Bridges are engineering structures and they can come in a wide variety of shapes and have different purposes. Network, drawbridge, suspension, railway, automobile, pedestrian - these are all bridges.

Bridges are used to connect something or someone. The most common and ancient are bridges over rivers.

Everyone knows about the existence of drawbridges. Why are they needed? Why can't you build a regular bridge? This is due to the fact that a huge airliner cannot pass under a simple bridge in height, so drawbridges are built at shipping sites. They can diverge vertically (up) or horizontally (to the sides). The very first drawbridge was built over the River Thames.

The simplest type of bridge is a beam bridge. It serves to cover a small empty space. There are even dental bridges! Bridge teeth are a prosthesis that needs to be installed if several or one tooth is missing. A prerequisite is the presence of two teeth on the sides of the installation site. The metro bridge serves to carry a metro line across it.

Railroad bridges are designed specifically for trains. Pedestrian bridges can only be used by pedestrians. Cars cannot drive across them; there are separate road bridges for them. The very first bridge appeared in ancient times and was a simple log thrown over a narrow chasm. Later, these structures began to be built from stone.

Bridges were also used to provide water to the population. This type of structure is called aqueduct. Some bridges are architectural works of art, therefore they serve not only as a means of transportation, but also as a decoration of the city. A multifunctional bridge was built in Italy - in addition to its main function, it is planned to be used as a wind and solar power station in the future (Wind and Solar Bridge "Solar Wind").

In Denver, a bridge was created specifically for animals. It connects two parts of the forest that were separated by a highway. The longest bridge in the world was built in China and is 22 miles (35.41 km) long. It connects the shores of the ocean. This building is surprising in that it has a special service where you can refuel your car, eat and spend the night.

A compass is an indispensable thing on a serious hiking trip. With the help of this useful device, equipped with a magnetic needle, a traveler can choose the right direction of movement without fear of getting lost in an unfamiliar area. To prevent a compass from becoming a useless accessory, you need to know how to use it correctly.

What is a compass for?

People go out into nature quite often. For some, this is an opportunity to visit the forest in search of mushrooms and berries. Others love hiking in unexplored places. Untouched nature, fresh air, songs with a guitar by the fire and other attributes of romance, however, are good only when travelers feel confident in the forest. And for this you need to be able to navigate in unfamiliar places.

A person who is in a foreign city usually does not have problems with orientation. In a large metropolis it is quite easy to determine your location. Elements of city infrastructure, signs with the names of streets or metro stations, and other information signs will help the tourist with this. To feel confident, it is often enough to have the most general map of the city at hand.

It's another matter if you find yourself in nature. There are no usual attributes of civilization here, and most often there is no one to ask for directions. And then the compass comes to the rescue. It is precisely the device with which you can relatively easily navigate in a field, in the mountains or in a forest, that is, wherever the wind of wanderings has thrown you. This compact device, equipped with a circular scale and a magnetized pointer, allows a trained tourist to confidently determine the sides of the horizon and mark the correct direction of movement.

To put the compass in “combat readiness”, remove it from the lock and place it on a horizontal plane. At the same time, the magnetized arrow will be released and begin to oscillate, after which it will become motionless, pointing with the blue end to the north and the red end to the south. Now you need to turn the body of the device so that the zero on the dial coincides with the end of the arrow pointing north.

Please note that you need to start orienteering not at the moment when you find yourself in a hopeless situation and get lost, but at the moment you start moving through unfamiliar terrain. Knowing the location of the sides of the horizon at the moment you enter the forest, you can immediately understand in which direction you will move. Naturally, you will need to return in the opposite direction.

Using the marks on the compass dial, you can choose any direction of movement for yourself. In order not to get lost on a hike, you will only need to remember or write down the azimuth to a noticeable landmark marked on the map or clearly visible on the ground. Azimuth is the angle expressed in degrees between the direction to the north and the direction of your chosen object. This angle, which can range from 0 to 360 degrees, is measured in a clockwise direction.

If you change direction along the way, you should always measure the new azimuth with a compass, drawing a broken line on the map or traffic diagram. To master working with a compass and map, it is advisable to conduct one or two field lessons in an area with which you are relatively familiar. This skill, combined with a compass, will help you easily navigate where no one has gone before.

Everything interesting

A compass is a device with which you can determine the cardinal directions, remember your route and then exit in the right place. It is very useful, but only if you know how to use it. Learn how to use this device...

A compass is an indispensable thing on a serious hiking trip. With the help of this useful device, equipped with a magnetic needle, a traveler can choose the right direction of travel without fear of getting lost in an unfamiliar…

Bridges perform not only a practical task, that is, they allow a person to cross from one bank to another, but also an aesthetic one - they can be a decoration of a city or area. That's why architects try to make bridges beautiful, and sometimes...

A water bridge is a structure designed to cross water bodies by shipping vehicles. A body of water means a river or an artificial canal. A water bridge cannot cross railway or road tracks, as it is more economically beneficial...

In order to move using a compass, you need to determine the azimuth from the map. This is relevant for aircraft and ships making long flights and voyages. This is also true for hikers in poor visibility conditions, at night, when...

Everyone at least once in their life has had to walk in the forest and think about what to do if they get lost. You can navigate the terrain in different ways, there are many ways, the most common are a compass and clearly visible objects in the surrounding...

When navigating the terrain, very often you have to move along predetermined directions, and not along the sides of the horizon. How can a compass help us with this? To move in the chosen direction you will need the ability to calculate...

For correct orientation on the ground and obtaining the desired direction of movement using a compass, it is necessary to determine the magnetic azimuth. Magnetic azimuth is a horizontal angle measured clockwise from the magnetic meridian...

When navigating the terrain on a hiking trip, fishing, or simply when you are in an unfamiliar area, you often have to use not so much knowledge of the cardinal directions as arbitrarily chosen landmarks. To get around…

The word "azimuth" comes from the Arabic "as-sumut", which means "path", "direction". The most commonly used phrases with the word azimuth are the azimuth of a celestial body and the azimuth of an earthly object. Azimuth is...

The image of broken bridges is often used in poetry as a symbol of irresistible forces that do not allow lovers to be together. In life, the raising of bridges occurs at a strictly allotted time and has no romantic reasons. Rivers on which...

Kuzina S.V.

Throughout the development of human society, people have needed to move from place to place. Rivers often prevented this. To cross them conveniently and safely, one had to look for a ford or take a detour. A person who saw fallen trees spanning a river came up with the idea of ​​artificially creating such crossings. At first it was fallen trees, then they came up with devices made from rope. With the advent of the wheel, more reliable and durable structures were required. Thus the idea of ​​bridges was born. The bridge is one of the oldest inventions of mankind. It allows you to overcome obstacles in the form of a pond, ravine, landslide. At the same time, the bridge is a military-strategic facility and one of the most important means of communication.

In the culture of various societies, bridges had a spiritual meaning, which was created not only based on their practical value and understanding of them as important parts of the infrastructure of states. Bridges have also become a symbol of human self-affirmation and overcoming the forces of nature. Today there are more than a million bridges of varying lengths, heights and beauty in the world. It is difficult to overestimate their role in the modern international network of transport flows, their enormous commercial and strategic importance.

One of the regions where today’s transport and transit corridors intersect is Kazakhstan. Acting, due to its geographical location, as an international crossroads of the most important trade routes along the North-South-West-East line, Kazakhstan is of great interest for the development of the economies of Asia and Europe. It is symbolic that in ancient times, caravan routes of the Great Silk Road passed through its lands, which served as a road for cultural and trade cooperation between the peoples of the East and West.

An important transport hub connecting the eastern region of Kazakhstan with large economic regions - Western Siberia, Altai, Mongolia, Western China, as well as other regions of Kazakhstan, is the city of Semipalatinsk (now Semey). This is the second largest city in Eastern Kazakhstan and a major railway junction, located at the intersection of the Turkestan-Siberian Railway, the Irtysh River and numerous highways. Bridges across the Irtysh River, which divides the city into two parts, are of great importance in the city’s transport system. Since its formation, the Semipalatinsk fortress, founded in 1718 as a border and military base, as it grew, became an important trading point between Russia and Kazakhstan, and later between Russia, Central Asia and Western China. Dzungarian Kalmyks, Kokandians, Bukharians, and Tashkentians came to the fortress to trade. Decade after decade, Semipalatinsk, becoming an increasingly important center of transit trade, not only passes through industrial and exotic goods of Russia, China, India, and Central Asia, but also successfully trades with these countries in leather, red yuft, meat, and honey produced in the Irtysh region .

Over time, as the region developed and economic ties expanded, it became necessary to build a large railway connecting Turkestan, Semirechye (today the south of Kazakhstan and part of Kyrgyzstan) and Siberia. The idea of ​​building such a railway line was born back in 1886. It was assumed that the road would strengthen Russia’s military presence in the region bordering China, and would also significantly simplify the export of cotton from Turkestan to Siberia and cheap Semirechensk and Siberian grain to Turkestan. In 1906, money was allocated for the construction of the Barnaul - Semipalatinsk - Verny - Lugovaya - Arys line. In 1907, the first geological and statistical-economic studies were carried out on site. Soon the construction of connecting lines from the Trans-Siberian Railway to Semipalatinsk began, which continued until 1917 and even during the civil war. Some branches were completed under the Bolsheviks in the early 1920s.

Despite the construction of railways in Kazakhstan in the first years of Soviet power, with the beginning of industrialization it turned out that the level of development of railway transport was completely insufficient and could not ensure the development of the entire national economy of the republic. First of all, it was necessary to build a line from Semipalatinsk to Lugovaya - the Turkestan-Siberian Railway. The decision to build Turksib was made at a meeting of the USSR Council of Labor and Defense on December 3, 1926. 1,442 kilometers of rail track were to be laid through mountain rivers, rocky ridges, hot sands along the route Semipalatinsk - Ayaguz - Aktogay - Alma-Ata - Chokpar - Chu - Lugovaya.

Laying the highway involved the construction of several large bridges.

Preparations for construction began in April 1927. On July 15, 1927, the first rails were laid in the north in Semipalatinsk, and on November 2 of the same year, the tracks in the south from Lugovaya station were laid. According to Kazakh custom, in order for a newborn child to grow strong and strong, he is carried through a new yurt. This custom was also applied at the opening ceremony of the construction of the highway. An arch-yurt was erected over the Lugovaya station track, to which the Turksib rails adjoined. A steam locomotive passed through it, announcing the birth of the road with its whistle, then the first rails were laid and the first spikes were driven in. On one side of the arch it was written “Turkestan”, on the other - “Siberia”. On the locomotive fluttered red with the slogan “Give me Siberia!”

Workers for the construction of the highway were hired from many regions of the country. Most of all there were Ukrainians - Kyiv, Cherkassy and Poltava grabbers. Then came the Tambov horse carriers, Nizhny Novgorod and Kursk horse carriers. The Miass and Yenisei tarataechniks worked on rocky soils, and the Yukhnovsky tarataechniks were also famous. The news about the road reached the Kazakhs, and they flocked to the new building, primarily to excavation work.

As D.A. Amanzholova notes, “economic ties between the subjects of the federation, the construction of numerous industrial facilities in previously backward regions, with the accompanying intensive movement of large groups of labor resources, objectively strengthened interethnic integration and civil unity of all ethnic communities.”

The builders of Turksib competed with the team of another extremely important construction project of the first five-year plan - the Dneproges. In general, during the construction of bridges on the Turkestan-Siberian Railway, it was the bridge across the Irtysh in the Semipalatinsk region that became the most important object. Ever since the founding and formation of the city, located on both banks of the Irtysh River, their connection remained a pressing problem. And not only because Zarechnaya Slobodka was located on the left bank, but primarily because the famous trade caravans to Semirechye, Xinjiang and Turkestan were equipped and set off from the left bank. During the construction of Turksib, it was necessary to build a bridge in the shortest possible time. The builders of the highway encountered great difficulties due to the untimely delivery of materials on both the right and left (Zhana-Semeysky) banks. Horse-drawn transport was very expensive, and there were not enough horses and camels. The builders managed to establish a crossing across the Irtysh, first organizing a ferry crossing across the river, and with the onset of winter, an ice crossing. But there was no steam locomotive across the river to open the movement of utility trains. Then a heavy sleigh was built, a steam locomotive was loaded onto it, and a road train of four cars moved across the ice. However, the cable holding the sled from behind could not bear the load and broke. The sleigh rushed quickly, the ice trembled, but did not break. The locomotive was successfully pulled to the steppe shore and placed on the rails. Later, a temporary wooden bridge 300 m long was built across the Irtysh. It was erected in 11 days, and cargo went across the river without transshipment. The cost per ton-kilometer of cargo transportation has dropped sharply. But by March 1929, construction of a permanent railway bridge was completed, built in just 18 months. On May 10, 1929, the first regular passenger train passed from Semipalatinsk to Sergiopol (Ayaguz) across a grandiose bridge across the Irtysh with a total length of more than 600 m. The bridge was built by 850 workers, and one and a half thousand tons of stone were spent on its construction. The work was complex (construction of supports on caissons and manual riveting of spans), and they were carried out in three shifts.

The famous scientist, Doctor of Technical Sciences, Honored Worker of Science and Technology Yu.A. later began his engineering career on the construction of this bridge. Limanov. He completed his pre-graduation internship here, and then, after graduating from the Leningrad Institute of Railway Engineers, he began working as an engineer. His first and very responsible work was the instrumental laying out of supports for spans 109.2 m long (with a river depth of 9-10 m). He understood the responsibility of the task well, was very worried and checked all the measurements several times. Only after the river froze and it became possible to check the correctness of the distances laid out by measurements on the ice, was it established that the instrumental breakdowns were accurate. The metal railway bridge across the Irtysh River at the 657th kilometer of the single-track section Semipalatinsk - Zhana-Semey is the largest on the legendary Turksib. It has become a symbol and mechanism for the change and development of not only economic ties, but also the social psychology and culture of people, and the geopolitical situation throughout Central Asia.

Today, the bridge is a connecting link between Kazakhstan and the Russian Federation, as well as countries far and near abroad. Several dozen trains pass through it every day. Despite its venerable age, the bridge copes with the throughput of this section and ensures the safety of trains at the set speed. According to experts, if the crossing is properly maintained, it will last at least another 100 years.

The history of bridges as the embodiment of intercultural communications in Semey continued at the end of the 20th century. The banks of the Irtysh, in addition to the metal railway bridge, are connected by two more roads. The old road bridge exhausted its service life in the mid-1990s, and there was an urgent need to build a new one. As a result, the first suspension bridge in the CIS was built, once again uniting representatives of different cultures. The project for the construction of a bridge across the Irtysh River, consisting of a suspension bridge, access roads and roads connecting both banks in the city of Semipalatinsk, was proposed by the Japanese company Ishikawajima-Harima Heavy Industries Company, Ltd. (“IHI”). It was implemented by the Japanese company IHI and the Turkish company Alsim Alarko. In fact, representatives from six countries took part in the construction of the unique structure. The international team of bridge builders consisted of Kazakhstanis, Japanese, Turks, British, Chinese and Filipinos. Considering that the bridge's road surface consists of 50% natural asphalt supplied from the famous bitumen lake Peach Lake in Trinidad, we can say that the bridge connected three continents - Asia, Europe and the Caribbean of the Western Hemisphere. It is interesting to note that it was built with funds allocated by the International Fund for Economic Cooperation of Japan and the government of the Republic of Kazakhstan. According to the contract, 42 months were allotted for all work. But the facility was ready in a record time of 30 months, and was opened on October 17, 2000. This bridge is economically viable due to its short construction period, elegant and monumental.

The basis of the structure is a suspension strut bridge with a main span of 750 m long and two approach overpasses of 168 m each. The bridge has two three-lane carriageways, each lane 3.75 meters wide. The suspension bridge in Semey is the only suspension bridge across the river in the CIS and the seventeenth in the world. It has a unique resemblance to the Golden Gate of San Francisco, the London Tower Bridge, and the Bosphorus Bridge.

The commissioning of the bridge made it possible to relieve congestion on the old road bridge in the city, highways of republican and international importance, including the Russian Omsk-Novosibirsk highway leading to the Siberian region of Russia. Both the railway and road bridges of Semey across the Irtysh have long and reliably served economic cooperation, tourist exchange, family ties and all kinds of communication between people of different nationalities and cultures living in Kazakhstan, Russia, and the republics of Central Asia.

Bridges connect roads. Roads connect people.

Considering that both Russia and Kazakhstan geographically occupy a strategic position between the West and the East, their transport communications should become a kind of bridge ensuring fruitful interaction between peoples and states. And therefore, despite the differences and boundaries that exist between us, we need to build bridges that connect people.

And it is important to remember: those who burned bridges behind themselves isolated themselves from the whole world.

Literature:

1 Amanzholova D.A. Soviet ethnopolitics (1929-1941) // Ethnic and religious factors in the formation and evolution of the Russian state. M.: New Chronograph, 2012. pp. 207-262.

2 History of the creation of suspension bridges // URL. http://www.arch-mar.ru/hanging_bridge_history.html

3 History of the construction of Turksib // Railway transport. 1999. No. 10 // http://rzd-expo.ru/history/istoriya_stroitelstva_turksiba/

4 Kropacheva V. Bridge to the 21st century. Bridge of Great Opportunities // Voice of the People. 2000. October 27 // URL. http://www.semsk.kz/archive/2000/bridge6.htm

5 Nauryzbaev K. The largest construction project of the five-year plan // URL. http://komsomol-history.kz/index

6 Pigavaev V. The bridge over the Irtysh is a symbol of the new Kazakhstan // URL. http://flashpress.kz/blog/flash/960.html

7 See: Payne M. “Forge” of the Kazakh proletariat? Turksib, nativization and industrialization during the years of Stalin’s first five-year plan // State of Nations: Empire and national construction in the era of Lenin and Stalin. M.: ROSSPEN, 2011. pp. 273-308.

8.http://www.mamm-mdf.ru/exhibitions/prodoljenie-19281931/(date of access: 07/12/2012).

9. http://vsemee.kz/foto/v/staryj-semipalatinsk ​

10.http://images.esosedi.ru/semipalatinsk_zheleznodorozhnyiy_m/70314409/index.html#lat=50406096&lng=80233792&z=15&mt=1&v=0

11. http://flashpress.kz/blog/flash/960.html

Author Yaul Huseynov asked a question in the section Other things about cities and countries

why are bridges needed? I understand that it’s a stupid question, but I need a conditional meaning: what is a bridge and I got the best answer

Answer from Yoroka[guru]
We arrived at the river; we couldn’t change boats. Edward briefly said everything

Answer from Alex Sokolov[guru]
"Bridge -
1. An engineering structure thrown over an obstacle (river, ravine, road). Consists of supports and spans. The intermediate supports are called bulls, the outer ones are called abutments.
2. In wooden architecture - the ceiling, the floor of a chopped wooden structure."
(Construction Dictionary)
"bridge - BRIDGE, bridge (bridge · region), about the bridge, on the bridge, many bridges, · male.
1. A structure connecting two points on the earth’s surface, separated by water, a ditch or some other thing. obstacle and making it possible to communicate between them. Bridge over the Volga. Drawbridge. Suspension bridge. Pontoon bridge. Drawbridge. Build a bridge. Cross the bridge to the other side. Railroad bridge.
2. transfer Something connecting, serving as an intermediary link between someone and something (book). To build a bridge between two warring camps.
3. An extended position of the body, with the chest facing up and resting on the floor, on the ground with the palms and heels (in athletics; sports). Make a bridge.
4. A platform made of boards, logs, etc., flooring (regional and special). Bridge in the entryway of the hut.
5. Part of the car chassis located above the axles (tech.). Rear axle. Front axle.
6. A special bar on which a number of artificial teeth are fixed (special)."
(Explanatory Dictionary of Ushakov)

Answer from Zorina's faith[guru]
The conditional value is connection.

Answer from 3 answers[guru]

Hello! Here is a selection of topics with answers to your question: why are bridges needed? I understand that this is a stupid question, but you need a conditional meaning: what is a bridge?

Serbian writer Ivo Andrić once said about bridges: “They are more important than houses, they are more holy than churches, because they unite more powerfully. They belong to everyone and benefit everyone equally; they are built precisely in those places where many human needs converge; they are more durable than other buildings and never serve any hidden or evil purpose.” Many millennia ago, people noticed that it was easier to cross a stream along the trunk of a fallen tree that accidentally connected opposite banks. Later they began to specifically cut down trees for laying primitive bridges. They were made from sawn logs or from large flat stones thrown into the water. These were the forerunners of modern reinforced concrete bridges, which either span expressways across deep valleys or float elegantly over rivers and straits in the form of long-span suspension bridges.

A bridge across a river brings together the opposite banks and the people living on them. This symbol of unity is deeply rooted in our consciousness and language. We say “build bridges,” meaning to establish relationships, make friends; or, conversely, “burn your bridges behind you,” that is, exclude any possibility of retreating or changing your decision. In German, “bridge” is Brucke (“brücke”). It is believed that this word is close in origin to the German word “Prugel”, which means “club”, “wooden stick”. The connection of these words reminds us of those distant times when the ancient Germans built special floorings or bridges from logs and branches in order to move along them through marshy places and swamps. The Romans began building bridges from wood and stone in Central Europe. They called their buildings the Latin word "pons", and from it came the French "pont" and the Italian "ponte".

Millennia ago, such precarious rope suspension bridges spanned rushing rivers and deep gorges in the Andes and Himalayas.

Scientific linguists have still not come to an agreement about the origin of the word “bridge” in Slavic languages. However, it lives in all modern Slavic languages, having many derivatives. In Russian it is pavement, platform, paved, perched... Many cities and towns are called Bridges and Zamostya. This word has even penetrated into the language of the automotive industry (the rear and front axles of a car) or, say, into the language of dentists (here a bridge is called a denture). In Islam and many religions of the East, an important role is played by a bridge to the afterlife, shaped like the Milky Way or the arc that the Sun and stars describe, moving across the sky from the point of sunrise to the point of sunset. The deceased, in order to get to the afterlife, must cross such a long narrow bridge, but only good people succeed in this, while the evil ones fall into the abyss.

In Christianity, there is an idea of ​​the rainbow as a bridge between heaven and people, on the top of which Jesus Christ sits as the highest judge

The ancient Germans believed that the rainbow was the road to heaven, intended for chosen people and gods. And in Christianity there is an idea of ​​the rainbow as a bridge between God and man; in medieval images, Christ appears as the supreme judge seated on a rainbow. The head of the Catholic Church, the Pope, also bears the title “Pontiff Maximus,” which means “great bridge builder” and indicates his role as a mediator between Heaven and Earth, and the time of his reign is called “pontificate.” This title dates back to ancient Rome, when the high priest simultaneously served in the temple and supervised the bridges. That is, already in ancient times bridges were looked at as a sacred symbol.

For centuries, people believed that rivers and lakes, dark forests and deep gorges were inhabited by good or evil spirits - demons who sought to harm people and from whom they had to defend themselves with spells and special rituals. And later, already in Christian times, it was necessary to ask for intercession from God or the saints. The ancient Greeks, for example, thought that good nymphs, guardians of life, lived in springs and streams, and in mysterious and sometimes stormy rivers lived powerful, angry river gods, who from time to time demanded human sacrifices. Crossing a river was often quite dangerous, and people explained this by saying that bridges or decks thrown across a stream aroused the special wrath of the river gods. They even made sacrifices to appease them. Therefore, during the construction of bridges, animals and even people were often immured in them, or blood was mixed into the mortar. According to a widespread superstition, a mother who crossed the bridge with her newborn for the first time had to give a ransom for the child and throw a coin into the water. And funeral processions often forded the river instead of using the bridge. People feared that otherwise the deceased might return, turning into a ghost. According to old folk beliefs, all kinds of evil spirits like to hang out on bridges or near them - devils, witches or spirits in the form of animals. In many countries there are so-called “Devil's Bridges”. Their name goes back to a common fairy tale plot: a master building a bridge, having fallen into despair from the complexity of such work, calls the devil for help. The unclean one appears and builds a bridge in one night, but on the condition that he gets the first living creature that crosses it. However, the devil is tricked: the first to cross the bridge is a rooster or a dog.

The bridge as a point of attraction for supernatural forces: the Pope and the devil stretch out their hands over it to each other

In Europe there are many place names that include the word "bridge" in different languages. For example, with the German “brücke” - Osnabrück, Saarbrücken, Zweibrücken, or Bruges in Belgium, Innsbruck in Austria. In English-speaking countries, the names of many settlements end in the English “bridge”, while in France, on the contrary, they begin with the French “pon”. Cities, rivers and bridges are closely interconnected: settlements usually arose where a trade route led to a river, where there was either a shallow place - a ford (in German - “furt”, hence the names of the cities of Frankfurt, Erfurt, Oxenfurt), or a preserved The bridge dates back to Roman times. In the Middle Ages, when most cities arose, bridges were often destroyed due to wars or natural disasters. Back then, travelers had to cross the river in boats. In this they were helped by local residents, who not only transported strangers to the other side, but also offered them accommodation, food and other services, for money, of course. Thanks to this source of income, settlements gradually grew into cities. The townspeople used the river for water supply, for draining wastewater, for protection from enemies, for operating mills, and as a means of communication. Meanwhile, only rich cities could afford the construction of a stone bridge. Sometimes decades passed before it was possible to complete construction with the technical means of that time, and often an unfinished structure was destroyed by a flood or ice drift.

Nature itself created three basic forms of bridges, and the first bridge builders may have only followed her clues. The simplest bridge is a beam bridge. In its primitive form, it is simply a log thrown across a stream. True, a beam made up of beams or a long stone slab did not allow the span - this is the name given to the distance between two supports, or points on which the beam rests - to be large, since the longer the beam, the sooner it could bend under the weight of the load or its own weight , and then collapse. Of course, the beams could be supported by several piles standing next to each other, but this would be too time-consuming and expensive.

It became profitable to build beam bridges only a few decades ago, thanks to the use of new, very durable materials - steel and reinforced concrete. And for centuries, people have used two other types of bridges. The pedestrian and roadway either rested on masonry arches - such bridges were called arched, or was suspended on ropes or cables - then a suspension bridge was obtained.

Basics of bridge construction. The main shapes of bridges are shown at the top, with arrows marking the distribution of forces. Below are the most important special concepts of bridge construction.

Suspension bridges began to be built later than arch bridges. In tropical countries there are plants with long and strong fibers, such as vines. Sometimes such plants hang directly above the stream, as if forming natural bridges. That is why people who lived in those parts learned to cross to the other side of a river or gorge using ropes twisted from plant fibers or rawhide, that is, to make suspension bridges. The simplest of them were arranged like this: two thick ropes stretched in parallel, along which travelers moved, and two thinner ones, stretched higher and serving as a kind of railing. Such bridges were thrown, for example, across deep chasms in certain high mountain regions of the Himalayas and in the country of the Incas in Peru. Even pack animals with heavy luggage balanced over the abyss on such swinging bridges, the length of which sometimes reached 60 m. In the Himalayas you can find a more advanced form of a suspension bridge, in which a deck of planks or bamboo trunks is laid on two parallel ropes. But such flooring still sags. But in modern suspension bridges this decking is located horizontally, and you can even drive across it. It is suspended on the strongest steel ropes to a thick steel cable, which is supported by high pillars - pylons.

Natural arch bridge 34 m high across the river. Ardèche in the south of France. This was probably once the entrance to a collapsed cave.

An example of a stronger, arched bridge also exists in nature itself - these are openings in the rocks. They form in places where the river makes its way under a layer of particularly strong rock. The adjacent parts of the rock are gradually destroyed by water. This natural arched bridge rises in the south of France over the Ardèche River, 60 km from the city of Nîmes. The width of this rock arch is 59 m and the height is 34 m, which is equal to the height of a 10-story building. Even the Sumerians and Egyptians, about 5,000 years ago, erected arched vaults from brick. For a long time, the arch was the only way to create a bridge with a relatively long span out of stone. This is explained by the fact that stones withstand large pressure forces, or compressive forces, and relatively small tensile forces are destructive for a stone.

The cantilever arch is stable in each phase of construction, the traditional arch is stable only after the installation of the castle, or key, stone

How these forces are distributed in the beam can be clearly seen in the model made from a thick block of foam plastic. On its longitudinal side you need to draw several vertical lines with a felt-tip pen at the same distance from each other. This block is placed on top of two book stacks like a bridge. On top of the middle of this miniature bridge you need to put another book, simulating a load. Now, by observing the lines, you can determine the action of the forces in the foam block. On the upper side of the bar, the distances between the lines have decreased - the upper layers have compressed, this is the action of a compressive force. But the lower ones, on the contrary, have moved apart - there are forces acting here that stretch the foam, this is a tensile force. Tensile forces acting in the lower plane of a loaded stone beam lead to the formation of cracks on it, and then to their expansion, as a result of which the bridge may collapse. However, if you stack the hewn stones in layers and in such a way that they form an arch, then they will rest on each other, being subjected to only compressive, but not tensile, forces.

It is believed that the first stone arches were used in the construction of roofs and gate openings. Hewn stones were laid on both sides towards each other so that the top stone hung somewhat over the bottom, but did not fall. The entire structure remains stable due to the fact that the lower stones are subjected to increasing pressure from the upper ones during installation. At the end, these protruding stones converge to form an arch. The traditional arch differs from such cantilever structures made of horizontal layers in that the joints or seams of its wedge-shaped stones are oriented towards a common center. When building such an arch, you should always use circles - a supporting arch, usually made of boards, less often of metal, on which the arch is laid out. During construction, it takes on the weight of the stones and can only be removed after installing the key stone at the highest point of the arch. Only then does the structure become stable. In this case, the two lower stones, or the so-called heels, and the supports of the arch bear the total weight of the entire structure. With this design, each stone is sandwiched between two neighboring ones and cannot, if it becomes loose, simply fall out of the arch.

Previously, builders, when planning the design of a future bridge, could rely only on their own experience and intuition. Over the past two hundred years, engineers have been using increasingly sophisticated methods to pre-calculate the properties of a planned bridge in order to make it more elegant, cheaper and more reliable. These calculations include not only determining the strength of materials and the gravity that this bridge can withstand, or the so-called load-bearing capacity, but also the force with which hurricane winds or water flows act on the bridge.

A great danger also arises if the bridge begins to sway. A simple example: if you carefully walk along a long wooden board that is secured only at the ends, it bends, but does not necessarily break. However, if you fall into a rhythm that coincides with its own vibrations, they increase very quickly (resonance effect), and the board can break. There were cases when the bridge collapsed due to the fact that a column of soldiers marched along it in step. This happened because the rhythm of the steps accidentally coincided with the bridge’s own vibrations. Therefore, before the column entered the bridge, the command was usually given: “Knock down your leg!” There is also the danger of a similar destructive effect on railway bridges, which begin to vibrate under the influence of carriage wheels rotating at a certain speed. But today builders have already learned to reduce this danger to a minimum.

We write and talk a lot about the importance of accessibility of streets and public spaces for people, and in some cities this is even starting to bear fruit. However, for some reason, during the construction or reconstruction of bridges and overpasses, people are completely forgotten, as if this is an exclusive zone for cars. But you and I understand that this is not the case, that bridges are more important for the accessibility of pedestrians and cyclists than simple streets, because as a rule they connect urban areas through physical obstacles and have no alternatives. Alas, judging by the latest all-Russian projects, everything is very bad.

01. Bridge of a healthy person:

02. Addict's Bridge:

03. The differences are visible even from above - the desire to build traffic-light-free roads in several levels, which are typical for suburban routes, and not for the city, in addition to killing inter-district communications, they also take up too much valuable urban land:

04. Project of an overpass in Kirov. Even from the visualization it is clear that they didn’t even think about pedestrians and cyclists (thank you for at least adding a sidewalk on the bridge, which still breaks off right away)

05. What is there to hide, most often designers don’t think about people at all, so they don’t make comfortable sidewalks, but technical passages that you can’t even walk on (hello to the Golden Bridge from Vladivostok). In this regard, the bridge from Rostov-on-Don surprises and pleases:

06. And the new Krasnoyarsk bridge, which seeks to repeat the fate of the Vladivostok Golden Bridge, is upsetting. Although here you still need to try, in principle, to climb it:

07. You can immediately see how people are treated in the city:

08. And this is the projected exit from the chords in Moscow on the street. Ak. Queen. The insanity in the minds of the designers reached the point that they had to lay a separate pedestrian overpass next to the new road:

Everything is very bad, gentlemen. It will do no good to design city facilities with the expectation that pedestrians and cyclists are second-class citizens.

Photos are honestly taken from the Internet