Clapper
Opening our list is an ancient form in which large flat stone slabs rest on piles of stones. Most of them were built in the Middle Ages to create a path across a river or other obstacle.
An excellent example of this type is the Postbridge, built over the East Dart River in the English county of Devon. Its slabs are more than 4 m long, and each slab weighs more than 8 tons. It was built in the 13th century to allow horses to cross the river, delivering tin to the famous town of Tavistock.
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Poetics and practice
There are 93 water arteries in St. Petersburg, this includes rivers, streams, canals and almost 100 reservoirs. Unhindered communication between the islands and parts of the city is ensured by bridges, of which there are about 800, of which 218 are intended for pedestrians. From the beginning of the construction of the city, a tradition was laid of the construction of bridges, without which St. Petersburg is no longer conceivable. They form part of its architecture, history, lore and culture.
Perhaps no other city in Russia uses divot crossings as actively as in St. Petersburg.
One of the oldest bridges, the Palace Bridge, is rightfully considered the symbol of the Northern capital. It was built according to the design of engineer Pshenitsky A.P. and connects Admiralteysky Island with the Spit of Vasilyevsky Island. State-of-the-art machinery lifts the 700-ton central span structure for ships to pass through.
The longest drawbridge in St. Petersburg is named after Alexander Nevsky. Its length is 905.7 m, the central opening span is made of metal, and the opening time of the structure is only 2 minutes.
Types of bridges in St. Petersburg include the entire history of bridge construction - from the first wooden ones to modern multi-lane cable-stayed structures. The Bolshoi Obukhovsky Bridge, for example, has a length of 2824 m, and today it is one of the longest engineering structures in Russia. It is made up of two parallel identical parts, along which four-lane one-way traffic is organized.
Truss
Instead of one beam having to withstand all the forces, a series of beams and trusses are used. A truss is a triangular frame that distributes tensile and compressive forces across the bridge.
There are several ways to build a truss bridge, but they all have the same goal: to distribute tension and compression forces so that the structure does not collapse. The truss gives stability to the entire structure, capable of withstanding large external loads over a long span.
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Pontoon
“Floating” crossings do not have a rigid frame and no connection with the shore. Their design is assembled from separate sections with a movable joint. A variation of this type of bridges are floating crossings. Most often, they are temporary structures that are used until ice is established on water barriers. They are dangerous during periods of strong roughness on the water, they make navigation difficult, and movement along them has restrictions for multi-ton trucks.
Arched
They began to be built in ancient times, and they remained popular until the industrial revolution and materials science allowed architects to create more advanced and efficient structures.
The underside of an arch bridge looks different than other types. All have a curved bottom that looks like someone cut a semicircle out of the bottom. Often such structures can be found within cities above small rivers, but also more massive ones above large rivers.
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Lunar
One of the most romantic types. The semicircular arch, reflected in the water, completes a 360-degree circle and resembles a full moon. These structures originated in Asian culture. They were originally built in China and then brought to Japan.
Mainly made of stone, wood and metal. Because they are steep, they have the advantage of not using up space from adjacent fields. This is a great way to encourage pedestrian traffic above the structure and boat traffic underneath it.
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Mobile
Some of the most technologically sophisticated bridges are moved to accommodate boats and barges. It can be vertical lifting, lifting, rotating or transport.
They are driven by electric motors, whether hydraulic pistons, work winches or gears. In general they can be quite long. The main disadvantage is that road traffic must be stopped when it is open to water traffic.
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Underlined ribbon
A tensioned ribbon bridge, also called a chain bridge, is a tension structure. It has two or more suspension cables built into the deck. These cables follow the arc of the catenary between the supports and provide rigidity.
The structure is usually made of concrete reinforced with steel tension cables. These bridges are very aesthetic, economical, and require virtually no maintenance. According to the editors of TopCafe, these are some of the most beautiful bridges in the world.
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From box beams
Photograph: Scott Davis, CC BY-SA 3.0, via Wikimedia Commons
The main beams consist of hollow box beams. The box beam is made from structural steel, prestressed concrete, or reinforced concrete and steel.
The box is usually trapezoidal or rectangular in cross section. This reduces the thickness of the slab, and therefore the weight of the entire structure. These bridges are mainly used for highway interchanges and modern elevated light rail structures.
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Segmental
Unlike traditional construction methods, which build structures in large sections, segmental construction is built from small pieces called segments.
They consist of concrete parts that are either built elsewhere and transported to the construction site, or constructed entirely on site. Although this type of construction is very economical for long spans, it requires high-tech machinery and special safety precautions during construction.
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Metal bridges
Most modern bridges involve the use of metal in the load-bearing parts of the structures. For quite a long time, a metal bridge was considered the most durable type of structure. Today, this material is an important, but not the only component of bridge connections.
Types of metal bridges:
- Arched structures.
- Viaducts with spans.
- Hanging, cable-stayed.
- Overpasses with supports made of reinforced concrete, where the spans are assembled from metal connections.
Metal structures have the advantage of being easy to assemble, which is why almost all types of railway bridges are built from this material. The metal parts are industrially manufactured in a factory and the size can be adjusted. Depending on the load-carrying capacity of the mechanisms with which the installation will be carried out, factory blanks for the future one-piece connection are formed.
The structure can be welded from parts directly at the final installation site. And if previously it was necessary to connect many parts of one span, now a crane with a lifting capacity of 3600 tons can easily carry and hoist an all-metal span onto supports.
Viaduct
The viaduct consists of a series of small spans between tall towers. Its purpose is to carry a road or railway through a valley or wetland. Although they are much more cost-effective than long-span bridges or tunnels, they usually lack vertical and horizontal clearance for large vessels.
Those built over water use successive arches or islands. They are usually connected to tunnels or other types of bridges to cross navigable waters in the form of viaduct sections.
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Cantilevered
Constructed using cantilevers, structural members that run horizontally and are supported at only one end. For small pedestrian bridges, the cantilever can be simple beams.
Cantilevers are useful for blocking a waterway without dividing it with river piers. They are mainly used for pedestrians, cars and trains. The longest cantilever bridge in the world is the Canadian Pont de Quebec, built in 1917.
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Suspension
In suspension bridges, the cables supporting the deck are suspended vertically (called hangers) from the main cable. This main cable is secured at both ends because any load applied to the structure is converted into a tension force.
A suspension bridge requires less materials to construct and longer spans can be achieved compared to other bridge types. This type is best able to withstand earthquakes.
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Latest innovations in the construction of artificial structures on highways
When creating artificial structures, designers try to apply progressive designs and use advanced techniques for performing such work. The main goal is to increase the reliability of the structure, reduce material consumption and reduce construction time. The objects being created must use standard solutions and prefabricated structures that meet current standards and technical specifications.
Recently, 3D printing of various designs has been gaining popularity. Plastic, steel, aluminum, chromium-cobalt, nickel and others can be used as starting materials. Special preparation of the powder is possible. So far, such technologies are used only abroad for the construction of small facilities. For example, on July 15, 2022, a steel bridge made entirely on a 3D printer was opened in Amsterdam. It united two embankments, weighs 6 tons and is 12 m long.
In Russia, work is underway to solve the problems of artificial structures, many of which (over 5,500) are in disrepair. Taking this into account, by 2024 it is planned to allocate more than 200 billion rubles to bring existing facilities to normal condition. Particular attention is paid to regulation and standardization in this area.
Cable-stayed
Cable-stayed bridges have become widespread since the 19th century. They consist of one or more columns (or towers) with cables directly supporting the deck. Columns absorb and cope with compression forces.
Unlike overhead, this type has cables that run straight from the tower to the deck, forming a series of parallel lines or a fan-shaped pattern. In this range, the cable-stayed bridge remains economical and elegant due to the relatively shallow beam depth.
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Beam
During construction, they use steel or concrete beams. The beam is the main horizontal support that supports the smaller beams on the deck. Girder bridges have come a long way from their limited short-span applications to a cost-effective functional form, becoming one of the most widely used bridge types. Now these types use modern, more durable materials.
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St. Petersburg legends
There are an abundance of different types of bridges in St. Petersburg, there are also ancient ones that have become symbols of a bygone era, but their purpose has not changed, although they have acquired a flair of stories and romance. Thus, the Kiss Bridge across the Moika River attracts tourists with its name, but it comes from the name of the merchant Potseluyev, whose drinking house “Kiss” was located next to the crossing, and the name has nothing to do with romantic impulses.
The Liteiny Bridge has become overgrown with interesting legends, and the dramatic plot arose immediately upon its foundation. It is believed that one of the foundation stones of the supports was the Atakan sacrificial stone. Now he makes passers-by sad and provokes suicides. To appease the “bloody” boulder, some townspeople throw coins from the bridge into the Neva and pour red wine. Also, many claim that you can meet the ghost of Lenin at Liteiny.
Overpass
The crosspiece consists of several short spans supported by closely spaced frames. The trestle, which is used as a bridge support, is a rigid frame made of wood or iron.
Iron and wooden trestles were widely used throughout the world in the 19th century. Although these bridges are largely obsolete, they are still invaluable to infrastructure transportation systems. For example, steel or wood trestles are often constructed in areas where a buried bridge could block potential flood waters.
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That we should build a bridge. British Army Pontoon Bridges and Ferries
This article will focus on floating and pontoon bridges.
But first, let's figure out what a floating bridge is, and what a pontoon bridge is, and what is its main difference from a floating one.
Floating bridge
is a bridge assembled to overcome a water barrier (river, lake, strait, etc.).
This bridge consists of two main parts.
The first is a floating bridge support: a boat or pontoon.
The second part is the decking or roadway, which is attached to the top of the boat (pontoon).
A type of floating bridge is a pontoon bridge.
. It is a structure in which a pontoon boat and a roadway are pre-connected into one whole. This connection constitutes a link in the bridge. When assembling a pontoon bridge, these links are connected to each other, assembling a passage over a water barrier.
Thus, a pontoon bridge is an improved version of a floating bridge.
An example of a floating bridge near Omsk. The floating supports made of barrels and the structure of the roadway made of planks are clearly visible
Ferry-bridge section of the PMP pontoon park. Here the floating support and the roadway form one whole, unlike the floating bridge design in the photo above
In our environment, the term “pontoon bridge” is more common. Therefore, in further presentation we will use this particular phrase more often.
So, in its simplest form, a pontoon bridge is a collection of shallow-draft boats attached to each other and set across a river or canal, with some kind of walkway or deck tied to the top.
Water acts as a support, so the lifting capacity limit is determined by the general and point buoyancy of the pontoons or boats.
The reality of pontoon bridges is that they have not advanced much in terms of their design since then.
Of course, there have been improvements in materials, methods of securing pontoons, decking materials, etc. All of this has resulted in increased lifting capacity, the ability to withstand fast river flows and high deployment speeds, but the basic principles have remained the same.
An even older version of the pontoon bridge is the river ferry. A simple, non-motorized, flat-bottomed boat that is towed across water using human, animal, or engine power.
A pontoon bridge will generally have a much higher capacity than a ferry, but the ferry has the distinct advantage of not blocking the river or channel to other vessels. On fast flowing rivers and rivers with high tidal levels, a pontoon bridge can also suffer without a serious shore anchorage system and constant attention from the bridge builders.
Pontoon bridges and ferries now often share common components. For example, the English Bailey Pontoon used many of the details of the Bailey Bridge, and the modern Air Portable Ferry Bridge can be used as a bridge, pontoon or ferry.
Therefore, it is sometimes difficult to separate the development of pontoon bridges and ferries because they are interrelated.
An example of a river ferry that is transported by a boat with a motor
Elements of the Air Portable Ferry bridge used as a ferry
The first pontoon bridges
Most historians believe that the first pontoon bridges were created and began to be used in China several hundred years BC.
They were commonly called boat bridges or pontoon bridges. Texts from the ancient book “Shi Jing” indicate that the first pontoon crossing in history was built in the 11th century BC. However, historian Joseph Needham, relying on more reliable sources, says that Chinese temporary pontoon bridges became common only during the 8th and 9th centuries BC.
The first more permanent and reliable pontoon bridges, connected by iron chains, appear during the Qin Dynasty between 221 and 207 AD. BC. Joseph Needham describes them as boats arranged in a row with planks laid across the boats, which is generally the same as the design of a pontoon bridge today. He also points out that Qing dynasty engineers improved pontoon bridges by developing more secure anchorages between boats and the roadway for permanent use.
An excellent example of such work by Chinese engineers is the Dongjin Bridge in Ganzhou, which was built during the Song Dynasty (960 to 1279 AD).
Modern version of the Dongjin Pontoon Bridge of the Chinese Song Dynasty
In Europe, an example of such bridges can be considered the pontoon bridges of the ancient Persians and Romans.
The most famous story is about a 2 km long pontoon bridge across the Bosphorus Strait, which was built in 493 BC. e. a Greek engineer for the Persian emperor Darius so that he could pursue the retreating Scythians.
Darius Pontoon Bridge
A little later, in 480 BC. BC, for Xerxes the Great of Persia, a large pontoon bridge was built across the Hellespont, or Dardanelles in modern terminology, which separated Asia from Europe. The first two bridges were made of papyrus and linen. It is therefore not surprising that they were destroyed during the storm. Xerxes reacted quite reasonably to this sad event at that time: he beheaded the engineers, ordered the water to be flogged and the construction of new bridges to begin.
First Xerxes Bridge
Later pontoon bridges (there were two of them) were stronger. As the Greek historian Herodotus wrote, they were built from more than 700 ships (approximately 360 ships per bridge), connected to each other by ropes. In addition, the ships, so as not to be scattered by a storm again, were installed on very heavy anchors.
In the first version of the bridge, anchors were only on the outermost coastal ships. After the ships were installed, boards covered with a layer of brushwood and earth were installed on top of them, forming a roadway. A fence made of branches was also installed on the sides of the roadway to prevent animals from panicking at the sight of the water surrounding them. The crossing of Xerxes' army took seven days and nights. At the same time, the army used the northeast bridge, and a huge number of servants and pack animals crossed through the southwest bridge.
Construction of the second bridge by the Persians
Xerxes' army crossing the second pontoon bridge
Alexander the Great sometimes carried ships with his army, divided into parts, which were assembled together when they reached the river bank, as when crossing the Hydaspes. The practice of using skins for inflation when troops had to cross a river was adopted by the Greeks, Romans and Mongols.
Assyrian soldiers used bags filled with air to cross rivers
Crossing Hannibal's troops on rafts across the river
The Romans were also great military engineers, and many of their military installations still stand today.
During the First Dacian War in 102 AD, Roman engineers built a large pontoon bridge over the Danube. The structure of the bridge, like its predecessors, consisted of connected boats and a plank deck.
Roman pontoon bridge over the Danube
A few years later, this event was overshadowed by the construction of another famous stone bridge, Trajan's, which was 1,135 m long. For more than a thousand years, this bridge was the longest arch bridge in the world.
Reconstruction of Trajan's Bridge over the lower Danube, carried out by engineer E. Duperrex in 1907
Pontoon bridges began to be used more widely in the 17th century.
During this time, pontoons were used as regular components of army trains: the Germans used leather, the Dutch used tin, and the French used copper "hide" on strong wooden frames.
In the mid-18th century, the Russians invented a collapsible pontoon, consisting of canvas fabric stretched over a wooden frame. For transportation, the frame was made collapsible, and the tarpaulin was folded. This was the pontoon park of Andrei Nemoy.
General view of the bridge from A. Nemoy Park
Drawing of a canvas pontoon from the book by A. Nemoy “Guide to the knowledge of marching bridges”, 1781
Great Britain
Now let's move on to English bridges.
One of the first examples of military bridging in Britain was King Edward I's attempt to cross the Menai Strait in Wales. Although this attempt was technically successful, tactically it turned out to be a failed operation.
In 1277, to suppress a Welsh rebellion, King Edward I sent a force of 2,000 soldiers to capture Fr. Anglesey, thereby depriving the opposing forces of most of their food supplies and outflanking the defending forces at Conwy.
To overcome the strait, the caretaker of the Cinque ports (Stephen de Pencaster) was tasked with building a pontoon bridge. For this work he used carpenters and shipwrights from his area. In terms of design, the new bridge was no different from all previous ones. It also consisted of several interconnected boats and a roadway made of log decking. This structure was called the “boat bridge”.
Unfortunately, the bridge elements were too heavy to transport. Therefore, it was decided to build a bridge in Chester, closer to the territory of the rebels.
Stephen de Pencaster Boat Bridge
Despite the fact that the bridge was in perfect order, poor communication and coordination played a negative role. As a result, British troops crossed the strait at the most inopportune moment and found themselves caught between the rising tide and the opposing forces. All this led to a disastrous result.
This is how Walter of Guisborough described it in his chronicle:
“When they reached the foot of the mountain and after some time came to a place some distance from the bridge, the tide came in with a great flood, so that they could not return to the bridge because of the great water. The Welsh came from the high mountains and attacked them, and in fear and trembling because of the great number of the enemy our people preferred to face the sea rather than the enemy. They entered the sea, but, heavily loaded with weapons, drowned instantly.”
Edward also used military bridge builders in Scotland, this time more effectively. The King commissioned military engineer Master Richard to create a set of portable bridges at King's Lynn in Norfolk. It was decided to use the bottom bridges in the future to cross the Forth River, carefully bypassing the well-protected stone Stirling Bridge.
The next stage in the use of pontoon bridges dates back to the beginning of the 19th century.
There are fragmentary accounts of the use of a number of improvised pontoon bridges in India by General Sir Arthur Wellesley early in the century, but without specific examples.
English pontoon bridge across the river. Indus
In 1809, during the Napoleonic Wars in Spain, Lord Wellington ordered the destruction of a stone bridge over the Alcantara River to prevent French freedom of movement. Although the explosion initially did not completely destroy the bridge, after some time one arch collapsed on local residents. This left a negative impression on the military, especially since it was an operation led by British forces.
When the tide of the war changed, in April 1812 Wellington ordered Lieutenant Colonel Sturgeon to repair the previously destroyed bridge or build a pontoon bridge. Sturgeon was not an officer in the Corps of Engineers, but an officer on the Royal Staff. According to his plan, a suspension bridge over the destroyed arch was the best option. Construction took place away from the bridge site, and its elements were transported by wagons. After the ropes were stretched across the span in place, the rolled bridge was unrolled and secured to them.
This is how the episode is described on the Napoleon Series website by General Leith Hay, commander of the 5th Division:
“The destroyed arch had such a long span and the bridge parapet was so high from the river bed that repairs using timber were impossible. The passage to be crossed was ninety feet (27 m) wide, and the height of the bridge one hundred and eighty feet (54 m) from the bed of the river... The work was begun by installing two beams on supports four feet (1.2 m) high and ninety feet apart. They were attached to the side and end walls of the building with staples and slings to prevent them from moving closer together due to the tension of the ropes. Then 18 cables were stretched around them, running from one end to the other. Eight pieces of wood, six inches square, were placed on the ropes at equal distances, with notches one foot apart cut into their surfaces to secure them; These recesses were burned with a hot iron so that the ropes did not rub. The cables were then tied to the beams; these were tied together with rope yarn, and the sleeper chains were screwed and laid on the net, and attached to two beams originally placed at the ends of the work. The boards were cut and prepared for laying crosswise, drilled at the ends to create a line designed to secure them to the sleepers and to each other... The next stage was to prepare the edge of the broken part of the bridge and cut channels in the masonry to receive purchases. When they arrived on the spot, four strong cables were stretched from side to side as conductors for the passage of the cable-stayed bridge, the beam on the south side having been previously sunk into the masonry; then the whole thing was pulled out by a winch installed on the opposite pier.”
To understand the importance of this moment and the subsequent destruction of the French pontoon bridge across the river. Tagus at Almaraz, it must be said that these two actions reduced the march distance for Wellington's troops by 250 km and added 650 km for the French.
Model of Lieutenant Colonel Sturgeon's Alcantara Bridge
Also in 1812, significant efforts were made to build bridges across the Tagus River. But all efforts ended with the construction of a stone bridge more than 190 m long.
When Wellington won in Spain, he moved to France.
To block the French army on its way to Toulouse, it was necessary to cross the Adour River. The choice of crossing point was complicated by the presence of French garrison forces, so to provide some protection for the crossing, a place downstream was chosen, but this meant that the river was wider here (almost 275 m), and the bank was subject to strong tidal fluctuations.
The solution to this important task was entrusted to two officers of the engineering troops - Lieutenant Colonel Elphinstone and Lieutenant Colonel Burgoyne, as well as the well-known Lieutenant Colonel Sturgeon, who represented the Royal Service Corps. Lieutenant Colonel Burgoyne was later promoted to Field Marshal and, incidentally, one of the buildings (the Burgoyne Study Center) at the Royal School of Engineering in Chatham is named after him.
Due to the large width of the barrier and the strong tidal fluctuations, it was obvious that a conventional pontoon or suspension bridge would not be suitable for the job. Therefore, military engineers decided to use local coastal vessels called chasse matrees.
These were large boats, some of which exceeded 15 meters in length. 48 boats were “rented”. The plan developed by the lieutenant colonels provided for the mooring of boats with a bridge surface consisting of wooden planks at a distance of 10 to 12 meters. Because of the large quantities of timber that would be required, Lieutenant Colonel Sturgeon proposed a technique similar to that which he had used in the construction of his bridge over the Tagus in Spain, that is, the use of ropes to provide a surface on which fewer planks could be placed.
The cables were extended to the shore from the two central boats and secured with weights (18-pounder guns) and capstans anchored in the ground. To keep the boats on the water, each of them had its own anchor, and some had two anchors.
Due to the fast flow of the river, this was more difficult to do than suggested. It took a lot of effort to install the bridge, but it was worth it. Only 34 boats were delivered to the bridge construction site. The rest were lost due to bad weather and tide. A few days before the construction of the crossing began, a bridgehead was captured on the opposite bank. Its defenders had to repel several French attacks.
The bridge was quickly completed overnight, and by noon the next day troops, wagons and artillery were transferred across it.
Historian Napier said of the bridge:
“A monumental undertaking that should always rank among the wonders of war.”
Construction of a floating bridge across the river. Adur
The Duke of Wellington took a keen interest in military bridging and was fully aware of the strategic advantages it could provide. Therefore, much more attention began to be paid to this subject.
Permanent bridge trains were introduced and the structure of the Royal Engineers in the Corps of Royal War Masters was created. In 1812 a permanent training center was established at Chatham to train the Corps of War Masters (later the Corps of Sappers and Miners) and Royal Engineers.
During the Peninsular War, Wellington also realized that bridge equipment needed to be highly mobile, so he ordered some of the horses from the artillery train to be removed and given to the engineers.
In his dispatches he wrote:
“We are unfortunately delayed due to the movement of our bridge, without which it is obvious that we cannot do anything, the equipment is quite new and only comes from Abrantes, but there have already been many breakdowns and I understand that the carriages are terribly bad. I will have the sad work of this bridge throughout the campaign, and yet we can do nothing without it.”
Transportation of pontoons by bridge train. 20th century postcard
The end of the Napoleonic Wars ushered in almost 50 years of peace in Europe. But British forces continued to be used abroad, for example in India.
In 1839, during the offensive against Afghanistan, a pontoon bridge with a very large span was built at Bukkur (now Pakistan).
Bukkur is a fortified island and a natural passage on the banks of the Indus between Sukkur and Itore. The bridge itself consisted of two spans, one 200 m long and the other more than 300 m long. The construction of this bridge took more than 90 boats and 14 days. Although the high speed of the river and its rocky banks created problems, the bridge allowed several thousand soldiers and dozens of pieces of equipment to be transferred across it.
Bridges continued to play an important role throughout the 19th century during hostilities in Abyssinia, Crimea, India, West and South Africa.
The early open pontoons had a number of disadvantages, the biggest being the difficulty of transporting them to site (if not by river) and their susceptibility to bad weather. Therefore, in the early 1800s, a concerted effort was made to improve bridge design.
In 1814, Colonel Sir James Colleton (otherwise known as Colleton) designed a cylindrical pontoon buoy with conical ends and made of wooden staves like a barrel. This invention, unfortunately, was not successful. But the closed pontoon became the basis for later types.
The first significant development after this was the Pasley pontoon of 1817, designed by Lieutenant Colonel Charles Pasley of the Engineering Establishment at Chatham. Pasley's pontoon differed from open boats in a number of key ways. It was enclosed and therefore had greater resistance to flooding, had many fastening points for attaching the road deck and, perhaps more importantly, was sectional - consisting of two parts.
The bow of each part of the pontoon was pointed, and the stern was square-shaped. This made it possible to split the pontoon, as indicated above, into two parts (half-pontoons) for easier transportation. When the bridge was assembled, a pair of these pontoons were connected stern-on to form a single float (single support), both ends of which were pointed, an important consideration for use on water obstacles.
The pontoons were built from lightweight wooden frames covered with copper sheets and clad in wood. Each half-pontoon was divided into waterproof compartments and equipped with means of pumping out water. To transport the bridge, a pair of half-pontoons and the superstructure of one bridge span were loaded onto one trolley.
Sir Charles Pasley
And his pontoon
The Pasley pontoon served for many years, but was replaced in 1836 by the Blanchard pontoon, which was cylindrical with parabolic ends, consisting of tin cylinders 3 feet (0.9 m) wide and 22 feet (6.6 m) long, spaced 11 feet (3.3 m) apart, making the pontoon very buoyant. Two pontoons and two superstructure compartments were transported on one trolley.
With one or two modifications, Blanchard pontoons were used by the British Army until the late 1870s, but were eventually abandoned.
Blanchard pontoon model
In the late 70s of the 19th century, British engineers returned to the open pontoon design, which was followed by engineers of all continental armies at that time.
Blanchard's pontoon was followed by a pontoon designed by Colonel Binden Blood.
The pontoon was named Blood, in honor of its creator. Its design, as noted above, returned to the concept of an open boat with decked ends and partially decked sides on which oarlocks were attached. The sides and bottom were of thin yellow pine with canvas attached to both surfaces with Indian gum mortar and coated on the outside with marine glue.
General Sir Binden Blood
In his memoir, Four Score Years and Ten, published in 1935, Binden writes:
“In 1865, I was appointed to one of the detachments of the Royal Engineers, whose specialty was transportation and the rapid construction of floating bridges on the First Line. In November 1866 I moved to Chatham with this detachment. We spent an instructive and very pleasant year there, returning to Aldershot in November 1867. While my party was at Chatham in the summer of 1867, our superior authorities decided that our equipment for a pontoon bridge was unsatisfactory in some details, and invited the officers to submit designs for a new sample. So I submitted a new design, which was approved for trial, and some time after my detachment returned to Aldershot in November 1867, I was sent back to Chatham to carry out the necessary production and experiments by order of the RE Committee, which then dealt with such questions. I remained at Chatham, with a short visit to Aldershot in 1870, until I went to India in 1871, and the new pontoon equipment was finally accepted for supply in 1870.”
Binden Blood's pontoon in transport position
Already in India in June 1879, Binden Blood personally supervised the construction of his own bridge at Fort Pierce, which was supposed to replace the ferry that had been operating there for about 9 years, operating on a cable stretching from coast to coast.
The length of the Blood pontoon bridge was about 250 m.
It must be said here that the future British Prime Minister Winston Churchill served under the command of Binden Blood in the Malakand Field Forces.
It is also important to note the fact that Queen Victoria herself showed interest in the Blood pontoon bridge. She was directly present at the construction of the 240-foot (72 m) bridge over the Thames at Datchet near Windsor. She apparently found the event interesting, for the next day the Queen appeared at the bridge again to witness its removal from the water barrier.
We find a description of the Blood pontoon (or in the literal translation of the “Bloody Pontoon”) in the “Treatise on Military Carriages and Other Products of the Royal Crew”:
“The pontoon can be used as a bridge pontoon or as a boat: its exterior dimensions are 21' 1" x 5' 1" x 2' 6.5" deep; its weight is 7 cwt per pound, and its tonnage is 9.685 tons. In horizontal section it is rectangular, its sides are almost straight and vertical, and the ends are rounded. The frame, which is very light, is made of yellow wicker and elm, the straight parts being made of the former, and the curved parts of the latter. The frame is clad in yellow pine and each side of the clapboard is covered with a canvas attached with Indian rubber mortar. Before painting, the pontoon canvas is coated with marine glue, and the bottom is protected by four longitudinal stiffeners covered with iron friction plates. The pontoon has eight wooden handles on the sides, about halfway up, six attached with ropes and two with wires. Moreover, the latter serve as eyes for fastening the cables, it also has a ring at each end for the cable and is equipped with four oarlocks along the gunwale on each side and at each end one for the steering oar; there are also provisions for attaching the saddle beam.”
In this situation, a natural question arises.
Why, having advanced closed pontoons, did they still return to the open boat design?
At the time, the answer turned out to be very simple.
Experience with tubular or round structures such as Blanchard pontoons has shown that when submerged more than halfway, they become unstable and difficult to handle. So one idea to counteract this was to make the pontoons triangular in shape. That is, tapered towards the bottom, like those of ships.
This shape was necessary so that when pressure from passing loads is applied, a larger volume is immersed, and this forms a more stable and increasing counterforce. The idea was good, but impractical with the construction techniques of the time. Therefore, it was decided to return to the design of a conventional open boat. In fact, numerous European armies, especially the Dutch and French, given their considerable experience with pontoons, never used the British method of enclosed pontoons. Clearly this was a case of experience winning over new designs.
The “Bloody Pontoon” indeed had a number of important features. For example, a longitudinal support beam was installed on the pontoon to take the load from the deck. This beam could easily be removed if the pontoon were used as a regular boat.
Around this time, the Royal Engineers, like many European armies, formed a special pontoon force.
These troops were manned by tall and physically strong soldiers because they had to physically lift the heavy pontoon equipment. These specially created units performed well in the South African wars and, thanks to their physically strong fighters, won no less than thirteen championships in tug-of-war between units of the British army!
A further development of the Blood pontoon was the Mark II pontoon or Clauson pontoon, which was destined to remain in service until 1924.
Clauson pontoon drawing
The pontoon is named after Royal Engineers Lieutenant J. E. Clauson.
This weapon element was, in fact, a modified “Bloody Pontoon”, divided in half. It also demonstrated a return to the multi-section design previously proposed in the Pasley pontoon and the highly successful Austrian Birago pontoon.
Drawing of Clauson's pontoon
Royal Engineers pontoon unit on the march with a Clauson or Mark II pontoon - 1915
Instead of two identical sections, Clauson's pontoon used a pointed bow and square stern configuration. These two sections could be used independently of each other if necessary. The parts of the pontoon were connected together using phosphor bronze fittings. This flexibility in use allowed the assembly of a diverse range of bridge configurations, from light infantry bridges to heavier van and vehicle types.
The photographs below show the Mk II pontoon bridge in action during the First World War.
A British artillery battery crosses a pontoon bridge over the Diyala River near Baghdad in March 1917. This bridge was built by the 71st Field Company, Royal Engineers, at 11am on 10 March after a night crossing of the river by the 5th Battalion, Wiltshire Regiment. The 88th Field Company, the Royal Engineers and the 8th Welsh Pioneers provided a bridgehead on the Turkish-held side of the river (photo from remuseum.org.uk)
D Company, 1st Battalion "Cameronians" (Scottish Fusiliers) crossing the pontoon bridge over the Marne at La Ferté-sous-Jouare, 10 September 1914 (photo from remuseum.org.uk)
Very often, when arranging a pontoon crossing, we encountered the problem of connecting the bridge to the shore. This is especially important if the bank is higher than the road deck or the river is tidal. Some arrangements are required here to provide access from the river bank to the pontoon bridge deck.
The British solved this problem simply.
They used the experience of the Austrian army, where they used the Birago overpass to cross from the shore to the bridge and back.
Trestle (goat) Birago - an invention of the Austrian military engineer Karl von Birago, one of the types of fixed supports for pontoon bridges
The video below shows an Austrian army training exercise in 1939. In them, military engineers are setting up a coastal crossing using an overpass that looks like a Birago goat! At the turn of the century, the Birago flyover was replaced by the Weldon flyover.
At the outbreak of the First World War, two Royal Engineers bridge trains were fitted with Mark II pontoons and Weldon trestles, as an addition to the range of light raft equipment derived from much earlier designs.
Drawing of the Weldon overpass
Weldon trestle and Mk II pontoons used on the Tigris River, 1917
Developments during the First World War included the introduction of the Marston Lever Trestle and the Mark IV trestle into pontoon bridges.
The video below shows Australian Anzacs building bridges across the Nile River in Egypt during the First World War. The footage clearly shows the Mark II pontoons and the Weldon Trestle, the bridge installation process, and the use of the pontoons as a ferry.
As the weight of vehicles and artillery increased, it became apparent that the floating bridges would need to be modernized to accommodate the changing conditions.
These developments included the Mark III pontoon, the Mark II with different cladding and the Mark V trestle, which remained in service until the 1920s.
A number of floating bridges were designed and used during the war, but in relatively small numbers, including the Type B Sankey Bridge, which used steel beams instead of timber beams on a Mark II Pontoon and a heavy steel pontoon.
The next major achievement of English military engineers was the Inglis Heavy Floating Bridge, unique at the time because it used a continuous girder design to distribute the load across a series of new heavy pontoons. Despite significant progress and successful trials in Christchurch, Dorset, the bridge was not adopted because the war had already ended.
Inglis Pontoon Bridge. Tank bridge trials at Christchurch, Dorset, late 1918
The Inglis heavy floating bridge being tested, 1918. Still from a film about the tests from the website www.iwm.org.uk
In the late twenties of the twentieth century, a number of new pontoons and trestles were introduced, including the Mark IV pontoons and the Mark V trestle, as the ferry equipment was updated.
The Mark IV pontoon was completely enclosed and consisted of Consuta plywood, so it was often called a Consuta pontoon. With safe buoyancy, the bridge's load capacity was 6.5 tons.
The figure below shows the method of making the pontoon hull skin.
The brass was a continuous stitch that looped in and out of the body through the wood lining. The Consuta has four veneers (overlays that replace the outer layer) of mahogany, laminated with calico (canvas impregnated with linseed oil) to ensure the skin is waterproof.
This design resulted in a very light but very durable body. Copper was used because there were no waterproof adhesives at that time. This form of stitched construction was patented by Saunders and the plywood was named Consuta plywood.
Pontoon Consuta. Drawing from the pontoon manual
The Mark V sawhorses were the first to use mild steel instead of wood.
The next Mark VI sawhorses were much more powerful and were introduced in 1929. Goats could be used without pontoons as extreme bases for crossing narrow obstacles.
A Morris Carrimore light truck of the 17th Field Company, Royal Engineers, towing a pontoon on a trailer.
The video below from Pathe shows the moment the Mark IV pontoon bridge was erected.
To be continued…
Cable-stayed with cantilever spar
A modern type of cable-stayed bridge. In such a design, the distribution of forces does not depend solely on the cantilever action of the spar (support tower). The weight distribution in the spar and the angle between the spar and the bridge play an important role in reducing the overturning forces applied to the base spar.
Sometimes the spar is raised to an angle where it is balanced by the structural tail. Many designs have a backward-curved spar that supports the weight of the deck.
Wooden bridges
The first bridges in human history were built from wood. For a long time, these structures could not be used without appropriate repairs, constant preventive maintenance and replacement of individual parts and fastenings. This was associated with construction difficulties and the fragility of the material itself. The following types of wooden bridges are currently being built:
- Depending on the system - beam, strut.
- Depending on the design - package buildings with spans, truss bridges.
The beam structure is the simplest, and therefore the most quickly assembled structure. The support beams are driven into the ground to a depth of 4 m. Nozzles are placed on the upper ends of the piles using steel pins, all piles are tied into a single whole, and a canvas for movement is laid on top. When building a wooden bridge, it is important to create a strong connection between the structure and the embankment of soil at both ends, this is done so that the bridge is stable.
Now there is a tendency to revive the construction of wooden bridges, which is associated with the advent of technology for manufacturing laminated veneer lumber, which is more resistant to aggressive environments, external torsional forces and is more durable in operation, moreover, its length does not depend on the natural growth of the tree.
Cable-stayed with side spar
A rather unusual bridge in which the cable support does not block the roadway. Instead, it cantilevers on one side. Cable runs are usually aligned along the centerline of the entire structure. Forces are transmitted through cable supports, then through compression supports and then into the foundation.
Such unusual engineering structures are suitable for regions where the road goes upstream, crosses a stream and turns back on the other side in a downstream direction. By building part of the turn on a structure, the turn can be smooth, allowing vehicles to move faster.
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Advantages of metal structures
Iron is rarely used as a material for bridge construction due to its poor corrosion resistance. High-strength steel and its compounds have become a popular material. Its excellent performance qualities can be assessed on projects such as cable-stayed bridges with huge spans. An example is the Moscow Bridge across the Dnieper in Kyiv or the Obukhovsky Bridge in St. Petersburg.
In the construction of railway bridges, metal structures with lattice trusses are widely used. The main advantage of these solutions is operational efficiency, speed of construction and dismantling of individual parts, relatively low production costs, and the ability to construct a structure in the shortest possible time on accessible sites and in any geographical area.
Spiral
Photo: Jakob Montrasio from Saarbrücken, Germany, CC BY 2.0, via Wikimedia Commons
This type of structure crosses its own path and is useful on steep slopes. The structure rises in a steady curve until it closes the loop, passing above itself as the height increases, allowing vehicles to gain altitude over a relatively short horizontal distance.
It is a better alternative to zig-zag roads to avoid stopping vehicles and changing direction when going up or down. The same design is typical for many multi-storey car parks.
Bridges are widely represented in the folklore of different peoples of the world. For example, in Russian fairy tales there is a Kalinov bridge thrown across the Smorodina River. It is believed that it connects the world of the living and the dead. In the Scandinavian sagas, there is a mysterious bifrost - a “trembling bridge” that connects the heavenly city of Astrad with other territories and worlds. The TopCafe editors ask you to add in the comments to the article what other types of bridges you would like to see here.
Classification of bridge structures
Types of bridges can be classified according to several criteria:
- according to the main purpose of use;
- constructive solution;
- building materials;
- depending on length;
- by service life;
- depending on the operating principle.
Since a man threw a tree from one bank of the river to get to the other, a lot of time has passed and a lot of effort has been put into the construction of engineering structures. As a result, different types of bridge designs emerged. Let's take a closer look at them.
