The main elements and dimensions of the bridge in general view (using the example of a reinforced concrete beam bridge).

Bridges are artificial engineering structures that serve to carry a given road or watercourse over various types of obstacles.

Designed to transfer a given road over another road, usually called an overpass (Fig. 1). If the obstacle to this road is a deep ravine, then the embankment that replaces it in this case is called a viaduct. In a number of other cases, replacement of embankments, for example when constructing bridges over streets in cities to carry urban railways, are called overpasses. Designed to carry water flows over various obstacles, they are called aqueducts (if the water flow is a water pipeline) or bridge-canals (if the water flow is a waterway of communication - a canal (Fig. 2).

Bridge structure

The bridge consists of two main parts: supports and spans. Intermediate supports, called bulls, are intended to transfer pressure from the spans to the corresponding underlying foundation; the end supports - abutments - also serve as retaining walls that maintain the pressure of the embankment approaching the bridge. The span structure, which means the totality of all parts except the supports, is intended to transmit the pressure of the payload to the supports.

Bridge classification

In accordance with the type of supports and spans, bridges can be fixed, when both the supports and spans are fixed, and movable, and in the case where there are movable supports and spans, they are called floating; if only part of the span is movable, they are called movable.

Depending on the type of material used in the span structure, there are:

• wooden,
• metal (currently usually steel),
• reinforced concrete and stone, and the latter means both stone itself (from various types of masonry) and concrete.

In accordance with their operational purpose, bridges are divided into

• railway,
• road,
• urban,
• pedestrian,
• aqueduct bridges,
• bridges-canals.

Depending on the nature of the impacts experienced by the supports , bridges can be:

1. beam, when vertical impacts are transmitted from the spans to the supports,
2. arched, when the supports receive oblique influences from the spans, directed to the outside of the span in question,
3. hanging, when the impacts experienced by the supports also turn out to be inclined, but directed inside the span under consideration.

In multi-span bridges, span structures:

1. split, i.e. separate, working independently in each span;
2. continuous, i.e. representing one continuous whole over a number of spans,
3. cantilever, continuously covering one or a number of spans and equipped with parts hanging into adjacent spans - consoles, the ends of which serve as supports for the adjacent beam span structure.

Types and classification of artificial structures

Depending on their service life, bridges can be permanent or temporary. Permanent bridges are designed with the expectation of continuous and year-round operation for many decades. Accordingly, they are built from durable materials - concrete, reinforced concrete, metal, antiseptic wood, stone. Their structures are designed for the highest temporary loads, which are not possible

only in the present, but also in the future period of operation._ Temporary bridges are made lightweight, for a short service life, from less durable and less strong materials, for example, from timber not impregnated with antiseptics, local stone, etc.

Rice. 1.7. Cross section of tunnel linings:

a and c - from monolithic concrete: b from prefabricated reinforced concrete for a tunnel constructed using a closed method: 1 - vault; 2 - walls; 3 - reverse arch; 4 - overlap; 5 - flat tray

A set of structures installed at the intersection of a permanent watercourse by a road is called a bridge crossing. It consists of a bridge, a roadbed adjacent to the abutments, regulatory structures that direct the water flow, retaining and enclosing walls, bank protection fencing structures and others.

The tunnel (Fig. 1.6) is an artificial structure located in the rock mass

According to their purpose, tunnels are divided into transport (railway and road, urban subway tunnels, pedestrian and shipping), hydraulic, urban and mining. The most widespread are transport tunnels, which by location are divided into those located in mountain ranges, underwater tunnels - under rivers, canals, straits, and urban tunnels - under city passages and neighborhoods.

By the nature of construction, tunnels can differ in the method of work: closed - those built without opening the earth's surface above them, and open.

The dimensions and outlines of the internal free space of transport tunnels depend on the size and shape of the rolling stock and the equipment placed in them. The cross-section of subway and railway tunnels (Fig. 1.7) is determined by the size requirements and can be designed for one track or two (tunnels for three tracks are extremely rare). The cross-section of a road tunnel is determined by the category of the road and the number of lanes, as well as other requirements.

Mountain railway and road tunnels are designed according to SNiP 11-44-78; tunnels for subways - according to SNiP - II-40-80.

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History of bridges

Large construction of new railways and highways in the USSR, reconstruction of part of the existing railway. networks, as well as major works on the reconstruction and improvement of cities, led to the large-scale construction of M. Metal bridge structures of the USSR differ sharply from pre-revolutionary ones.

The first bridges built by mankind were wooden and floating. These include those built by Cyrus the Persian on air-filled bags made of thick leather across the Euphrates River in 538 BC. e., Xerxes through the Dardanelles (Hellespont) during a campaign against the Greeks in 481. The latter was about 1 km long and was built on boats connected by linen ropes. In general, floating bridges, which freed people from the very complex work of building supports based on the ground, were known to both the Romans, who used bridges on barrels to build their crossings, and the Chinese, who built crossings on boats connected by iron chains.

Wooden bridges

Wooden bridges on fixed supports also appeared in ancient times; Information has been preserved about a wooden beam - on stone supports, built around the 7th-8th century. BC e. across the Euphrates in Babylon, the wooden bridge of Julius Caesar built in 56 BC. e., Troyan's arched wooden bridge on stone supports across the Danube, built in 104 (Fig. 4). This bridge, with a total length of about 1 km, had 20 stone pillars about 46 m high and arched spans about 52 m long. The remains of a number of pillars of this bridge have survived to this day in Hungary.

After the fall of the Roman Empire, wooden bridge construction stalled in its development for many years, and only in the Renaissance there was a revival in this area again, and during this period the wooden trusses of the Italian engineer Palladio attracted attention (Fig. 5), already very close to modern farms.

In the second half of the 18th century. Self-taught carpenters Grubenmann did a lot in the development of wooden bridge construction, who, in particular, built a bridge across the Limmat River near Wettingen in 1778 (Fig. 6) with a span of 119 m, which has not been surpassed to this day. At the end of the 18th and 19th centuries. In wooden bridge construction, arched bridges have become widespread.

Here we can note the bridges built by the Swiss carpenter I. Ritter across the Kandel River in Bern with a span of 51 m, in Melingen with a span of 48 m (Fig. 7); across the Seine River in Ivry (near Paris), which had 5 different spans slightly above 20 m in size (Fig. 8), built in 1828 and existed until 1881; across the Delaware at Trenton (Fig. 9) with a span of 60 m, built in 1804 and lasting, with some strengthening, 70 years; through the Schuylkill in Philadelphia (Fig. 10) with an opening of 104 m, built in 1813; through the Gascade-Gleen gorge in America (Fig. 12) with a span of 84 m, built in 1849.

In the first, they were hatched in the 30s of the 19th century. In America, spans with end-to-end wooden trusses of a wide variety of systems appeared, which was the impetus for the further development of wooden bridge construction. Of the large number of trusses used at that time in America, plank multi-lattice sist trusses turned out to be especially rational and practically viable. Tauna (Fig. 12), in which the braces were connected to the belts using wooden cylindrical dowels, as well as the Gau farm (Fig. 13), which had block belts connected to each other by cross-shaped wooden block braces and metal strands. Since it was possible to count the braces as working only in compression, the design of the unit in the truss turned out to be very simple: the braces rested on a special nodal pad that was embedded in the belt. Towne trusses and Gau trusses then found very wide application in Europe and in particular in Russia, where, for example, Gau trusses in an improved form (by engineer Zhuravsky) were used in the 40s of the 19th century. during the construction of the Oktyabrskaya Railway bridge.

One of the largest such bridges of this railway (across the Meta River) has 9 continuous spans of 61 m each. Plank trusses such as Town and Gau trusses turned out to be so rational that they are still considered the main ones in wooden bridge construction. In the subsequent period of time, only some of their details changed and improved. It should be noted that in Russia, since the beginning of the 90s, solid plank trusses of the type proposed by engineer. Lembke, which essentially did not differ fundamentally from a farm like Towne.

From the second half of the 19th century, when metal bridges began to spread widely, stagnation began in the field of wooden bridge construction, which was replaced by a slight rise only after the war of 1914-1918. During this period, a number of new types of wooden bridges were developed in the USSR, in particular the Gau truss with a ride at the bottom with a polygonal outline of the upper chord (Fig. 14), the Langer truss (Fig. 15), the truss with a ride at the bottom with a parabolic outline of the upper chord ( Fig. 16), etc. However, the completed spans of all these wooden trusses did not exceed 52.5 m.

The first pedestrian bridge made of Krasnoyarsk aluminum was opened in Tula

The first aluminum bridge in the Central Federal District was put into operation in Tula on Tuesday. The crossing is intended for pedestrians and is located in the area of ​​the Tula Suvorov Military School and the Patriot-Tula military-patriotic park. The project was implemented with the participation of the Aluminum Association. “Pedestrian crossings on highways are traditionally made of metal or reinforced concrete. We experimented with wood and composite materials. Based on what came out of aluminum, this is, of course, space! It is modern, durable and cheap. In addition, quick installation - the structure was assembled and erected within a few hours. All security measures have been observed - surveillance cameras and elevators for people with limited mobility. The bridge is an example of innovative construction, which we plan to practice in the future. We will build such facilities on federal highways. The whole of Russia is in a hurry to follow the Tula region,” said Russian Transport Minister Evgeny Dietrich at the opening ceremony. Aluminum structures for the bridge were manufactured at the Krasnoyarsk Metallurgical Plant. The length of the span is 40 m, the width of the walkway is 3 m. The span and staircase frames are made of aluminum alloys. Aluminum cladding panels and aluminum profile glazing systems were also used in the construction of the bridge. The project will make the Tula region one of the first Russian regions to use these advanced technologies in the field of bridge construction. “Our plans are to develop this section of roads further. We need a modern interchange that will relieve the complex intersection on Lozhevoy Street and the Eastern Bypass. We will definitely implement this project and count on the support of the Russian Ministry of Transport,” said Alexey Dyumin, Governor of the Tula Region. Aluminum is lightweight and durable. During the construction of the bridge, it was not necessary to use heavy construction equipment, and the structure was designed in such a way that they could be assembled by specialists from any bridge-building organizations. When transporting metal by rail, the load on the road network was significantly greater than when transporting by road. All this in the future will simplify the construction of road crossings in Russia. The development of innovations in the aluminum industry, including the creation of a new industry for aluminum bridge construction in Russia, was started more than five years ago by the founder of RUSAL, Oleg Deripaska.

Stone bridges

The first stone bridges were of small spans, and initially they were of a beam system. Stone bridge construction received significant development in the era of the Roman Empire, and semicircular vaults with spans no higher than 34 m and with a fairly significant thickness of supports are used here, which is clearly seen from Fig. 17, depicting a general view of the remains of the Augustus Bridge across the river. Nehru (near Rome); its average span of 34 m had a creeping vault.

During the era of the Roman Empire, a large number of very interesting and largest stone bridges were built, among which are noted: a Roman three-tier aqueduct with spans of up to 24.5 m, a height of 49 m and a length of 260 m; Antioch aqueduct (Syria) 6,700 m long and 62 m high. In the Middle Ages, the stone bridges built by the special religious organization “Bridge Brothers” attracted attention. Members of this organization built such wonderful buildings as across the river. Rhone in Avignon, 600 m long with a maximum span of 33 m, built in 1177-1185; Currently, out of 18 spans, only 4 spans have survived; across the Alla River to Trezzo (1337), the probable outline of which is shown in Fig. 18, which had a span of 72 m, i.e. so large in size that only in the 20th century. he was surpassed; This bridge lasted only 40 years. because it was destroyed during the siege of the castle during which it was built.

From the beginning of the 18th century. With the development of theoretical work in the field of structural mechanics, masonry bridge construction is further developed, following mainly the path of reducing the rise of the arches and the thickness of the supports. Especially much was done during this period in the field of stone bridge construction by the famous Frenchman Perronet, who carried out, in particular, such structures as:

1. Saint-Makhepse, built in 1772-1786. and having an actual flatness of the vaults of 1: 11.2 (according to the project, the flatness was assumed to be equal to 1: 12) and the thickness of the intermediate supports - about 1: 10 spans, formed also by four stone columns connected in pairs (a very bold decision at that time) ;
2. Nemours, built 1795 - 1804, has vaults with a flatness of 1:15.6, the thickness of the bulls in 1:7 spans.

After a period of some calm from the end of the 19th century. again, further development of stone bridge construction is observed, associated with the names, again, of the Frenchman Sejournet and Freycinet. The following should be noted here:

1. across the Isonzo River (Italy) with a span of 85 m, built in 1906,
2. across the Lot River at Villeneuve (France) with a span of 98 m and finally
3. the world's largest concrete concrete de la Caille, built in 1928 and having a design span of 140 m.

Reinforced concrete bridges

The first reinforced concrete bridges appeared less than 50 years ago, and already in 1908 the famous Gmündertobel Viaduct (Switzerland) with a span of 79 m was built, and 20 years later (1930) in France near Brest a reinforced concrete bridge was built with a previously record time in the world's stone and reinforced concrete bridge construction with spans equal to 186. A slightly smaller span (181 m) reinforced concrete was built in 1934 in Transberg (Sweden).

Great successes in reinforced concrete bridge construction have been achieved in the USSR. In particular, we can point to the largest multi-span arched overpasses with spans above 50 m in bridges across the Volga and Dnieper; across the Moscow-Volga canal at Khimki station - a 4-track railway arch bridge with a span of 30 m; city ​​bridge across the Angara in Irkutsk with spans of 80 m; an original design bridge across the Neva in Leningrad with spans of 105 m using tubes filled with concrete; one of the new bridges (Moskvoretsky) in Moscow with a span of 98 m.

The highest transport bridge

Millau Viaduct, France.
Photo: www.globallookpress.com Built in 2004 in France, the Millau Viaduct (Bridge Above the Clouds) was considered the tallest bridge in the world for almost a decade. It is made in the shape of a semicircle with a radius of 20 km and a length of 2560 m. The bridge consists of eight spans and seven concrete supports. Its road surface is raised 270 m above the ground, and one of the towers reaches 341 m at its peak. This is higher than the Eiffel Tower and only 40 m lower than the Empire State Building in New York. The record holder was replaced by the Aizhai Extra Large suspension bridge, 355 m high, opened in 2012 in China.

Metal bridges

Appeared only in the 18th century; in any case, there is reason to believe that the first iron bridge to be built was a pedestrian suspension bridge on iron chains across the river. Tees in England with a span of 21 m, built in 1747. In general, suspension bridges in the second half of the 18th century. began to develop very strongly, especially in America, where by 1809 about 40 bridges had already been built using the system proposed and patented by Finlay. The spans of suspension bridges began to grow very quickly, and in 1826 the Meneisky bridge was already built in England with a span of 177 m.

In Europe, suspension bridges became very widespread in France, where by 1830 there were already 10 bridges across the river. Ron, and in 1834 the Frenchman Chalcy built a suspension bridge in Orenburg with a span of 264 m using a cable formed from individual cables. The transition to cables in suspension bridges, which significantly lightened their weight and made the structure simpler, turned out to be extremely fruitful for suspension bridge construction and was widely developed, especially in America. The introduction of stiffening beams, which significantly increased vertical rigidity, also played a very important role in the development of suspension bridges. The largest suspension bridges built in America are the Brooklyn Bridge (1883) in New York with an average span of 486.5 m. The Delaware Bridge in Philadelphia (1926) with a span of 533 m; Hudsonsky named after Washington in New York (1931) with a span of 1,067.5 m; across Golden Bay to San Francisco (1937) with a span of 1,281 m.

It should be noted that for such large spans the role of the stiffening beam due to the insignificance of the influence of the moving load compared to the influence of the extremely large dead weight is greatly reduced; in particular, in the Hudson Bridge, the stiffening beam is assumed to have a height equal to about the span. The largest suspension bridges built in Europe are the old bridge across the Danube in Budapest (1804) with a span of 200 m, the new one across the Danube in Budapest (1903) named after. Elisabeth with a span of 316 m, a new one across the Rhine in Cologne (1930) with a span of 315 m.

In the USSR, suspension bridges were not widely used.

What types of bridges are there? Part 1. Record

There are two options here - either the bridges built must be drawbridges, or their spans must be so high that river ships can easily pass under them. The “only” question is: what to make such a bridge from?

Concrete or masonry, invented in ancient Rome, did not make it possible to build a bridge of sufficient height. Therefore, arched bridges made of stone or concrete did not allow ships of that time to sail under such a bridge; the span over the water was too low.

Ponte de Tiberio in Rimini Photo: ru.wikipedia.org

But time passed and eventually the necessary, sufficiently durable materials appeared, making it possible for ships to navigate under bridges.

When a lot of cheap iron appeared in the 19th century, architects did not immediately realize that this was an excellent material for buildings, bridges, skyscrapers, and many different structures that were impossible to build without iron. Which architect was the first to notice this?

Bust of Eiffel at the foot of the Eiffel Tower. Photo: ru.wikipedia.org

Gustave Eiffel. The genius of 19th century construction. A man who radically changed the architecture of the construction of various gigantic structures, using iron as the basis of the power frame.

He completed his studies in 1855 and already designed his first bridges based on the use of new materials. He built various structures, bridges, train stations, houses all over the world. In Africa, in Maputo (Mozambique) and Luanda (Angola), in Latin America, in the USA and in Russia. He even took part in the construction of the Statue of Liberty, which stands in front of the entrance to New York Harbor. They designed the power frame of the statue.

In 1880−1884. Eiffel built the Gharabi Viaduct over the Tuyeres River in France. This bridge is arched, but its size amazed the architect’s contemporaries and admires it even in our time. The total length of the bridge reached 564 meters, the main arch had a span of 180 meters and a height of 60 meters. The bridge crossed the valley at an altitude of more than 130 meters. In 1965, the bridge received the title of historical monument.

For that time, this was incredible; using the old technology using masonry, such a structure would have been absolutely impossible to make, which is why the bridge was not even designed here before the introduction of new construction technologies.

Garabi Viaduct. Photo: ru.wikipedia.org

Until the 19th century, bridges were structurally only arched, and the use of steel and reinforced concrete in their construction made it possible to build beam, suspension or combined bridges.

In cases where it was necessary to connect the banks of very deep and wide rivers or the edges of deep canyons or abysses with a bridge, it became possible to build suspension bridges.

In fact, the very first suspension bridges, or bridges on chains, across chasms in Tibet began to be built in the 5th-6th centuries AD by the Chinese. And this technology penetrated into Europe precisely as “Chinese”; in the 18th century, bridges of the “chinoiserie” type began to be built in Europe. The Englishman Finlay even received a patent for the design of chain bridges.

American John Fidley initiated the construction of suspension bridges in the USA at the beginning of the 19th century. They say that in the era “before strength calculations”, approximately until the 1820s, before building a bridge, they built a model of it in a 1:3 ratio and looked at whether it would stand, including under load.

In 1816, the first suspension bridge was built without the use of chains. They were replaced by an iron rope woven from wire. Subsequently, right up to our time, suspension bridges continue to be improved. Instead of chains, ropes began to be used, first from iron, then from steel, then from special grades of steel, specially designed for the construction of bridges. The thickness of the steel ropes gradually increased. First, a method for calculating strength appeared, then a method for calculating fatigue and metal corrosion. The bridges became longer and longer from year to year.

The Brooklyn Bridge, built in 1883, is still beautiful today. And it does not interfere with navigation, since the road surface is raised above the water by 41 meters. The length of the bridge is 1825 meters, and the largest span is 486 meters long.

Brooklyn Bridge Photo: ru.wikipedia.org

The Brooklyn Bridge held the record for the longest for a very long time, but in our time many suspension bridges have been built longer than it.

Since the middle of the 20th century, cable-stayed bridges began to be built. The difference between a suspension bridge on ropes and a cable-stayed one is that in a suspension bridge there are ropes stretched between the pylons, and the road surface is attached to these main power ropes by many smaller ropes. And in cable-stayed bridges, the road surface is attached directly to the pylons using thick ropes - cable stays.

Here, for example, is the Meiko-Chuo cable-stayed bridge, built in the city of Nagoya, Japan. Its length is 1170 meters, and its main span is 590 meters long.

Meiko-Chuo Bridge Photo: ru.wikipedia.org

The photo shows: the cables are attached at one end to the pylon, and their other end is attached directly to the road surface.

The construction of cable-stayed bridges began in the middle of the 20th century. Today, the longest such bridge has been built in Russia. It spans the Eastern Bosphorus Strait in Vladivostok, its main span is 1104 meters long, the road surface is 70 meters above the water surface, and its total length is 3100 meters.

Nowadays, 79 bridges with a span length of over 380 meters have been built. And 36 of them are Chinese. New, longer bridges are being built in China.

But it is believed that steel and reinforced concrete, as materials for building record-breaking even longer bridges, are no longer suitable. To build bridges with a span of 2.5-3 kilometers, even more durable materials are needed.

So far, the strength of the steel ropes is sufficient to hold the roadway at a height of 50-100 meters from the water in a bridge span of a kilometer wide. But when new materials appear, new bridges will become even more delicate, even longer and cheaper to build.

To be continued…

Tags: bridges, construction technologies, Gustave Eiffel, suspension bridges

Beam bridges

They began to develop around the second quarter of the 19th century. During this period, metal beam structures with solid spans closed on all four sides were implemented; An example of such a bridge is the famous Britannia Bridge (1855) with spans of 140 m. This unprofitable use of material had to give way to through trusses. First, they switched to multi-lattice trusses, then multi-braced trusses appeared, which became very widespread in Europe and especially in Russia.

However, the greatest practical use has been since the beginning of the 20th century. received simple triangular and braced trusses without trusses and with trusses. Beam-cantilever trusses proposed by Gerber have become widespread in metal bridge construction. The largest bridges of this system, which are world famous, are the Fort Bridge in England (1889) with a span of 518 m; Quebec across the St. Lawrence River in Canada (1917) with a world record span for beam bridges of 549 m. In the USSR, beam-cantilever bridges were used in both road, city, and railway bridge construction. In particular, the largest bridges (Saratov) across the Volga with a total length of about 1.8 km have in their main part a beam-cantilever system with the largest spans of about 200 m.

The first metal arch bridges were cast iron. After the replacement of cast iron in arched bridges with steel (from approximately the second half of the 19th century), metal arch bridge construction began to develop very quickly in terms of covering increasingly larger spans. Thus, already in 1887, the famous metal Garabi viaduct with a span of 165 m was built in France. The largest metal arch viaduct, built in Hellgetsky, across the East River in New Pork (1917) with a span of 298 m; across the harbor at Sydney in Australia (1931) with a span of 503 m; through the Kil Van Kull Canal (1931) with a span of 511 m.