Pontoon bridge

A pontoon bridge (or ponton bridge), also known as a floating bridge, uses floats or shallow-draft boats to support a continuous deck for pedestrian and vehicle travel. The buoyancy of the supports limits the maximum load they can carry.The Chhun Chhiu Hou Chuan says that in the 58th year of the Zhou King Nan (257 BC), there was invented in the Qin State the floating bridge (fou chhiao) with which to cross rivers. But the Ta Ming ode in the Shih Ching (Book of Odes) says (of King Wen) that he 'joined boats and made of them a bridge' over the River Wei. Sun Yen comments that this shows that the boats were arranged in a row, like the beams (of a house) with boards laid (transversely) across them, which is just the same as the pontoon bridge of today. Tu Yu also thought this. ... Cheng Khang Chheng says that the Zhou people invented it and used it whenever they had occasion to do so, but the Qin people, to whom they handed it down, were the first to fasten it securely together (for permanent use).... composed of twenty three boats, of great excellence and strength attached together by a long chain of iron as thick as a man's thigh, and this was moored on each side to an iron post as thick as a man's waist extending a distance of ten cubits on the land and planted firmly in the ground, the boats being fastened to this chain by means of big hooks. There were placed big wooden planks over the boats so firmly and evenly that all the animals were made to pass over it without difficulty.and meanwhile other chief-constructors proceeded to make the bridges; and thus they made them: They put together fifty-oared galleys and triremes, three hundred and sixty to be under the bridge towards the Euxine Sea, and three hundred and fourteen to be under the other, the vessels lying in the direction of the stream of the Hellespont (though crosswise in respect to the Pontus), to support the tension of the ropes. They placed them together thus, and let down very large anchors, those on the one side towards the Pontus because of the winds which blow from within outwards, and on the other side, towards the West and the Egean, because of the South-East and South Winds. They left also an opening for a passage through, so that any who wished might be able to sail into the Pontus with small vessels, and also from the Pontus outwards. Having thus done, they proceeded to stretch tight the ropes, straining them with wooden windlasses, not now appointing the two kinds of rope to be used apart from one another, but assigning to each bridge two ropes of white flax and four of the papyrus ropes. The thickness and beauty of make was the same for both, but the flaxen ropes were heavier in proportion, and of this rope a cubit weighed one talent. When the passage was bridged over, they sawed up logs of wood, and making them equal in length to the breadth of the bridge they laid them above the stretched ropes, and having set them thus in order they again fastened them above. When this was done, they carried on brushwood, and having set the brushwood also in place, they carried on to it earth; and when they had stamped down the earth firmly, they built a barrier along on each side, so that the baggage-animals and horses might not be frightened by looking out over the sea.But the most commodious invention is that of the small boats hollowed out of one piece of timber and very light both by their make and the quality of the wood. The army always has a number of these boats upon carriages, together with a sufficient quantity of planks and iron nails. Thus with the help of cables to lash the boats together, a bridge is instantly constructed, which for the time has the solidity of a bridge of stone.Smaller, lighter pneumatic pontons piggy-backed upon large aluminum heavy pontons for combined transportPneumatic pontons support a treadway bridgePneumatic pontons being carried by heavy 6×6 transportsHeavy ponton bridge supported by large aluminum pontonsTreadway bridge atop pneumatic pontonsInfantry support bridge supported by light aluminum pontoonsTreadway being installed using truck mounted craneInfantry footbridge supported by pontonsTreadway style infantry support bridge built on light aluminum pontonsM2 Treadway bridge supported by pneumatic floatsBritish troops crossing the Seine at Vernon, France on 28 August 1944Heavy ponton bridgeBailey bridge supported by pontoonsGerman pioneers construct a pontoon bridge across the Dnieper during the battle of Kiev, September 1941German engineers building a pontoon bridge across the Prut River during the advance towards Uman, July 1941 A pontoon bridge (or ponton bridge), also known as a floating bridge, uses floats or shallow-draft boats to support a continuous deck for pedestrian and vehicle travel. The buoyancy of the supports limits the maximum load they can carry. Most pontoon bridges are temporary, used in wartime and civil emergencies. Permanent floating bridges are useful for sheltered water-crossings where it is not considered economically feasible to suspend a bridge from anchored piers. Such bridges can require a section that is elevated, or can be raised or removed, to allow waterborne traffic to pass. Pontoon bridges have been in use since ancient times and have been used to great advantage in many battles throughout history, among them the Battle of Garigliano, the Battle of Oudenarde, the crossing of the Rhine during World War II, and during the Iran–Iraq War Operation Dawn 8. A pontoon bridge is a collection of specialized, shallow draft boats or floats, connected together to cross a river or canal, with a track or deck attached on top. The water buoyancy supports the boats, limiting the maximum load to the total and point buoyancy of the pontoons or boats. The supporting boats or floats can be open or closed, temporary or permanent in installation, and made of rubber, metal, wood, or concrete. The decking may be temporary or permanent, and constructed out of wood, modular metal, or asphalt or concrete over a metal frame. The spelling 'ponton' in English dates from at least 1870. The use continued in references found in U.S. patents during the 1890s. It continued to be spelled in that fashion through World War II, when temporary floating bridges were used extensively throughout the European theatre. U.S. combat engineers commonly pronounced the word 'ponton' rather than 'pontoon' and U.S. military manuals spelled it using a single 'o'. The U.S. military differentiated between the bridge itself ('ponton') and the floats used to provide buoyancy ('pontoon'). The original word was derived from Old French ponton, from Latin ponto ('ferryboat'), from pons ('bridge'). When designing a pontoon bridge, the civil engineer must take into consideration the Archimedes' principle: Each pontoon can support a load equal to the mass of the water that it displaces. This load includes the mass of the bridge and the pontoon itself. If the maximum load of a bridge section is exceeded, one or more pontoons become submerged. Flexible connections have to allow for one section of the bridge to be weighted down more heavily than the other parts. The roadway across the pontoons should be relatively light, so as not to limit the carrying capacity of the pontoons. The connection of the bridge to shore requires the design of approaches that are not too steep, protect the bank from erosion and provide for movements of the bridge during (tidal) changes of the water level. Floating bridges were historically constructed using wood. Pontoons were formed by simply lashing several barrels together, by rafts of timbers, or by using boats. Each bridge section consisted of one or more pontoons, which were maneuvered into position and then anchored underwater or on land. The pontoons were linked together using wooden stringers called balks. The balks were covered by a series of cross planks called chesses to form the road surface, and the chesses were secured with side guard rails. A floating bridge can be built in a series of sections, starting from an anchored point on the shore. Modern pontoon bridges usually use pre-fabricated floating structures.