem unbelievable. Here, too, the orders for the provision of ships for the bridges and for the manufacture of ropes are only mentioned under the other measures to prepare for the campaign.

Roman ship bridge

Alexander the Great crossed the Hellespont in May 334 with an army of around 35,000 Macedonians and Greeks with the help of ships, but in the course of his campaigns he built ship bridges over some rivers. Hannibal had a floating bridge built over the Ticino during the Second Punic War . Caesar had floats woven from willow branches and covered with animal skins, which were easy to transport and quick to use. In Arelate , today's Arles , the Romans built a 280 m long bridge over the Rhone , the middle part of which was a pontoon bridge. Also in the 11 BC Founded Mogontiacum ( Mainz ) in the 4th century BC, there was initially a pontoon bridge over the Rhine until it was replaced shortly afterwards by a wooden bridge to Mainz-Kastell and in AD 71 by a stone pillar bridge with a wooden superstructure. No traces have been found of the bridge over the Euphrates in Zeugma , the Hellenistic-Roman city in today's Turkey, but it is assumed that it was a stone arch bridge with a section as a pontoon bridge.

According to Suetonius , the Roman emperor Caligula is said to have built a ship bridge over the Gulf of Pozzuoli between Puteoli, today's Pozzuoli and the opposite Baiae , today Baia , near Naples , probably to deny the prophecy of the astrologer Thrasyllos that Caligula could rather cross ride the Bay of Baiae as an emperor. The bridge consisted of numerous merchant ships that were anchored in a double row and covered with a layer of earth, so that a road similar to the Via Appia was created. Caligula rode back and forth on the bridge or drove in a car for two days.

In the centuries that followed, it became customary to carry swimming bridge equipment on campaigns. Ammianus Marcellinus reports that on his Persia campaign , Emperor Julian crossed several rivers with floats made of wickerwork and animal skins and that his opponent, the Sassanid king Shapur II, also built a bridge over the Tigris . The Eastern Roman Emperor Justinian (527-565) had the Sangarius Bridge built over the Sangarius River (modern: Sakarya ) in what is now Turkey , after the pontoon bridge there was repeatedly destroyed by raging floods.

The Byzantine Emperor Alexios I Komnenos is reported to have ordered the construction of a ship bridge during his battles with the Pechenegs around 1089. The Germans also used ship bridges more often. Under Emperor Frederick I it had become common for the emperors to cross the Adige on their way to the coronation in Rome not in Verona, but over a ship bridge outside the city walls.

In the centuries that followed, the mostly smaller armies at that time were able to find enough boats to cross rivers without bridges. It was not until the Spanish-Dutch War in the river-rich Netherlands that ship bridges became necessary again for the larger armies, such as the ship bridge built by the Spanish in 1579 over the Roer (German: Rur ), which was followed by a raft bridge over the Meuse . Alexander of Parma ( Alessandro Farnese ) had several ship and raft bridges built, for example during the siege of Maastricht , Ghent and in particular the ship bridge built over the Scheldt during the siege of Antwerp (1584–1585) , which was not intended to bridge the river but should close the siege ring and cut off supplies for Antwerp.

By the Thirty Years War , building ship and pontoon bridges had already become routine. All major rivers were crossed - often several times - by the various armies in this way. The bridges consisted of connected barges that were covered with planks. This enabled a stable transition for the artillery of the time. The bridges were completely dismantled for transport and carried with the army on 60 to 80 wagons. This required a lot of horses and a lot of logistical effort, especially when - as with the siege of Regensburg - two ship bridges were required to seal off the city.

The French under Louis XIV introduced a major innovation in 1672. The five-meter-long pontoons were now made of sheet copper that was attached to a wooden frame, and were therefore much lighter than the wooden boats. They were carried along with the associated standardized beams and boards on special horse-drawn vehicles. To cross larger rivers such as the Rhine, however, ship bridges were still preferred; the sheet metal pontoons were introduced into the imperial armies much later and hesitantly. Soon afterwards, the French introduced larger and more load-bearing pontoons for the transport of guns across large rivers. Some of the bridges reached considerable lengths, so the French built two bridges with 169 ships each over the Po in 1734 and the Russians built a bridge with 128 ships over the Dniepr in 1737 . At the beginning of the 18th century, the Chursachsen introduced fully locked pontoons made of sheet iron, the interior of which was sealed off several times. In 1746, longer and narrower pontoons were introduced that fit between the wheels of the wagon, so that its center of gravity was significantly lower and thus the frequent transport damage was reduced. Further improvements concerned a large number of smaller parts and the improvement of the driving characteristics of the wagons.

In the 18th and 19th centuries, numerous permanent ship bridges were built over wide and deep rivers, most of which existed until it became possible to cross such rivers with large steel truss bridges and at the same time to cope with the increased traffic loads. Not only did the traffic over the bridge play a role, but also the fact that pontoon bridges hindered navigation on the river itself. For civil pontoon bridges, there were only certain areas of application left, mainly when crossing inlets such as in the Seattle area and when crossing rivers that freeze over in winter such as in Siberia, where the low volume of traffic does not yet require very expensive fixed bridges to be built.

The military pontoon bridges have been further developed and now consist of large, hinged steel elements that are lowered into the water by trucks in a few moments and driven into the correct position with their own built-in drive.

Today's pontoon bridges

Europe

Rheindorf floating bridge
West India Quay Bridge

North America

Homer M. Hadley Memorial Bridge and
Lacey V. Murrow Memorial Bridge (front)

South America

Russia (Siberia)

  • Pontoon bridge at Tarko-Sale , a town in the Yamal-Nenets Autonomous Okrug on the Pjakupur River , replaced by an ice road in winter;
  • Pontoon bridges over the Pur , a river that flows into the Kara Sea in western Siberia (there are only pontoon bridges over the Pur, e.g. at Urengoy , in winter they are replaced by ice roads);
  • Pontoon bridge in the middle reaches of the Aiwassedapur , the right source river of the Pur, about 70 kilometers south of Tarko-Sale above the confluence of the Charampur, over which a road leads to the drilling camps east of the Aiwassedapur, such as Charampur and Wojenga;
  • Pontoon bridge at Nadym in the Yamal-Nenets (Ob-Busen) autonomous district over the Nadym (river) , which is replaced by an ice road in winter;
  • Pontoon bridge near Islutschinsk , Autonomous Okrug of the Khanty and Mansi / Ugra over the Wach , possibly replaced by the permanent bridge under construction in 2009.

China

Rest of the world

Floating bridge over the Österdalälven in Gagnef

Former permanent pontoon bridges

Ship bridges over the Rhine

Ship bridge, view from the Rhine station in Oberkassel to Düsseldorf , engraving around 1850
Ship bridge in Coblenz around 1896
Mülheim ship bridge around 1888 (former Mainz ship bridge ), with an open middle section to the ship passage

In 1853 there were several flying bridges , ship bridges and a steam ferry on the Rhine downstream from Basel . The following ship bridges existed:

In order to improve the traffic connection between Alsace and the Grand Duchy of Baden , nine ship bridges were built on the Upper Rhine in 1872/73 in the section between Weil am Rhein and Maxau . Most of the bridges existed until the end of World War II . The structures for road traffic connected at that time

Selection of other former pontoon bridges

Rzhev on the Volga, color photo by Sergei Mikhailovich Prokudin-Gorskii (between 1904 and 1916)

Pontoon bridges after permanent bridges were destroyed in the war

Pontoon bridge over the Danube, Novi Sad , Serbia

In addition to bridges destroyed in the Second World War, pontoon bridges were temporarily built in several places until the first post-war years.

Air strikes by NATO in 1999 destroyed the three bridges over the Danube in the city of Novi Sad in Serbia. Until the last bridge was rebuilt in 2005, a pontoon bridge was used to handle the traffic.

Web links

Commons : Pontoon Bridges  - Album with pictures, videos and audio files
Wiktionary: Pontoon bridge  - explanations of meanings, word origins, synonyms, translations
Wiktionary: Schiffbrücke  - explanations of meanings, word origins, synonyms, translations
Wiktionary: Schiffsbrücke  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ↑ The Great Brockhaus, 15th edition. Leipzig 1929
  2. ↑ Herodotus 4.83-87
  3. ↑ Herodotus 4.88
  4. ↑ Herodotus 4.89
  5. ↑ Herodotus 7.25-7.56
  6. ↑ Herodotus 7:21 and 7.25
  7. ^ The Bridge of Zeugma , School of Humanities, The University of Western Australia
  8. ↑ Suetonius, 19
  9. ↑ The distance between the places, often given as more than five kilometers, is around four kilometers; the bay is just over 20 m deep along the way.
  10. ^ A b c Johann G. von Hoyer: Handbuch der Pontonnier-Wissenschaften with the intention of their application for field use , Volume 1, 2nd edition. Publisher by Johann Ambrosius Barth, Leipzig 1830; Digitized on Google Books
  11. ↑ Peter Engerisser: A previously unknown view of the siege of Regensburg in 1634. In: Negotiations of the Historical Association for Upper Palatinate and Regensburg, Volume 148, 2008, pp. 55 ff., ISSN  0342-2518 .
  12. ↑ A bridge as a spring ambassador. In: www.thw.de. Retrieved July 23, 2016 .
  13. ↑ Zentralblatt der Bauverwaltung, February 25, 1893
  14. ↑ Rhine documents, collection of intergovernmental agreements, state implementing ordinances and other important documents about navigation on the Rhine since 1803